QTNS2018

Abstract ( poster)November 7-10, 2018

Program
Wednesday 7
Invitedtalks

11:3012:50
12:5013:00
13:0014:00
14:0015:00
15:0015:30
15:3016:30
16:3017:30
17:3019:00

Thursday 8
9:00Kishine,
9:30
Junichiro
9:30Kato,
9:50
Takeo
9:50Coffee
10:30

Friday 9
9:00- Nakata, Yosuke
9:30
9:30- Aono, Tomosuke
9:50
9:50- Coffee
10:30

10:3011:30

10:30- Otsuka,
11:00 Tomohiro

EntinWohlman,
Ora
Registration 11:30– Yamamoto,
12:00 Kaoru
Opening
12:00- Hatano,
13:00 Naomichi
Moskalet,
13:00- Lunch
Michael
14:00
Aharony,
14:00- Sagawa,Ammon
15:00 Takahiro
Coffee15:00- Shirai,
15:20 Tatsuhiko
Tokura,15:20- Mori,
Yasuhiro
15:40 Takashi
Katsumoto, 15:40- Coffee
Shingo
16:10
Welcome16:10- Kato,
reception
16:30 Akihito
16:30- Phuc,
16:50 Nguyen
Thanh
16:50- Poster
18:00

11:0011:30
11:3011:50
11:5012:50
12:5014:00
14:0015:00
15:0015:30
15:3016:00
16:0016:15
16:1517:15

Shevchenko,
SergeyNakagawa,
MasayaKwek, LeongChuan
Lunch

17:1517:45
17:4518:00
18:0020:00

Uchiyama
ChikakoSummary(Aharony, A)
Banquet

Vacchini,Bassano
Bastidas, Victor
ManuelHashimoto,Kazunari
CoffeeEsposito,
Massimiliano

Saturday 10
10:00- Discussion
10:30 session
10:30- Coffee
11:00
11:00- Discussion
12:00 session

P1
Quantum dissipative dynamics in open systems coupled to hierarchicalenvironments
Yuki Akiyama, Akira Ishikawa, and Kiyoshi Kobayashi
Department of Science for Advanced Materials, University of
Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511, Japan
Quantum dissipation is an elementary process that determines electronic dynamics in a quantum
nanosystem. The electronic system confined in a nanosystem is coupled to a heat bath with infinite
degrees of freedom via a local nanoenvironment with a finite degree of freedom. For example, in thescanning near-field optical microscopy, a nanoprobe is interposed between a nanomaterial and amacroscopic measurement system. In this study, we clarify the effect of such a hierarchical structure of
the environment on the dissipative dynamics in the nanosystem.
We consider a model, as shown in Fig. 1(a). The nanosystem confined in the nanostructure isconsidered to be a two-level system. The nanoenvironment locally coupled to the nanosystem isconsidered to be a twolevel system resonant to the nanosystem. The nonequilibrium behaviour of thenanoenvironment modifies the quantum dynamics in the nanosystem [1, 2]. In this model, quantum
dissipation of the nanosystem is treated theoretically as follows. First, the whole of the nanosystyem andnanoenvironment is exactly treated as a single coupled system, whose coupling rate is g. The energy of
the whole coupled system is dissipated to a heat bath with a dissipation rate γ, whose process is describedby the Lindblad equation. Next, by using the time-dependent projection operators [3, 4], the quantum
dissipative dynamics of only the nanosystem, which includes effects of the hierarchical environments
consisting of the nanoenvironment and heat bath, is derived.
Figure 1(b) shows the dissipative dynamics of population in the nanosystem coupled to thehierarchical environments in cases of γ =0 and γ =10. In the initial state, the populations in thenanosystem and nanoenvironment are 1 and 0.5, respectively. In the case of γ = 0, the nanosystem iscoupled to only the nanoenvironment. The population decreases monotonically and converges to 0.5,
which shows the energy dissipation from the nanosystem to nanoenvironment. In the case of γ =10, thenanosystem is coupled to the hierarchical environments. The population decreases below 0.5 and thenconverges to 0.5 from lower side with nutation, which shows that the dissipation to the heat bath induces
the Rabi oscillation between the nanosystem and nanoenvironment. Thus, it was found that thehierarchical structure of the environment has the important effect on the dissipative dynamics of thenanosystem. Furthermore, we will investigate the effect of the nonequilibrium nature of thenanoenvironment and propose a way to control dissipation of the nanosystem by the nanoenvironment.

Figure 1: (a) Schematic drawing of a theoretical model. (b) Dissipative dynamics of population in ananosystem in cases of γ =0 and γ =10.
References[1] A. Ishikawa, R. Okada, K. Uchiyama, H. Hori, and K. Kobayashi, J. Phys. Soc. Jpn. 87 (2018)
054001.
[2] K. Kobayashi and A. Ishikawa, Prog. Quantum Electron. 59 (2018) 19.
[3] C. R. Willis and R. H. Picard, Phys. Rev. A 9 (1974) 1343.
O. Linden and V. May, Physica A 254 (1998) 411.

P2
Laser-induced DC spin current in Mott insulators
Koki Chinzei, Tatsuhiko N. Ikeda, and Hirokazu Tsunetsugu
The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
In this poster, we report our theoretical work on the DC spin current induced by laser irradiation in
Mott insulators with a noncentrosymmetric lattice structure [1]. To describe the low-energy spin
dynamics in this system, we have started from the Hubbard model in an AC electric field and derived a
Heisenberg model where the exchange interaction oscillates in time by using the Floquet theory. The
time-periodic Heisenberg model describes the exchange process in the extended Floquet Hilbert space[see Fig. 1(a)], and the exchange interaction is given by,
where t0 and U denote transfer integral and on-site Coulomb interaction. Here, we have considered themonochromatic laser, and the Peierls phase is F(t) = F0cosΩt. This result agrees with the previous study[2], which employed the time-dependent canonical transformation.
We have calculated the DC spin current generated by the time-periodic exchange interaction basedon the Floquet-Keldysh formalism. To simplify the problem, we have considered a one-dimensional XY
spin chain coupled to heat bathes of local phonons, and investigated a non-equilibrium steady statedriven by laser. For breaking the inversion symmetry, we have also set both exchange interaction andlocal magnetic field alternating between two values in the chain. As a results, we have found that the
DC spin current is finite when the inversion symmetry is broken and its direction is determined by the
low-energy property of the phonon heat bathes.
These results imply that the laser irradiation induces a DC spin current in Mott insulators withnoncentrosymmetric lattice structure. Its amplitude is also proportional to the fourth of power of thelaser amplitude [see Fig. 1(b)]. In Mott insulators, spin relaxation via conduction electrons is absent, andthis is an advantage for realizing coherent spin transport. Our study may indicate that Mott insulators
are one of the candidate materials of insulator-based spintronics devices.

Figure 1: (a)Illustration of the exchange process of electrons in the extended Floquet Hilbert space.
(b)Laseramplitude-dependence of the DC spin current.

References[1] K. Chinzei, T. N. Ikeda and H. Tsunetsugu, in preparation.
[2] S. Kitamura, T. Oka and H. Aoki, Physical Review B 96 (2017) 014406.

P3
Yusuke Furuya

P4Spectroscopy of double quantum dot spin states by tuning the inter-dot barrier
G. Giavaras and Y. Tokura
Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan

Transport spectroscopy of two-spin states in a double quantum dot can be performed by an ACelectric field which tunes the energy detuning. This has been demonstrated experimentally in different
double dot systems [1, 2]. However, a problem arises when the transition rate between the states is small
and consequently the AC-induced current is suppressed. In our work, we use an exact quantum transportmodel and show that if the AC field tunes the inter-dot tunnel barrier then for large negative detuning,where the spins are in the Heisenberg regime, the transition rate increases drastically resulting in highcurrent. Interestingly, multi-photon resonances are enhanced by orders of magnitude. Our study
demonstrates an efficient way to speedup two-spin transitions [3].
References[1] S. N.-Perge, et al, Phys. Rev. Lett. 108, 166801 (2012).
[2] K. Ono, et al, Phys. Rev. Lett. 119, 156802 (2017).
[3] G. Giavaras, and Y. Tokura, under review

P5
The radio-frequency response of linear arrays of mesoscopic Josephson junctions
G.M. Kanyolo , H. Nishigaki , Y. Mizugaki, H. Shimada
Department of Engineering Science, The University of Electro-Communications,
1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
We performed a quantitative study of the response of linear arrays of mesoscopic Al-AlOx-Al Josephson
junctions to radio-frequency (RF) electromagnetic fields. First, we studied the influence of the RF fields on the I−V characteristics of Cooper-pair tunneling in mesoscopic Josephson junctions. A linear array of Al tunnel
junctions was situated at the end of an RF transmission line at the mixing chamber of a dilution refrigerator at basetemperature of 40 mK, and its dc characteristics measured while a RF voltage was applied through the transmissionline.
We observed the Coulomb blockade (cb) of Cooper-pair tunneling gradually lifted with increase in applied ac
power of the RF field Vac in the sub-gigahertz range irrespective of
its frequency, f (See Figure 1) . This result is dual to microwaveenhanced phase diffusion already observed in a linear array ofJosephson junctions with EJ/Ec > 1 and relatively higher
frequencies of upto 26 GHz.[1]. Our result was resilient to theincrease in the threshold voltage for Cooper pair injection into thearray caused by a high magnetic field H = 500 Oe applied to thesample.
By comparing our experimental results to simulation using thestandard P(E) theory for single junctions (see e.g.[3]), we showthat multi-absorption of low frequency photons (classical limit) bya single junction (via the rest of the circuit acting as theenvironment) leads to Cooper-pair injection into the array thus
lifting the Coulomb blockade. However, a suitable fit to theexperimental results is only possible after extending the standard
P(E) theory The final expression is essentially the time averaged
current result recently proposed in [2] applied to the 1D array ofsmall Josephson junctions within the semi-infinite model[3]. Thus,
our results suggest that accurate low-frequency on-chip RF
field/microwave power detection with 1D arrays of Josephson junctions is possible only after considering thiseffect.
Motivated by this possibility, the RF field emitted by a Figure 1: The Coulomb blockade voltage, Vcb
superconducting single electron transistor (SSET) comprising a - RF field amplitude, Vac dependence forpair of direct current superconducting quantum interference magnetic fields H = 0, 500 Oe extracted fromdevice (dcSQUID) was detected. The linear array of Al tunnel measured I −V characteristics for RF field f =junctions was fabricated adjacent to the SSET at a distance 2 µm 1, 10, 100, 1000 MHz and from their
without any coupling structure. Coulomb blockade was gradually corresponding simulated I−V curves withlifted with increase in applied SSET voltage 0 < V < VJQP = 0.37 Vacsim at a threshold current, Ith = 1 pA andmV where the RF emission by the SSET was through the ac then normalized by their corresponding RFJosephson effect[4] and almost vanished at V = 0.72 mV where free Vcb (0) values.
sequenJQP

tial QP tunneling occurred in the SSET. A similar response of the array was observed for the distance between thearray and the SSET up to 30 µm. As expected, the linear array is demonstrably acting as an on-chip detector of RF
electromagnetic fields.

References[1] S. Liou, W. Kuo, Y. W. Suen, C. S. Wu, C. D. Chen, New J. Phys. 10 (2008) 073025.
[2] H. Grabert, Phys. Rev. B 92 (2015) 245433.
[3] G-L. Ingold, Yu. V. Nazarov / P. Delsing in Single Charge Tunneling: Coulomb Blockade Phenomena
in Nanostructures edited by H. Grabert, M. H. Devoret, NATO ASI Series B: Physics 294 (1992).
[4] P. M. Billangeon, F. Pierre, H. Bouchiat, R. Deblock, Phys. Rev. Lett. 98 (2007) 216802.

P6
Spin-current noise in magnetic bilayer systems
Takeo Kato
Institute for Solid State Physics, The University of Tokyo
In the research field of mesoscopic physics, current noise measurement is an important tool to obtain
useful information on electronic transport such as determination of the effective charge, evaluation ofelectron entanglement, and even spin accumulation. In the research field of spintronics, the pure spincurrent induced by, e.g., spin pumping and spin Seebeck effect (see the left pictures of Fig. 1) is a central
research subject. Recently, the noise of this pure spin current has measured by using the inverse spin
Hall effect [1]. Although the noise of the pure spin current is expected to have useful information, its
theoretical study has, however, been overlooked for a long time, and has just started recently in a few
papers [2, 3].
In this presentation, we consider a normal metal(NM)/ferromagnetic insulator(FI) bilayer system,
which is an important platform of spintronics [4]. Starting with a microscopic spin-exchange model, andusing the secondorder perturbation with respect to the NM-FI interface coupling [5], we derive
expressions of the spin-current noise in terms of the propagators of electrons and magnons. We discuss
how temperature dependences of the spin-current noise contain useful information on the microscopic
mechanism of the spin-current generation (see the right graph of Fig. 1). We conclude that measurementof the spin-current noise indeed provides a powerful tool in research of spintronics.
This study is a joint research with M. Matsuo (Kavli Institute for Theoretical Physics China), Y.
Ohnuma (Kavli Institute for Theoretical Physics China), and S. Maekawa (RIKEN).

Figure 1: (Left) Schematics of spin-current generation by spin Seebeck effect and spin pumping. (Right)
Temperature dependence of the spin-current noise. The temperature is normalized by the Curie
temperature of the ferromagnetic insulator. Temperature dependence of thermal spin-current noise isalso shown.
References[1] A. Kamra, F. P. Witek, S. Meyer, H. Huebl, S. Geprags, R. Gross, G. E. W. Bauer, and S. T. B.
Goennenwein,¨ Phys. Rev. B 90 (2014) 214419.
[2] A. Kamra and W. Belzig, Phys. Rev. Lett. 116 (2016) 146601.
[3] S. Takei and M. Mohseni, Phys. Rev. B 97 (2018) 014427.
[4] M. Matsuo, Y. Ohnuma, T. Kato, and S. Maekawa, Phys. Rev. Lett. 120 (2018) 037201.
[5] Y. Ohnuma, M. Matsuo, and S. Maekawa, Phys. Rev. B 96 (2017) 134412.

P7
Yuki Kawamura

P8
Magnetotransport properties and thermoelectric effect in a device made of Weyl magnet
Mn3Sn
H. Narita A, H. Tomoya A,B, M. Ikhlas A, S. Nakatsuji A,B, Y. Otani A,B,C
ISSP Univ. of Tokyo A, JST CRESTB RIKEN-CEMSC
Recently, Weyl magnets have attracted increasing attention because of their large magnetotransport andthermomagnetic effects, in which the electronic band structure associated with the noncollinear spin configurationis responsible for generating Berry curvature through spin-orbit coupling1. Weyl magnets have also attracted muchattention in the potential application of a new thermoelectric power generation and heat current sensor. The
anomalous Nernst effect (ANE) is a thermoelectric phenomenon typically observed in ferromagnets under theapplication of a temperature gradient, in which a transverse voltage is induced perpendicular to both thetemperature gradients and the magnetization. Recent experimental studies have shown large ANE in a noncollinear
antiferromagnetic metal Mn3Sn with a vanishingly small magnetization2, 3, whose band structure has the Weyl
points near the Fermi level4. The anomalous Nernst effect provides a simple and powerful tool to precisely track
the position and motion of a domain wall propagating. Recent theoretical and experimental studies have shownthat magnetic domains exist in noncollinear antiferromagnetic Weyl magnets5−7.
In this study, we have investigated the anomalous Nernst effect in a microfabricated antiferromagnetic Weyl
magnet Mn3Sn to detect magnetic domains. Focused ion beam (FIB) and lithography were employed tomicrofabricate a thermoelectric device made of Mn3Sn that has a Ta heater with a size of micro order. The
magnetoresistance(MR) of Mn3Sn shows asynmetric behavior in the magnetic field, showing a negative peak anda positive peak for the decreasing and increasing field branch, respectively. According to the results of MR in
magnetic multilayers with perpendicular anisotropy, the contribution of magnetic domains is the origin of theasynmetric MR8. The step structures are also observed in hysteresis of the anomalous Nernst effect. We discuss
the origin of the step structures in the hysteresis and compare the anomalous Nernst effect in the device to that ina bulk single crystal.

References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]

S. Nakatsuji et al., Nature 527, 212-215 (2015).
M. Ikhlas, T. Tomita et al., Nat. Phys. 13, 1085-1090 (2017).
H. Narita et al., Appl. Phys. Lett. 111, 202404-1-5 (2017).
K. Kuroda et al., Nat. Mater. 16, 1090-1095 (2017).
T. Higo et al., Nat. Photon. 12, 73-78 (2018).
J. Liu and L. Balents, et al., Phys. Rev. Lett. 12, 087202 (2017).
X. Li et al., arXiv:1802.00277 (2018).
X. M. Cheng et al., Phys. Rev. Lett. 94, 017203 (2005).

P9

Hydrodynamic approach to electric and energy current in the onedimensional Hubbard model
Yuji Nozawa and Hirokazu Tsunetsugu
The Institute for Solid State Physics, The University of Tokyo

Transport properties of strongly correlated electron systems are not well understood even in exactly
solvable models such as the one-dimensional Hubbard model, which is solved by the nested Bethe ansatz.
In recent years, a hydrodynamic approach for Bethe ansatz solvable models is developed and it is called
generalized hydrodynamics [1, 2]. This approach assumes a local distribution of roots of the Bethe ansatz
equations and describes the time evolution of these distribution functions. Velocities of the roots arederived by the dressing formalism and they depend on types of Bethe roots, which are classified on thestring hypothesis. It enables us to calculate local densities of conserved quantities and associated currents
as local equilibrium values.
We study a two-reservoir quench of the one-dimensional Hubbard model by the generalizedhydrodynamics. The initial state is two semi-infinite thermal equilibrium states joined at the origin (x=0) and we study its time evolution. Between the two states, an intermediate region appears and expands
with time. Local electron density and energy vary with the position x, and their currents flow in thisregion. For the two equilibrium states, we first calculate filling functions of Bethe roots. Local filling
functions at time t are described by those initial values and depend on ray (ξ ≡ x/t). Local conserved
quantities and associated currents are also ray dependent and derived from local filling functions.
We have calculated charge and energy densities and their currents under the two-reservoir quench [3].
We discuss the roles of complex roots corresponding to bound states when the two initial equilibrium
parts have different temperature or chemical potential. In particular, we have considered the case thatthe initial temperature is infinite in one part and found that the charge density does not change in a finite
ξ-region near the boundary of that part although a finite energy current flows there.

tL

x/t = xRO

xFigure 1: Time evolution upon a two-reservoir quench. In the L and R parts, local quantities do notchange from the t =0 equilibrium values on the left and right part, respectively. In the intermediate region,
they vary continuously with depending on the ray ξ = x/t.
References[1] B. Bertini, M. Collura, J. De Nardis, and M. Fagotti, Phys. Rev. Lett. 117 (2016) 207201.
[2] O. A. Castro-Alvaredo, B. Doyon and T. Yoshimura, Phys. Rev. X 6 (2016) 041065.
[3] E. Ilievski and J. De Nardis, Phys. Rev. B 96 (2017) 081118(R).

P10Evaluation of the fluctuation for transport efficiency inquantum transport
Hiroki Okada and Yasuhiro Utsumi
Department of Physics Engineering, Faculty of Engineering, Mie University, Tsu, Mie, 514-8507, JapanThe quantum transport in the view of the quantum thermodynamics of nanoscale circuits, has
attracted much attention. In particular, an issue how to realize high efficiency of heat engine is actively
studied [1, 2]. The efficiency has been extended into general system that multiple input-currents andoutput-currents are involved [3]. In the multi-process transport system, the efficiency is defined as aratio between entropy production rate (EPR) for output currents and that for input currents, which iscalled the exergy efficiency. Then, we call the EPR for the input currents input-exergy, and one for the
output currents output-exergy, respectively. In this work, we focus on the effect of fluctuating currents
flowing thorough a mesoscopic system on the efficiencies. For example, in the nanoscale heat engine,the conversion efficiency between the heat and charge currents can fluctuate because each current
fluctuates. Then, in order to evaluate the fluctuating efficiency of the heat engine, it is useful to consider
the joint probability distribution of the currents and the probability distribution of the efficiency [4, 5].
By using this framework, we calculate the average of the exergy efficiency and find a measurementtime dependence. Within Gaussian approximation, which is associated with linear response regime, we
obtained an inequality that indicates a similar formula of thermodynamically uncertainty relation (TUR)
between the total exergy and the relative uncertainty of each exergy [6]. We will apply our theory to the
Aharonov-Bohm-Casher ring realized by double quantum dot (left panel of Fig. 1). In the system, theAharonov-Bohm effect and the Aharonov-Casher effect are intermixed. By using two effects, we treat
up-spin and down-spin currents as two independent components. We illustrate the result for a case ofspin transport in this model (right panel of Fig. 1).
Figure 1:(Leftpanel)

Schematic picture of the double-dot AB-AC ring. The system consists of two single-level quantum dots,
left (cold) and right (hot) leads. Temperatures and chemical potentials in the left and right leads aredenoted as βL−1/kB, βR−1/kB, µL, and µR, respectively. The charge and spin currents are defined as n↑+ n↓
and n↑ − n↓, respectively. Phases for up-spin and down-spin φσ (σ =↑,↓) are independently regulated byusing AB phase and AC phase. (Right panel) The total exergy (entropy production rate) and relative
fluctuation of the input exergy.
References[1] K. Yamamoto, O. Entin-Wohlman, A. Aharony, and N. Hatano, Phys. Rev. B 94, (2016) 121402.
[2] N. Shiraishi, K. Saito, and H. Tasaki, Phys. Rev. Lett. 117, (2016) 190601.
[3] J.-H. Jiang, Phys. Rev. E 90, (2014) 042126.
[4] M. Polettini, G. Verley, and M. Esposito, Phys. Rev. Lett. 114, (2015) 050601.
[5] H. Okada and Y. Utsumi, J. Phys. Soc. Jpn. 86, (2017) 024007.
[6] T. R. Gingrich, et al., Phys. Rev. Lett. 116, (2016) 120601.

P11
Dissipationless Edelstein effect in insulator-ferromagnet heterostructures
K. N. Okada, Y. Kato, and Y. Motome
Department of Applied Physics, University of Tokyo
Electrical generation and control of magnetic moments are a central subject in the modern field of
spintronics. One of the representative methods intensively studied is the Edelstein effect [1], in which
an electric current flow generates nonequilibrium spin accumulation through a shift of the Fermi surface
in noncentrosymmetric metals with strong spin-orbit coupling, e.g., interface Rashba systems or
topological insulator surfaces [2]. In proximity to a ferromagnetic metal the magnetic moment M (or adomain wall) of the ferromagnet can be manipulated by an electrical current flow, where anonequilibrium spin m induced by the Edelstein effect generates a torque proportional to m×M, termed
the spin-orbit torque. However, the Joule heating by an electric current has been an obstacle, andmagnetization control involving much less dissipation is demanded toward practical applications.
In this study we propose a theoretical framework for current-free Edelstein effect in heterostructuresof a band insulator and a ferromagnet. In contrast to the conventional Edelstein effect, this new
mechanism is immune to impurity scattering as it relies on virtual transitions between the valence andconduction bands. Furthermore, it requires breaking of not only spatial inversion but also time reversal
symmetry. To demonstrate this, we consider a simple two-dimensional band insulator in proximity to aferromagnet [Fig. 1(a)], where the Rashba spin-orbit coupling arises due to the breaking of mirror
symmetry along z axis. Figure 1(b) shows the band structure when the magnetization M in the
ferromagnet points along z axis [Fig. 1(a)], which shows spin splitting by the combination of the Rashba
spin-orbit coupling and exchange coupling to the magnetic moment. By calculating the magnetoelectric
tensor by using the Kubo formula, we discover the manifestation of the dissipationless Edelstein effectdependent on the M configuration [Fig. 1(c)]. Here we define Kij as mi = −µBKijEj, where mi and Ej denote
i component of the magnetization and j component of an external electric field, respectively (µB: theBohr magnton). For instance, when M points along z axis (θ = π/2), an electric field along x axis induces
magnetization along x axis, while it induces magnetization along z axis when M points along x direction(θ = 0). In the presentation we also present the symmetry arguments and the finite-frequency results aswell as the estimation in a hybrid halide perovskite semiconductor as an example of the band insulator.

Figure 1: (a) Schematic picture of the band insulator–ferromagnet heterostructure. The magnetization in
the ferromagnet, M, points along z axis (θ = π/2). m denotes the magnetization induced by thedissipationless Edelstein effect. V represents the applied voltage. Note that no electric current flows (I =0). (b) Band structure of the insulator in the configuration represented in (a), subject to the Rashba spinorbit coupling and exchange coupling to the ferromagnet. The chemical potential µ lies within the bandgap. (c) Magnetoelectric tensor Kij as a function of the M angle θ. θ is defined as Mx = M cosθ and Mz =M sinθ [see also (a)].
References[1] V. M. Edelstein, Solid State Communications 73 (1990) 233.
[2] I. M. Miron et al., Nat. Mater. 9 (2010) 230; A. R. Mellnik et al., Nature 511 (2014) 449.

P12
Rui Sakano

P13
Spin-current induced mechanical torque in a chiral molecular junction
N.
Sasao, H. Okada and Y. Utsumi
Department of Physics Engineering, Mie University, Tsu, Mie, 514-8507, JapanO.
Entin-Wohlman and A. Aharony
Physics Department, Ben Gurion University, Beer Sheva 84105, Israel
Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978,
IsraelRecently, the spin-orbit interaction (SOI) in molecular junctions attracts a lot of attentions since it is considered
to play an important role in electron conduction through chiral molecules. One important consequence induced by
the SOI is the spin-filter effect. Recently the spin-filter effect has been observed in experiments of electric
conduction through chiral molecules, such as DNA molecules [1]. The effect is called the chiral-induced spin
selectivity (CISS) effect. Since such organic molecules do not contain ferromagnetic atoms, it is considered thatthe only possible origin, which causes the CISS effect, would be the SOI. In general, the mass of atomic elements
forming such organic materials are small, and thus the SOI, which is a relativistic effect, is also small. However, a
recent theoretical study demonstrates that in a particular condition, the SOI can be enhanced [2]. Since the electricfield is generated by nuclei forming the molecule, its dynamics would be connected to the dynamics of themolecule. This observation makes possible the conversion of the spin angular momentum to the mechanicalangular momentum. In ferromagnetic materials, such a conversion effect, the gyromagnetic effect, has been known
one century before. Recently, the conversion between the spin angular momentum and the mechanical torque hasreceived attentions again in the spintronics community [3]. In the presence of the SOI, if an injected spin changes
its direction during the transmission process, the angular momentum would be transferred to the atoms as the backaction. Therefore, one can expect that in the molecular junction setups [1], a finite amount of the spin angularmomentum can be converted to the mechanical torque exerting on the chiral molecule, which could induce a rotary
motion of the chiral molecule.
In this presentation, we discuss the mechanical torque exerting on a single-stranded DNA induced by a spinpolarized current. We consider the single-stranded DNA (ssDNA) connected to the source and drain leads. We
adopt a modified tight binding model, in which the SOI is accounted for by the Aharonov-Casher phase. We derive
the spin continuity equation based on a microscopic model Hamiltonian introduced in previous publications, e.g.
[4]. In the presence of the SOI, the total angular momentum is conserved, since the change in the electron spin istransformed into a mechanical torque acting on the molecule. We perform the numerical calculation, and present
that the torque oscillates as a function of the length of the DNA.

Figure 1: (a) Schematic picture of the ssDNA and the chiral molecurlar junction. The ssDNA can rotate aroud thehelical axis due to the mechanical torque. (b) The mechanical torque as a function of the length Nmol for various α,
the strength of the SOI. The energy of the injected electron is fixed as E=0.
References[1] Z. Xie, T. Z. Markus ,S. R. Cohen, Z. Vager, R. Gutierrez, and R. Naaman, Nano Lett. 11, 4652 (2011).
[2] K. Michaeli and R. Naaman, arXiv:1512.03435.
[3] M. Matsuo, E. Saitoh, and S. Maekawa, J. Phys. Soc. Jpn 86, 011011 (2017).
[4] S. Matityahu, Y. Utsumi, A. Aharony, O. Entin-Wohlman, and C. A. Balseiro, Phys. Rev. B 93, 075407(2016).

P14
Ryuta Tezuka

P15
Hydrodynamic optical response of electron fluids in ultrapure metals
Riki Toshio, Kazuaki Takasan, Norio Kawakami
Department of Physics, Kyoto University
The conventional theory of optical response in metals has been based on the Drude theory, which isbased on the assumption that electron-electron scattering is weak enough to ignore and the transport isgoverned by collisions with defects or phonons. However it has become possible, in recent years, toprepare ultrapure metallic samples, such as PdCoO2 [1], graphene [2], and GaAs/AlGaAs
heterostructures [3], where the electron-electron scattering becomes most dominant process governingtransport and the Drude theory is no longer valid. This regime is called ”hydrodynamic regime” anddescribed by an emergent hydrodynamical theory [4]. In fact, several observations of hydrodynamic
effect in DC transport have already been reported[1, 2, 3]. For example, the authors of Ref. [2] havereported evidence of hydrodynamic transport, showing that doped graphene exhibits an anomalous
voltage drop near current injection points, which has been attributed to the formation of whirlpools in
the electron flow. On the other hand, optical response in hydrodynamic regime haven’t been discussed
yet in detail.
In this work, we provide an alternative framework of optical response in hydrodynamic regime.
Based on momentum relaxing Navier-Stokes equation, we calculated the optical conductivity of electron
fluids and discuss how electromagnetic waves propagate in electron fluids. Consequently, we revealed
that, in three-dimensional electron fluids, an electromagnetic wave propagates in two modes due to thenonlocality of electron fluids, which is constrast with the Drude theory, where it propagates in only one
mode. Next, we calculated the reflectance and transmittance in two or three dimensional electron fluids.
This result provides an optical probe of hydrodynamic effect and enable us to measure the viscosity andHall viscosity of electron fluids through simple optical techniques.

Figure 1: Propagation of electromagnetic waves in Drude regime (i) and hydrodynamic regime (ii). In
hydrodynamic regime, two propagation modes exists because of nonlocality of electron fluids.
References[1] Philip J. W. Moll, Pallavi Kushwaha, Nabhanila Nandi, Burkhard Schmidt, Andrew P.
Mackenzie, Science 351 (2016) 1061.
[2] D. Bandurin, I.Torre,R.K.Kumar, M. Ben Shalom, A.Tomadin, A. Principi, G. H. Auton, E.
Khestanova, K. S. NovoseIov, I. V. Grigorieva, L. A. Ponomarenko, A. K. Geim, and M. Polini,
Science 351 (2016) 1055.
[3] L. W. Molenkamp and M. J. M. de Jong, Phys. Rev. B 49 (1994) 5038.
[4] A. V. Andreev, S. A. Kivelson, and B. Spivak, Phys. Rev. Lett. 106 (2011) 256804.

P16
Full-counting statistics of information content and heat quantity in the steady state andthe optimum capacity
Yasuhiro Utsumi
Department of Physics Engineering, Mie University, JapanThe laws of physics limit the performance of information processing. The quantum limits of
information transmission through a quantum communication channel have long been discussed [1]. In
information theory, a model communication system consists of a transmitter, a channel, and a receiver[2] [Fig. 1 (a)]. The physically relevant part is the channel through which a signal produced by thetransmitter reaches the receiver. A measure of the performance of a channel is capacity C, the maximum
possible rate at which information can be transmitted without error. For mesoscopic quantum electric
conductors, the scattering theory was developed to analyze the entropy current as well as the capacity[3]. However, there are not many works in this direction.
Here, we consider a bipartite quantum conductor [Fig. 1 (b)] and analyze the information exchange
between the subsystems [4]. We evaluate fluctuations of self-information associated with the reduced
density matrix of a subsystem subjected to a constraint of the local heat quantity. By exploiting the multicontour Keldysh technique [5, 6], we calculate the R´enyi entropy, or the information generating
function, from which the probability distribution of the conditional self-information is derived. We
present an equality, that relates the optimum capacity of information transmission between thesubsystems and the R´enyi entropy of order 0. We apply our theory to a two terminal quantum dot andanalyze the probability distributions. We point out that at the steady state, the reduced density matrix
and the operator of the local heat quantity of the subsystem may be commutative.
(a )Receiver

ChannelTransmitter

(b )

A

L

D

R

B

Figure 1: (a) A model of the communication system. A transmitter-generated signal is sent through achannel to a receiver. We focus on the signal transmission process through the channel. (b) A quantum
conductor (single-level quantum dot) coupled to the left and right leads. We regard the quantum
conductor as the communication channel. The right lead corresponds to the transmitter, which generates
thermal and shot noise as signals. The left lead corresponds to the receiver side. We regard the left leadas subsystem A and the quantum conductor and the right lead as subsystem B.
References[1] R. Landauer, Science, 272, 1914 (1996); S. Lloyd, Nature, 406, 1047 (2000); J. B. Pendry, J.
Math. A: Math. Gen. 16, 2161 (1983); M. P. Blencowe, and V. Vitelli, Phys. Rev. A 62, 052104(2000).
[2] C. E. Shannon, Bell System Techn. J. 27 379-423, 623-656 (1948).
[3] U. Sivan and Y. Imry, Phys. Rev, B 33, 551 (1986); E. Akkermans, Eur. Phys. J. E 28, 199(2009).
[4] Y. Utsumi, arXiv:1807.04338.
[5] Yu. V. Nazarov, Phys. Rev. B 84, 205437 (2011); M. H. Ansari and Yu. V. Nazarov, Phys. Rev.
B91, 104303 (2015); Phys. Rev. B 91, 174307 (2015); ZhETF, 149, 453 (2016); M. H. Ansari, Phys.
Rev. B 95, 174302 (2017).
[6] Y. Utsumi, arXiv:1804.04328, Phys. Rev. B 96, 085304 (2017), Phys. Rev. B 92, 165312(2015).

P17
Symmetry analysis of electrically-switchable antiferromagnets
Hikaru Watanabe, Youichi Yanase
Department of Physics, Graduate School of Science, Kyoto University
Decades of efforts in the field of spintronics have extensively enhanced the controllability of spinsin electronic devices [1]. The concept of spin electronics is widespread in the field of the condensed
matter physics; e. g. superconductor and topological materials. Recently, the possibility of manipulationsof antiferromagnets is attracting much attention as a novel subfield of spintronics, that is,antiferromagnetic spintronics. Although antiferromagnetic order is seemingly insensitive to external
fields due to its “staggered” nature, recent studies proposed various frameworks of the control of
antiferromagnetic domains by making use of polarized current, spin current, and so on [2]. Especially,
the switching scheme using current-induced antiferroic magnetizations (Antiferromagnetic Edelsteineffect, AFM Edelstein effect) is promising candidate. After theoretical proposals, the domain switchinghas been confirmed experimentally [3, 4]. The experimental works, however, have been achieved in only
a few materials, while physical properties of the AFM Edelstein effect have been clarified by theoreticalworks. Thus, it is highly required for further developments in antiferromagnetic spintronics to explore
more candidate materials.
In our work, we present a symmetry analysis of the domain switching of antiferromagnets. Basedon group-theoretical approaches such as the representation theory and magnetic point groups, we clarify
a criterion for the electrically-switchable antiferromagnets and identify dozens of new candidate
materials. Furthermore, the criterion suggests a link between the switchable antiferromagnets and ferroicalignment of toroidal moments, namely, ferro-toroidic order [5]. We also discuss the emergent propertiesof switchable antiferromagnets derived from the ferro-toroidic order. Those toroidic properties may leadto a complete read-out of the antiferromagnetic domains and promote more elaborate experimental
works in the switchable antiferromagnets.

Figure 1: Correspondence between the antiferromagnetic domains and toroidal moments in CuMnAs,
an candidate material for antiferromagnetic spintronics. The green (purple)-colored arrows represent thetoroidal (magnetic) moments. The electric current stabilizing each domain is depicted.
References[1] Claude Chappert et al., Nat. Mater. 6 (2007) 813; I. Zutiˇ c et al.,´ Rev. Mod. Phys. 76 (2004)
323.
[2] V. Baltz et al., Rev. Mod. Phys. 90 (2018) 015005.
[3] Y. Yanase, J. Phys. Soc. Japan 83 (2014) 014703; J. Zeleznˇ
y et al.,´ Phys. Rev. Lett.
113 (2014) 152701.
[4] P. Wadley et al., Science 351 (2016) 587; S. Y. Bodnar et al., Nat. Comm. 9 (2018) 348.
[5] N. A. Spaldin et al., J. Phy. Condens. Matter 20 (2008) 434203.

P18
Correlation of currents in remote arrays of small Josephson junctions through thequasiparticle excitation
Takuma Watanabe, Yoshinao Mizugaki, and Hiroshi Shimada
The Univerisity of Electro-Communications
Capacitively coupled one-dimensional arrays of small Josephson junctions hold the promise to be used as aprecise current duplicator and multiplier when the arrays are biased near the Coulomb blockade threshold [1, 2],although the mechanism of the current duplication has not been understood sufficiently. We have found that, evena pair of arrays without deliberate coupling capacitances shows a large cross correlation of their currents with theirseparation up to as long as 30 µm, which is considerably greater than their effective mutual Coulomb interaction
distance. This remote correlation of currents would be the basis of the current duplication.
In this study, we shed light on this remote current correlation by investigating the effect of the current in a
onedimensional array of small Josephson junctions on the characteristics of a superconducting single electrontransistor (SSET) fabricated 30 µm apart from the array [ Fig. 1(a) ]. The samples were fabricated with mesoscopic
Al/AlOx/Al junctions, and the array has 20 junctions in series. Measurements were performed by using a compact
dilution refrigerator with a base temperature of 70 mK.
Figure 1(c) shows typical Coulomb oscillations of the SSET with its bias voltage fixed at the superconducting
current peak measured at varied bias voltages, Va, of the remote array. The values of Va are indicated by the dotswith numbers on the current (Ia)–voltage (Va) characteristics of the array in Fig. 1 (b). For the case of small Va inthe Coulomb blockade region (bias points 1–9), 2e periodic Coulomb oscillations were observed in the SSET,
reflecting the Cooper-pair tunneling. However, when a finite current Ia starts flowing in the array with Va raised
beyond these points (to bias points 10–14), the peaks of the current oscillations in the SSET begin to be suppressed.
Raising Va further, the 2e periodic oscillations in the SSET split and eventually get modulated to e periodic
oscillations (bias points above 15).
The observed change from 2e to e periodicity signifies the occurrence of quasiparticle excitation in the electrodesof the SSET induced by the current in the array [3]. When an array is biased near the Coulomb blockade threshold,the generation of nonequilibrium quasiparticles in the electrode will trigger the current through the array [4]. Thus,
the remote current correlation between junction arrays possibly originates from this current-induced remotequasiparticle excitation.

Figure 1: Coulomb oscillations of the SSET with their 2e periodicity modulated to e by the bias voltage of theremote array. Inter-device distance was 30 µm. The measurement temperature was 75 mK. (a) schematic device
arrangement. (b) Ia–Va characteristics of the array. (c) 2e to e modulation of the Coulomb oscillations of the SSET.
References[1] H. Shimada, P. Delsing, Phys. Rev. Lett. 85 (2000) 3253.
[2] K. Takeda, C. Ishida, S. Gandrothula, Y. Mizugaki, H. Shimada, Jpn. J. Appl. Phys. 53 (2014) 023101.
[3] J. Aumentado in Hanbook of Nanophysics: Nanoelectronics and Nanophotonics edited by K. D. Sattler
CRC Press New York (2011) Ch. 16.
[4] I. L. Ho, M. C. Lin, K. Aravind, C. S. Wu, C. D. Chen, J. Appl. Phys. 108 (2010) 043907.

P19
Measurement Superoperator of Balanced Homodyne Detection with Limited Time
Resolution
Yasuhiro Yamada and Tetsuo Ogawa
Department of Physics, Osaka University, Japan
Balanced homodyne detection is widely used to obtain the information on the field quadrature
operator of an optical signal mode, xˆ = aˆ + aˆ†, with aˆ and aˆ† being the annihilation and the creation
operators of the mode. After the signal mode is split into two output modes by a 50/50 beam splitter
mixing with the other input of coherent light with the same frequency, i.e., the local oscillator, the two
outputs are independently detected by two photodetectors (see Fig.1). The difference in detected photon
number during an interval τ, N, is the random variable that is recorded as the outcome of the homodyne
detection. Previous theoretical research shows that the statistical average, E[N], is proportional to thequantum-mechanical average of the quadrature operator, E[N] ∝ ⟨xˆ⟩, in the short interval limit τ → 0[1]. So far, however, their relation regarding higher-order cumulants have not been unveiled
systematically.
Local Oscillator
50/50 Beam Splitter

Detector 1

SignalDetector 2+

Figure 1: Schematic figure of optical balanced homodyne detection. After the signal mode is mixed withthe local oscillator by a 50/50 beam splitter, the two output modes are detected by two different
photodetectors. The difference in detected photon number is recorded.
In actual measurements, the continuous limit is not taken because there is a resolution limit of time.
Taking the resolution limit into account, in this study, we clarify the explicit form of the superoperator
that describes the homodyne detection with a calculation of the nonequilibrium detection dynamics
during finite interval τ. We also obtain the measurement probability distribution of the homodyne
detection from the measurement superoperator. As a result, it is found that while the superoperator has
no direct relation to the projection operator of xˆ, the probability distribution of scaled N given by thesuperoperator is the same as the one of the projective measurement of xˆ except for Gaussian
measurement noise in the case of strong local oscillator. It is remarkable that the variance of themeasurement noise, σ, has a fundamental trade-off relation to the detection loss during τ, L, which is
described by the following equality in the ideal case;σ(eL − 1) = 1.
(1) In the continuous limit of τ → 0, the measurement superoperator reduces to the stochastic quantum
master equation derived by Wiseman and Milburn [1].
References[1] H. M. Wiseman and G. J. Milburn, Physical Review A 47 (1993) 642.

P20
Markovian Quantum Master Equation in the Non-adiabatic Regime
Makoto Yamaguchi
Department of Physics, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan
Tatsuro Yuge
Department of Physics, Shizuoka University, Shizuoka 422-8529, Japan
Tetsuo Ogawa
Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, JapanThe Markovian quantum master equation (QME) plays an important role for the study of nonequilibrium
statistical physics. The structure of this framework is transparent, the generality of its derivation is sufficient,and the approximations applied are well defined, especially when the system Hamiltonian is timeindependent. However, in situations where the system Hamiltonian is time-dependent, there is currently no
general way of rigorously constructing the Markovian QME, despite the growing importance of the quantum
dynamics driven by a time-dependent external field, such as adiabatic quantum computation and quantum
annealing. One possible way to circumvent this difficulty is to assume the slow temporal change of the system
Hamiltonian HˆS(t). In this context, an important assumption employed by many authors is the adiabatic
regime that satisfies the ordinary adiabatic theorem, in which any nonadiabatic transitions are suppressed [1].
There has been thus a wide recognition that the framework is valid only in the adiabatic regime.
Here, we study the conditions to justify the Markovian QME for the time-dependent system Hamiltonian.
By introducing a temporal change time scale for HˆS(t), we then find that the Markovian QME is naturally
derived without the adiabatic theorem. We further find that in a broad range of situations there is no need toeven assume the slow temporal change of HˆS(t) compared to the decay time scale of the bath correlation
function, τB [2].

LZ sweep velocity: v/∆02
Figure 1: (a) The dissipative Landau-Zener model. When the bath is at zero temperature, there is no thermal
excitation and relaxation but only the spontaneous emission can occur due to the vacuum fluctuation. (b) The
transition probabilities. Symbols: the numerical results by the Markovian QME. Solid lines: the exact
probabilities.
As an example, our results are demonstrated in Fig. 1 by applying the framework to the dissipative
LandauZener model, the exact transition probabilities of which are analytically known at zero temperature[3]. In this model [Fig. 1(a)], a system of the Landau-Zener model [] iscoupled with a bosonic bath [HˆB = ∑j ωjˆb†jˆbj] through an interaction Hamiltonian. In Fig. 1(b), the numerical results by the Markovian QME show
good agreement with the exact probabilities even in the nonadiabatic regime. This means that the applicablerange of the Markovian QME is well beyond the widespread belief. Details will be presented at the
symposium.
References[1] A.M. Childs et al., Phys. Rev. A 65 (2001) 012322; T. Albash et al., New J. Phys. 14 (2012) 123016.
[2] M. Yamaguchi et al., Phys. Rev. E 95 (2017) 012136.
[3] M. Wubs et al., Phys. Rev. Lett. 97 (2006) 200404; K. Saito et al., Phys. Rev. B 75 (2007) 214308.

P21
Haruyuki Yamamoto

P22
Enhancement of the superconducting gap induced by dissipation
Kazuki Yamamoto and Norio Kawakami
Department of Physics, Kyoto University
When we consider the effects of dissipation such as loss of particles or inelastic scattering,
Hamiltonian of the system is no longer Hermitian but could be non-Hermitian because dissipation may
cause non-unitary dynamics of the system, leading to the decay of eigenstates. In recent years, nonHermitian quantum systems have been extensively studied both experimentally and theoretically [1–4].
However, most of the previous studies dealt with systems without interaction and there have been few
studies focusing on quantum many-body phenomena.
In this study, we investigate how the BCS superconductivity, a prototypical example of quantum
many-body phenomena, changes its character when the effects of dissipation are taken into account. In
the presence of twoparticle loss, the attractive potential forming Cooper pairs becomes complex. Such asituation can be realized experimentally, for example, as the Orbital Feshbach Resonance (OFR) where
the interaction between the ground 1S0 state and excited 3P0 state in ultracold alkaline-earth atoms
becomes complex because of dissipation. Furthermore, as the experiments to realize superfluids using
OFR by controlling the interaction between different orbitals have been actively conducted these days,
it is particularly important to investigate the stability of superfluids in the system under dissipation. We
calculate the free energy from the partition function using Hubbard-Stratonovich transformation andneglecting quantum and space fluctuations. Then we obtain the gap equation for the dissipative
superconducting system by minimizing the real part of free energy focusing on short-time non-Hermitian
dynamics. From this gap equation, we find a remarkable phenomenon, i.e. unusual enhancement of asuperconducting gap due to dissipation (Figure 1), implying that the attractive interaction forming
Cooper pairs under inelastic scattering is effectively enhanced. We finally show how the BCS meanfield theory in open quantum systems is changed from its Hermitian one and the corresponding
superconducting gap under dissipation is expressed by the expectation value of fermionic operators.
Acknowledgement: This work is done in collaboration with Kazuaki Takasan (Kyoto Univ.), Kyosuke
Adachi (Kyoto Univ.), Masaya Nakagawa (RIKEN), Masahito Ueda (Univ. of Tokyo & RIKEN).

Figure 1: (a) Schematic diagram of the dissipative superconducting model, (b) Variation of the gap size
depending on the complex interaction via dissipation. U1 and U2 represent the real part and imaginary
part of the potential relatively. ∆0 is the superconducting gap.
References[1] A. Guo et al. Physical Review Letters 103 (2009) 093902.
[2] Takafumi Tomita et al. Science Advances 3 (2017) e1701513.
[3] Yuto Ashida, Shunsuke Furukawa, Masahito Ueda, Nature Communications 8 (2017) 15791.
[4] Masaya Nakagawa, Norio Kawakami, Masahito Ueda, Physical Review Letters in press(arXiv:1806.04039.)

P23
Quantum thermodynamics in cavity QED system
Tatsuro Yuge
Department of Physics, Shizuoka University, Shizuoka 422-8529, Japan
Makoto Yamaguchi
Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan
Tetsuo Ogawa
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, JapanThe cavity QED system, which is composed of matter and photons in a cavity, is one of the best
playgrounds for quantum physics. It is also viewed as a thermodynamic system [1, 2] when it is excitedand deexcited by thermal baths as in Fig. 1. In this presentation, we show two results in thethermodynamic cavity QED system, which are concerned with the first and second laws ofthermodynamics, respectively.

Figure 1: A schematic picture of a cavity QED system with thermal baths and a drain (receiving
radiation).
The first result is a decomposition of radiation energy [3]. In the setup shown in Fig. 1, a part ofenergy is transferred from the cavity QED system in the form of radiation. From the thermodynamic
viewpoint, it is of interest to investigate whether this energy transfer is regarded as work or heat. Here,
we provide a proper decomposition into the work and heat, which justifies the intuition that the coherent
part (such as laser) corresponds to work and incoherent one (such as thermal radiation) to heat. We also
show that the energy conservation (the first law) is valid in the decomposition.
The second result is the fluctuation theorem. In the setup shown in Fig. 1, the entropy flow due to(the heat part of) the radiation from the cavity QED system diverges because the drain (an external
system that receives the radiation) is in the vacuum state (zero-temperature state). This causes the naive
fluctuation theorem meaningless. Here, taking the absolute irreversibility [4] (which the current setup
contains) into consideration, we provide a modified fluctuation theorem, which is free from the divergent
entropy flow. We also derive the second-law-like inequality from the modified fluctuation theorem.
References[1] H. E. D. Scovil, and E. O. Shultz-DuBois, Phys, Rev. Lett. 2 (1959) 262.
[2] M. O. Scully, et al., PNAS 108 (2011) 15097.
[3] T. Yuge, M. Yamaguchi, and T. Ogawa, Phys. Rev. E 95 (2017) 022119.
[4] Y. Murashita, K. Funo, and M. Ueda, Phys. Rev. E 90 (2014) 042110; Y. Murashita, et al., Phys.
Rev. A 96 (2017) 043840.