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２０２２年１１月２２日（火）物 理 学 第 一 分 野

物理学第一分野ＤＣ３回生研究発表会
場所：理学研究科５号館 ５階・第４講義室（５２５号室）+Zoom
発表：２０分（別に質問１０分程度）
２０２２年１１月２２日（火）９：００～

開始

目

次

１．Superconducting diode effect in disordered systems
Yuhei Ikeda（ ９：００）・・・・・ １
２．Eigenvalue analysis of amorphous solids consisting offrictional grains under athermal quasistatic shear
Daisuke Ishima（ ９：３０）
・・・・・ ２
３．Generalization of Jordan-Wigner Transformations and Junction Models
Masahiro Ogura（１０：００）・・・・・ ３
１０：３０～１０：４０ 休憩
４．Spin-triplet multiple superconducting phases in UTe2 induced by magnetic field and pressure
Katsuki Kinjo（１０：４０）・・・・・ ４
５．Information flow in turbulence
Tomohiro Tanogami（１１：１０）
・・・・・ ５
６．Anomalous electron hydrodynamics in noncentrosymmetric materials
Riki Toshio（１１：４０）
・・・・・ ６
１２：１０～１３：１０ 昼休み
７．High-harmonics generation in Pr0.6Ca0.4MnO3
Aiko Nakano（１３：１０）・・・・・ ７
８．Theoretical study on dissipative quantum many-body phenomena in ultracold atoms
Kazuki Yamamoto（１３：４０）・・・・・ ８Superconducting diode effect in disordered systems
Condensed Matter Theory Group

Yuhei Ikeda

Abstract The recent discovery of the superconducting diode effect (SDE) has attracted much attention
owing to its intriguing phenomenon. In this work, we describe the intrinsic mechanism of SDE indisordered systems.
© 2022 Department of Physics, Kyoto University

The acquisition of new functionalities in superconductors is essential not only for engineeringdevelopment, such as the creation of more energy-saving devices but also for the development of
the basic science of superconductivity. In recent years, nonreciprocal transport phenomena haveattracted much attention as a new functionality of matter. In the field of superconductivity, thesuperconducting diode effect (SDE) has been observed in [Ni/V/Ta] artificial superlatticesuperconductors with inversion symmetry breaking [1]. The SDE refers to a current flow with zero
electrical resistance in one direction and a finite resistance in the opposite direction. A theoreticalexplanation for the SDE was given in terms of the deparing current [2-5], i.e., SDE by intrinsic
mechanism. Moreover, the theory shows an interesting result suggesting that the sign change of
SDE is closely related to the helical superconductivity [2], in which Cooper pairs are stabilized witha finite center-of-mass momentum. On the other hand, the time-reversal symmetry breaking by anapplied magnetic field violates the assumption of Anderson's theorem, and it is widely known that
impurities have a significant effect on the physical properties of superconductivity [5, 6]. The
evaluation of the effect of impurities on the SDE is interesting not only for the performance
evaluation of superconducting diodes but also for the development of the fundamental theory ofnoncentrosymmetric superconductors.
In this work, we investigate the impurity effect on the SDE
using a microscopic analysis based on the Rashba-Zeeman modeland a self-consistent Born approximation. Our results show thatthe sign change of the SDE disappeared by applying the disorder(see Fig.1). Furthermore, the similarity of the behavior withrespect to impurity concentration supports the existence of acorrespondence between the SDE and helical crossover.
References[1] F. Ando et al., Nature 584, 373 (2020).
[2] A. Daido, Y. Ikeda, and Y. Yanase, Phys. Rev. Lett. 128, 037001 (2022).
[3] J. J. He, Y. Tanaka, and N. Nagaosa, New J. Phys. 24, 053014 (2022).
[4] N. F. Q. Yuan and L. Fu, PNAS 119 (15) e2119548119 (2022).
[5] S. Ilić and F. S. Bergeret, Phys. Rev. Lett. 128, 177001 (2022).
[6] O. Dimitrova and M. V. Feigel’man, Phys. Rev. B 76, 014522 (2007).

Fig. 1. Magnetic field dependence of
the SDE for various impurity
concentration.

Eigenvalue analysis of amorphous solids consisting offrictional grains under athermal quasistatic shear

Physics of Matter and Statistical Dynamics Group

Daisuke Ishima

Abstract We study the two-dimensional amorphous solids consisting of frictional grains under athermal
quasistatic shear. Then, we propose a framework to determine the rigidity by the eigenvalue analysis of
the dynamical matrix. We have confirmed that the rigidity and stress-strain curve by the eigenvalue
analysis agree with the results of simulations.
© 2022 Department of Physics, Kyoto University

Since amorphous materials consisting of dispersed grains such as powders, colloids, bubbles,and emulsions are ubiquitous in nature, to understand their property is important for our daily
life. It is known that amorphous materials behave as fragile solids above a critical density.
The rigidity of amorphous solids is determined with the aid of eigenvalue analysis of Hessianwhich is obtained from the configuration of grains if mutual friction between grain is negligible[1]. In general, however, we cannot
neglect the friction between grains.
Moreover, we realized that the scaling lawof the rigidity with respect to pressure
and strain only for frictional grains [2].
Thus, mutual friction between grains isimportant, but no one has obtained therigidity from the eigenvalue analysis offrictional grains so far.
We have determined the rigidity by the
eigenvalue analysis for frictional grains
with infinitesimal strain with the aid of
the Jacobian matrix [3]. Moreover, if we
restrict our interest to harmonic systems,
we succeed to extend the eigenvalue
analysis even for finite strain. We haveconfirmed that the stress-strain curve
obtained by the eigenvalue analysis
Fig. 1. Plots of the stress-strain curve for 0≤γ≤0.5 for one sample ofalmost perfectly agree with that by thecollection of grains, which includes the results by the eigenvalue
simulation except for the yielding point
analysis (line) and simulation results (filled symbols). The inset is a(see Fig. 1) [4].
close-up of the stress-strain curve in the vicinity of a stress-drop event.
References[1] A. Lemaître and C. Maloney, Phys. Rev. E 74, 016118 (2006).
[2] D. Ishima and H. Hayakawa, Phys. Rev. E 101, 042902(2020).
[3] D. Ishima, K. Saitoh, M. Otsuki, and H. Hayakawa, arXiv: 2207.06632.
[4] D. Ishima, K. Saitoh, M. Otsuki, and H. Hayakawa, in preparation.

Generalization of Jordan-Wigner Transformations andJunction Models
YITP, Solid State Physics, Masahiro Ogura
Abstract In this presentation we discuss our new geometric method for generalized Jordan-Wignertransformations (JWTs). This method includes ordinary JWT for the transverse field Ising model and theredundant Majorana representation for the Kitaev honeycomb lattice model. We also explain someexamples including junction models.

Exactly solvable models have played important roles to understand strongly correlated systems. In
particular, the Jordan-Wigner transformations (JWTs) and their variants (e.g., the redundant Majorana
representations) are well-known and useful methods for solving the 2D classical Ising model, the transverse field
Ising model, and the Kitaev honeycomb lattice model [1,2]. These examples have unveiled many importantphenomena like phase transitions [3].
In this presentation we describe a new method to construct the generalized JWTs [4]. This method is basedon algebras, graph theory and simplicial homology theory. From a given lattice spin Hamiltonian, we canconstruct a graph which reflects its algebraic property. (This graph is called the commutativity graph). If thiscommutativity graph corresponds to some proper simplicial complex, the given Hamiltonian can be transformed
into a Majorana quadratic form, from which the spectrum of the system is calculated.
This method is the visually simple procedure to transform given Hamiltonians into Majorana quadratic
forms. Moreover, it includes the ordinary JWT for the transverse field Ising model and the redundant Majorana
representations for the Kitaev honeycomb lattice model. We also present 1D junction models and calculate their
Majorana zero modes [5].

Fig. 1. Tri-junction models which can be converted into Majorana quadratic forms.

References[1] K. Minami, J. Phys. Soc. Jpn. 85, 024003 (2016).
[2] A. Kitaev, Ann. Phys. (Amsterdam, Neth.) 321, 2 (2006).
[3] L. Onsager, Phys. Rev. 65, 117 (1944).
[4] M. Ogura et al., Phys. Rev. B 102, 245118 (2020).
[5] M. Ogura et al., In preparation.

Spin-triplet multiple superconducting phases in UTe2
induced by magnetic field and pressure
Quantum Materials Lab.

Katsuki KINJO

Abstract The outstanding feature of superconducting (SC) UTe2 is the multiple SC phases by themagnetic field (H) and pressure (P). To investigate the SC properties in these phases, we performed
125
Te-NMR measurements. Our measurements revealed that the spin-triplet state in the P and H-induced
superconductivity is different from that in P = 0.
© 2022 Department of Physics, Kyoto University

In superconductivity, two electrons form a pair called the Cooper pair. Hence, superconductivity isclassified into two categories: spin-singlet or spin-triplet superconductivity. In spin-triplet superconductors, thetotal spin angular momentum S is 1, resulting in the spin and orbital degrees of freedom. Due to these degrees of
freedom, unusual behaviors such as multiple superconducting (SC) phases and magnetic field (H) boosted
superconductivity are expected. However, there are few candidates for spin-triplet superconductors, and thus,
spin-triplet multiple SC phases have not been intensively investigated so far.
In 2018, S. Ran et al. discovered the superconductivity in uranium ditelluride (UTe2) with its
superconducting critical temperature Tc ~ 1.6 K[1]. UTe2 is a leading candidate for the spin-triplet superconductor
because the physical properties are very similar to those in the U-based ferromagnetic superconductors: magnetic
properties and the anisotropy of the upper critical field (Hc2) of superconductivity, especially H-boosted
superconductivity under the b-axis field, and the extremely large upper critical field (Hc2)[1]. Furthermore, recent
nuclear magnetic resonance (NMR) measurements revealed the tiny change or absence of the change in the spin
susceptibility, supporting the spin-triplet scenario[2-4].
In UTe2, multiple SC phases induced by the b-axis high magnetic field above 16 T (HFSC) or pressure
above 0.3 GPa (SC2) are observed as shown in Fig. 1. To investigate the SC properties, especially the spin state inthese phases, we performed the 125Te-NMR measurements under a high magnetic field[5] and high pressure[6].
For high-field measurement, above 20 T, the change in the NMR Knight shift (ΔK) below Tc(H), which is
proportional to the change in the spin susceptibility in the SC state, becomes zero, evidencing the SC spin rotationinduced by the high magnetic field.
Under high pressure, the new SC phases
are observed above 0.3 GPa (SC2, SC3 in Fig. 1),
and superconductivity suddenly disappears
above 1.6 GPa. Our NMR results under pressure
above Tc revealed that the electronic state
dramatically changes above 1.6 GPa, and thatsuperconductivity occurs in the heavy-fermion
state. [6].
Fig. 1 Schematic image of multiple SC phases in UTe2.

References[1] S. Ran et al., Science 365, 684-687 (2019).
[2] G. Nakamine et al., J. Phys. Soc. Jpn. 88, 113703 (2019).
[3] G. Nakamine, KK, et al., Phys. Rev. B 103, L100503 (2021).
[4] H. Fujibayashi, KK, et al., J. Phys. Soc. Jpn. 91, 043705 (2022).
[5] K. Kinjo et al., arXiv:2206.02444, (2022). Submitted to the Phys. Rev. Lett.
[6] K. Kinjo et al., Phys. Rev. B 105, L140502 (2022).

Information flow in turbulence
Nonlinear Dynamics Group Tomohiro Tanogami
Abstract We investigate the nature of information flow in turbulence from an information-thermodynamic
viewpoint. We show that information of large-scale turbulent fluctuations is transferred to small scales
along with energy cascade. Furthermore, we show that information-thermodynamic efficiency is extremely
low compared to other information processing systems such as Maxwell's demon.
© 2022 Department of Physics, Kyoto University

Various phenomena observed in complicated systems such as the earth system and chemical reaction networks
can be regarded as nonequilibrium cooperative phenomena that emerge from many-body interactions. To elucidate
and control the dynamics behind such phenomena, it is pertinent to focus on information transfer between
components constituting the system. Particularly in mesoscopic systems affected by thermal fluctuations, the natureof such information transfer can be described by information thermodynamics. Information thermodynamics isessentially stochastic thermodynamics for subsystems and provides constraints that are consistent withthermodynamics on the exchange of heat and information between subsystems [1]. Recently, it has been applied to
information processing at the cellular level in biological systems and even to deterministic chemical reaction
networks.
Turbulent cascade can be regarded as a nonequilibrium cooperative phenomenon that emerges from extremelycomplicated interactions, where energy is transferred conservatively from large to small scales. This phenomenon
can be described intuitively as the successive generation of smaller vortices by the stretching of larger vortices.
Along with the energy cascade, fluctuations of small-scale quantities follow those of large-scale quantities with atime delay 𝜏" , which corresponds to the characteristic time scale for the largest eddies to be stretched into smaller
eddies. This phenomenon suggests that information on turbulent fluctuations is also transferred from large to small
scales. While turbulence has been studied in various contexts from such an information-theoretic viewpoint overrecent decades, the nature of the information flow associated with turbulent cascade has not yet been elucidated. In
particular, no previous studies have considered the effects of the thermal fluctuations that are inherent in fluids on
information transfer, even though the thermal fluctuations can affect the turbulence dynamics significantly [2].
Here, we aim to elucidate the nature of information flow in turbulence from an information-thermodynamic
viewpoint [3]. To this end, we employ the framework of fluctuating hydrodynamics to explicitly take thermal
fluctuations into account. Specifically, we use the shell model with thermal noise, which is a simplified caricatureof the fluctuating Navier-Stokes equations. This approach not only enables us to obtain fundamental constraints on
information flow, but also allows comparative studies with other information processing systems.
We show that information of large-scale eddies is transferred to small scales along with the energy cascade(Fig. 1). The information transfer rate is characterized by 𝜏" . Furthermore, we numerically show that the
information-thermodynamic efficiency is extremely low
Energy cascadecompared to other information processing systems such as"learning"
Maxwell's demon. This result implies that transferring
information from large to small scales involves enormous
destruction
thermodynamic costs, indicating the poor performance of
turbulence as an information processing system.
Fig. 1. Schematic of information flow in turbulence.
References[1] J. M. Parrondo, J. M. Horowitz, and T. Sagawa, Nat. Phys. 11, 131 (2015).
[2] D. Bandak, N. Goldenfeld, A. A. Mailybaev, and G. Eyink, Phys. Rev. E 105, 065113 (2022).
[3] T. Tanogami and R. Araki, arXiv: 2206.11163.

Anomalous electron hydrodynamics
in noncentrosymmetric materials
Condensed Matter Theory Group,

Riki Toshio

Abstract We formulate electron hydrodynamic theory for noncentrosymmetric materials and propose
several unconventional transport phenomena, such as asymmetric Poiseuille flow. Furthermore, weinvestigate the interplay quantum geometry and surface plasmons on periodic grating nanostructures,
thereby providing a promising route toward a novel type of highly sensitive, broadband terahertz
photodetectors.
© 2022 Department of Physics, Kyoto University

At low temperatures, in some ultraclean metals, the electron mean free path of collisions with impurities andphonons becomes much larger than that of electron-electron scatterings and the sample size. Under this condition,
electron-electron scattering becomes the most dominant process governing electron transport, giving rise to theformation of a viscous flow of an electron fluid [1]. This regime is called “hydrodynamic regime” where theelectron dynamics is described by an emergent hydrodynamic theory. Recently, such hydrodynamic behaviors
have already been reported through several DC transport experiments in clean metals, such as graphene [2], GaAs
quantum wells [3], and Weyl semimetal WP2 [4]. Interestingly, in the past few years, symmetry of crystals andquantum geometry gives a new twist to the concept of electron hydrodynamics, leading to rich and novelhydrodynamic phenomena such as anisotropic or Hall viscosity effects [5-7].
In this presentation, we firstly develop an electron hydrodynamic theory for noncentrosymmetric metals, wherea novel class of electron fluids is realized by lowering crystal symmetries and resulting geometrical effects [8,9].
The obtained hydrodynamic theory suggests an interesting analogy between electron fluids in noncentrosymmetricmetals and chiral fluids in vacuum, and predicts novel hydrodynamic phenomena, that is, asymmetric Poiseuilleflow and anomalous edge current.
Next, we investigate an interplay between quantum geometrical effects and surface plasmons through surface
plasmonic structures, based on the obtained theory [10]. We demonstrate that the quantum nonlinear Hall effectcan be dramatically enhanced over a very broad range of frequency by utilizing plasmonic resonances andnear-field effects of grating gates. Furthermore, we clarify a universal relation between the photocurrent inducedby the Berry curvature dipole and the optical absorption, which is essential for computational material design oflong-wavelength photodetectors. We also discuss a novel mechanism of geometrical photocurrent, which
originates from an anomalous force induced by oscillating magnetic fields and is described by the dipole momentof orbital magnetic moments of Bloch electrons in the momentum space. Our theory is relevant to 2D quantum
materials such as layered WTe2 and twisted bilayer graphene, thereby providing a promising route toward a novel
type of highly sensitive, broadband terahertz photodetectors.

References[1] M. Polini and A. K. Geim, Physics Today 73, 28 (2020).
[2] D. A. Bandurin et al, Science 351, 6277 (2016).
[3] M. J. M. de Jong and L. W. Molenkamp, Phys. Rev B 51, 13389 (1995).
[4] J. Gooth, et al, Nat. comm. 9, 4093 (2018).
[5] P. Rao and B. Bradlyn, Phys. Rev. X 10, 021005 (2020).
[6] G. Varnavides et al., Nature Communications 11, 4710 (2020).
[7] H. Funaki, R. Toshio, and G. Tatara, Phys. Rev. Research 3, 033075 (2021).
[8] R. Toshio, K. Takasan, and N. Kawakami, Phys. Rev. Research 2, 032021 (2020).
[9] R. Sano, R. Toshio, and N. Kawakami, Phys. Rev. B 104, L241106 (2021).
[10] R. Toshio and N. Kawakami, arXiv:2209.10160 (2022).

High-harmonics generation in Pr0.6Ca0.4MnO3Solid state spectroscopy group

Aiko Nakano

Abstract Investigating which degrees of freedom is crucial in nonlinear optical process for stronglycorrelated materials is attractive. Here, we show the enhancement of the high-harmonics intensity with anincreasing charge-ordering gap energy in Pr0.6Ca0.4MnO3. Our results suggest the significance of thecorrelation between different degrees of freedom in nonlinear optical process.
© 2022 Department of Physics, Kyoto University

Intensity (arb. units)

10
10
10
10
10
10
10
10

2

10

294K
7K

3rd

1

6
5
4

8

0

Intensity (arb. units)

10

5th

-1
-2
-3

7th

-4

3
2

TCO〜240K

1

6
0

100

200

300

Intensity (arb. units)

In strongly correlated materials, a single electron picture is not good approximation due to strong correlation
among multiple degrees of freedom, which induces various intriguing states. High-harmonics generation (HHG)
gives an experimental platform to find out a novel nonlinear optical process and understand the role of strong
correlation effect beyond the mean field theory [1].
Manganese oxides are typical strongly-correlated materials which exhibit various phase related to spin, charge,
and orbital degrees of freedom by tuning physical parameters such as temperature and chemical substitution. For
example, Pr0.6Ca0.4MnO3 presents the charge-orbital ordered (CO-OO) state below 240K, and the CE-type
antiferromagnetic (AFM) spin ordered state below 50K [2]. Such a characteristic of manganese oxides enables us
to investigate the relation between multiple degrees of freedom and nonlinear optical properties comprehensively.
Here, we measured the high harmonic signals from Pr0.6Ca0.4MnO3 in a temperature range across the criticaltemperatures of the CO-OO and the AFM transitions. Figure 1 shows high harmonic spectra at 294K (dotted blackline) and 7K (solid blue line). The intensities of HHG are suppressed at high temperature above transition
temperatures. The inset of Fig. 2 shows third order harmonic signal as a function of temperature. Third harmonic
signal shows a gradual decrease below TCO and has a kink just above TCO. We found the increase of the third
harmonic intensity is proportional to the square of the gap energy [3] as shown in Fig. 2. The enhancement of the
HHG intensity with gap opening was also reported for Mott-insulating state in Ca2RuO4 previously [1]. In thepresentation, we will discuss the role of strong correlations in the nonlinear optical process.

Temperature (K)

4

2
-5
-6

0

0.5

1.0

1.5

2.0

2.5

Photon Energy (eV)Fig. 1. High harmonic spectra in the single crystal of
Pr0.6Ca0.4MnO3 at 294K (dotted black line) and 7K (solid
blue line.) The driving photon energy is 0.26eV and theintensity at the focus point is around 0.3TW/cm2.

0.00

0.10

0.20

0.30

Gap Energy (eV)Fig.2. The correlation between the third harmonics
intensity and the gap energy [3]. The inset shows thetemperature dependence of the third harmonics intensity
in a range from 7K to 295K.

References[1] K. Uchida, G. Mattoni, S. Yonezawa, F. Nakamura, Y. Maeno, and K. Tanaka, Phys. Rev. Lett. 128, 127401, (2022).
[2] Y. Tokura, Rep. Prog. Phys. 69, 797 (2006).
[3] Y. Okimoto, (1998). A spectroscopic study of the metal-insulator transition in perovskite-type manganites. (Doctoral
thesis, Department of Physics, University of Tokyo). Available from UTokyo Repository.

Theoretical study on dissipative quantum many-body phenomena
in ultracold atoms
Kazuki Yamamoto, Condensed Matter Theory Group
Abstract Recent progress in ultracold atoms has enabled control of dissipation as well as flexible tuning ofphysical parameters. Motivated by such backgrounds, we investigate several representative quantum
many-body phenomena in ultracold atoms with dissipation, focusing on Fermi-Hubbard models, fermionictight-binding chains, and quantum spin systems.
© 2022 Department of Physics, Kyoto University

In recent years, open quantum systems have been actively studied both experimentally and theoretically. In
many cases, coupling to the environment causes decoherence of quantum states and it is often detrimental to theircontrol. Remarkably, dissipation can also be instrumental in the preparation of novel states in open quantum
systems. To date, a lot of studies have been done by using dissipation such as particle loss, dephasing, andmeasurement backaction, and it is reported both theoretically and experimentally that dissipation can realize
unique nonequilibrium phenomena. On the other hand, many-body effects, which are known to bring about richphenomena induced by correlation, have not been fully understood yet in nonequilibrium quantum systems
subject to dissipation.
In our study, we have explored the following three topics by introducing dissipation, which is relevant tocold-atom experiments:(a) Non-Hermitian (NH) fermionic superfluidity and nonequilibrium dynamics of dissipative fermionicsuperfluids induced by two-body loss of Cooper pairs [1, 2],(b) Rectification physics in nonequilibrium steady states induced by dissipation [3],(c) Universal properties of dissipative Tomonaga-Luttinger (TL) liquids [4].
First, on topic (a), we have analyzed a NH BCS Hamiltonian and developed a NH BCS theory to obtain a NH
gap equation for order parameters, which induces unconventional reentrant phase transitions unique to NH
systems. Then, we have analyzed loss-induced dynamics of dissipative fermionic superfluids by studying the
Lindblad master equation. We have demonstrated that when dissipation is introduced to one of the two superfluids
coupled via a Josephson junction, it gives rise to a nonequilibrium dynamical phase transition characterized by thevanishing dc Josephson current. Then, on topic (b), we have shown that unidirectional particle transport can ingeneral occur when a Lindblad operator is reciprocal provided that the inversion symmetry and the time-reversal
symmetry of the microscopic Hamiltonian are broken. Finally, on topic (c), we have uncovered that NH XXZ spin
chain in the massless regime with weak dissipation belongs to the universality class characterized by thecomplex-valued TL parameter, which is related to the complex generalization of the c = 1 conformal field theory.
In this presentation, we first introduce the overview and advancement of ultracold atoms with dissipation, andthen explain our results concentrating on topic (a).
References[1] K. Yamamoto, M. Nakagawa, K. Adachi, K. Takasan, M. Ueda, and N. Kawakami, Phys. Rev. Lett. 123,
123601 (2019).
[2] K. Yamamoto, M. Nakagawa, N. Tsuji, M. Ueda, and N. Kawakami, Phys. Rev. Lett. 127, 055301 (2021).
[3] K. Yamamoto, Y. Ashida, and N. Kawakami, Phys. Rev. Research 2, 043343 (2020).
[4] K. Yamamoto, M. Nakagawa, M. Tezuka, M. Ueda, and N. Kawakami, Phys. Rev. B 105, 205125 (2022).