ESR studies of the valence bond solid state
Hokkaido University1, RIKEN2
Sunghyun Kim1, 2, Yugo Oshima2 and Reizo Kato2
The valence bond solid (VBS) state of the anion radical salt EtMe3P[Pd(dmit)2]2 isstudied by electron spin resonance (ESR) measurements. The anion layer of
EtMe3P[Pd(dmit)2]2 is composed of Pd(dmit)2 dimers which is S=1/2, and the dimers
form an antiferromagnetic triangular lattice. Although the anion layer is expected to be
frustrated, this sample shows a VBS state below 25 K [1]. Hence, we have performed
the ESR measurements of EtMe3P[Pd(dmit)2]2 to study its spin correlations and spin
dynamics.
Firstly, the ESR linewidth shows an unconventional angular dependence, at 4 K which
can only be explained by the lack of interlayer interaction between the Pd(dmit) 2 dimers(Fig. 1). However, this lack of interlayer interaction contradicts with recent ab-initio
calculations. Meanwhile, the integrated intensity of ESR signals, which is proportional to
the spin susceptibility, decreases gradually by lowering the temperature and becomes
constant at 25 K (Fig. 2). This behavior suggests that spin singlet is gradually created bylowering the temperature, but some spins remain below 25 K. We suppose the lack of theinterlayer interaction is due to the long distance between the residual spins. Detailed
analysis of the ESR measurements will be presented and discussed.
[1] M. Tamura and R. Kato, Sci. Technol. Adv. Mater. 10 (2009) 024304.

Fig. 1. Angular dependence
linewidth at 4 K for B//ab-plane.

ofFig. 2. Temperature dependenceof the ESR integrated intensity
for B//b*-axis.

Investigation of magnetic ordered states in the (Nd1-xCax)2Ir2O7
probed by µSR
R. Asih1,2, N. Adam1,3, S. S. Mohd-Tajudin1,3, S. Maeda4, K. Matsuhira4, M. Wakeshima5,
Y. Hinatsu5, A. Miyake6, M. Tokunaga6, I. Watanabe1,2,3,5, T. Nakano2, and Y. Nozue2
RIKEN Nishina Center1, Dept. of Phys. Osaka Univ.2, Universiti Sains Malaysia3,
Kyushu Institute of Technology4, Hokkaido Univ.5, ISSP University of Tokyo6

The correlated electron (U) and nontrivial physics from spin-orbit coupling(SOC) are two two central threads of quantum materials to realize many exotic
phases, such as Axion insulator, Weyl semimetal, and topological Mott insulator [1].
Typical systems which have comparable U and SOC are pyrochlore iridates.
Interestingly, in these pyrochlore systems, U can be systematically tuned bychanging ionic radius of R3+ ion (r) [1]. As r increases, the temperature ofmetal-insulator transition (MIT) gradually decrease, and its boundary lies between R= Nd and Pr [2]. An abundant of emergent quantum states has been theoretically
predicted on the boundary of MIT [1]. Accordingly, to unravel those states, it isnecessary to control U more finely in the MIT critical region, which can be achievedby chemical substitution on Nd2Ir2O7.
In this study, we report the effect of Ca
substitution on the magnetically orderedstate of Ir4+ moments in Nd2Ir2O7
investigated by muon-spin relaxation.
Nd2Ir2O7 shows metallic behavior at hightemperature, and undergoes MIT attemperature of TMI = 33 K [2]. In ourprevious µSR study, we observed theappearance of long-range magneticallyordered state of Ir4+ moments at temperature
cooperated with TMI [3]. The addition of holecarrier via Ca substitution gradually
decreases the magnetic transition (TM), as
well as TMI, and suppresses the onset of
Fig.1. The internal fieldmagnetically ordered state. As shown in thedependence of temperatures in
Figure 1, Ca substitution suppresses the(Nd1-xCax)2Ir2O7
magnetic ordered states Ir4+ moments, while
the additional long-range order of Nd3+ moments appears below 10 K. Detail resultsof the µSR measurements on (Nd1-xCax)2Ir2O7 will be presented in the talk.
References:[1] W. Witczak-Krempa et al., Annu. Rev. Condens. Matter Phys. 5, 57 (2014)[2] K. Matsuhira et al., J. Phys. Soc. Jpn. 80, 094701 (2011).
[3] H. Guo et al., Phys. Rev. B 88, 060411(R) (2013).

Persistent chimera states in nonlocally coupledphase oscillators
Division of Physics, Hokkaido Univ.
Yusuke Suda, Koji Okuda
In the systems of nonlocally coupled identical limit-cycle oscillators, there often appears aninteresting phenomenon called the chimera state. The chimera state is characterized by thecoexistence of coherent and incoherent regions as shown in Fig. 1. The coherent region of thechimera state consists of synchronized oscillators with the identical average frequency, while
the incoherent region consists of not-synchronized oscillators.
We consider the system of nonlocally coupled phase oscillators
j+R
1 ∑θ̇j (t) = ω +Γ (θj (t) − θk (t)),
2R k=j−R(1)where θj (j = 1, . . . , N ) is the phase of ith oscillator, ω is the identical natural frequency and
R is the coupling range. As the 2π-periodic coupling function Γ , the sine coupling Γ (ϕ) =− sin(ϕ + α) is generally used, where α is the phase lag parameter. In the continuous limit
N → ∞, the chimera state is a stable steady state [1]. However, in the finite N cases, thechimera state for the system (1) with the sine coupling is chaotic transient and finally collapse
into the completely synchronous state [2].
In this study, we have investigated the chimera state in the system (1) with the HanselMato-Meunier coupling Γ (ϕ) = − sin(ϕ + α) + r sin(2ϕ), where r is the amplitude ratio of thesecond harmonic component, and obtained the result that the chimera state in the finite N
case can be persistent (nontransient) by the numerical simulation. Details of this study was
already published as [3].

(b) -0.2.
< θj >

θj

(a) π

0

-π

-0.4
-0.6
-0.8

0

500

j

1000

0

500

1000

j

Figure 1: The chimera state for the system (1) with N = 1000. The left figure shows thesnapshot of phase θj , and the right figure shows the profile of the average frequency ⟨θj ⟩.

[1] Y. Kuramoto and D. Battogtokh, Nonlinear Phenom. Complex Syst. 5, 380 (2002).
[2] M. Wolfrum and O. E. Omel’chenko, Phys. Rev. E 84, 015201(R) (2011).
[3] Y. Suda and K. Okuda, Phys. Rev. E 92, 060901(R) (2015).

Induced Charge-Density-Wave in Cu-doped TaSe3
Department of Applied Physics, Hokkaido University
Atsushi Nomura
Induction of states is helpful in understanding their mechanism and searching their
new characters as we can see in high-temperature superconductors and the sulfur
hydride system. If a Charge-Density-Wave (CDW) is induced in materials which do
not exhibit a CDW, new CDW properties might be brought there. Transition metaltrichalcogenides (MX3) are quasi-one-dimensional conductors due to their chain
structure. In most of MX3 (NbSe3, TaS3, NbS3), CDWs occur under the transition
temperature. On the other hand, TaSe3 exhibits no CDW transition. The cause has
been considered that TaSe3 is more three-dimensional than the other MX3
compounds. Conversely considering, if we can expand the distance between chainsand make the dimension lower by doping, a CDW may be induced also in TaSe3.
Therefore, we tried to induce a CDW in TaSe3 by doping Cu. By measuring theresistance as a function of temperature, the dip of the temperature derivative ofresistance was observed in Cu-doped TaSe3, not in pure TaSe3. The dip of thetemperature derivative of resistance indicates a phase transition with the rise ofresistance, suggesting that a CDW is induced in TaSe3 by Cu-doping. The
single-crystal X-ray diffraction pattern (XRD) implies that the a- and c-axis lattice
parameter are expanded and b-axis lattice parameter is contracted by Cu-doping.
The increase of electrical conductivity anisotropy linking with the change of lattice
parameters might make nesting of the Fermi surface good and as a result, a CDW
might be induced.

Magnetic Ground State of CeT2Al10 (T = Ru, Os)
Advanced Meson Science Laboratory, RIKEN Nishina Center
Noraina Adam
The Ce-based compound, CeT2Al10 (T = Ru, Os) is a Kondo semiconductor thatexhibits an unusual high transition temperature at TN ~ 30 K which is still under
debatable [1]. The system shows strong magnetic anisotropy (𝜒a > 𝜒c > 𝜒b) with asmall ordered moment, 0.42 µB which contrarily aligns along the c-axis [2]. In thecase of electron doping by the substitution of Rh for Ru, spin-flop from c-axis toa-axis occurred with a larger amount of magnetic moment, 1.06 µB after 5% of Rh
doping [3]. An investigation by muon spin spectroscopy (µSR) shows a drasticchange of internal field from 170G in CeRu 2Al10 to 780 G after 3% of Rh doping [4].
However, different spin-flop behaviour from c-axis to b-axis was observed in thecase in substitution of 5% La for Ce, (Ce1-xLax)Ru2Al10. The transition temperature
also decreased consistently accompanied by a decrease of magnetic moment as theLa concentration increased more than 7%. Conversely, the same spin-flop behaviour
couldn’t be observed in (Ce1-xLax)Os2Al10 system [5].
We investigated magnetic ground state of (Ce1-xLax)T2Al10 (T = Ru, Os) usingµSR. Both compounds exhibited clear sign of coherent oscillation in the time
spectrum at low temperature confirming the appearance of a long-range
magnetically ordered state Ce moments. However,no critical changes found in the internal fieldsuggesting no spin-flop behaviour occur. In
addition to those experimental efforts, we carriedout computational analysis of muon sites in
CeRu2Al10 and examined the electronic state of
Ce moments around muon in order to study the
spin-flop behaviour.
[1] T. Nishioka et al., JPSJ 78, 123705 (2009)[2] J.-M. Mignote et al., PRB 89, 161103 (2014).
[3] R. Kobayashi et al., JPSJ 83, 104707 (2014).
[4] H. Guo et al, PRB 88, 115206 (2013).
[6] D.T. Adroja et al., PRB 92, 094425 (2015).

Figure 1: Spin structure of Ce-ion
in the magnetically ordered state
estimated from our computational
investigations by using thedensity functional theory.

Intrinsic spatial dependence of superconducting gap inhigh-Tc cuprate Bi2Sr2CaCu2O8+: an STM/STS study
Y. Shibata,1 T. Nonami,1 O. Urata,1 S. Mizuta,1
T. Kurosawa,1 Y. Toda,2 H. Yoshida,1 N. Momono,3 K. Takeyama,4 M. Oda,1 and M. Ido1
1

Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan2
Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan3
Department of Applied Sciences, Muroran Institute of Technology, Muroran 050-8585, Japan
4
Department of Physics, Asahikawa Medical University, Asahikawa 078-8510, JapanOne of the interesting features of Bi-based high-Tc cuprates such as Bi2Sr2CaCu2O8+δ
(Bi2212) is the one-dimensional (1D) superlattice structure along the b-axis (forming a slant angleof 45° from the Cu-Oinplane bond direction), modulating the bond length between the Cu and theapical O (Oapical) atoms of CuO5 pyramids [1], which has been considered to cause a periodic
modulation of the antiferromagnetic (AFM) coupling between Cu-spins J(r) [2]. The 1D superlattice period ~ 26 Å is similar to the superconducting (SC) coherence length of this system; therefore, it may affect local properties of superconductivity [2]. In this study, to clarify the effect ofsuch a superlattice structure on the high-Tc superconductivity, we performed STM/STS experiments on cleaved surfaces of nearly optimal Bi2212 crystals with Tc=90 K and examined the spatial dependence of the SC gap (SCG).
In many cases of STM/STS experiments on Bi2212 cleaved surfaces, STS spectra exhibit a
two-gap structure consisting of a d-wave SCG and a spatially inhomogeneous pseudogap (PG), theso-called “large PG,” whose size varies in nanometer scale over a wide range from an energy of thed-wave SCG amplitude 0 to several times larger one [3, 4]. Furthermore, a checkerboard-typecharge order (CCO) is observed on Bi2212 cleaved surfaces that are accompanied by the inhomogeneous large PG [4]. On some cleaved surfaces used in the present study, however, an STS spectrum consistent with a single d-wave like SCG structure, together with no CCO, was observed atevery measurement point within the areas examined at 8 K. It is characterized by sharp peaks atbias voltages Vs corresponding to the gap edges Vs = ±0/e. This enabled us to examine anddemonstrate the intrinsic spatial dependence of SCG in Bi2212: (1) the d-wave like SCG modulates along the b-axis with the same period as the 1D superlattice or J(r), and (2) the amplitude of
the modulation is ~5% of its average value, which probably suggests a correlation between the
SCG and the AFM coupling of Cu-spins. We will also report a correlation between SCG size and acharacteristic energy of an AFM resonance mode of Bi2212.
References[1] A. Bianconi et al., Phys. Rev. B 54, 4310 (1996)[2] M. Mori et al., Phys. Rev. Lett. 101, 247003 (2008)[3] J. A. Slezak et al., PNAS 105, 3203 (2008)[4] T. Kurosawa et al., Phys. Rev. B 81, 094519 (2010)

Vortex-core charging due to the Lorentz force
in a d -wave superconductor
Department of Physics, Hokkaido University
Hikaru Ueki
We still have quite a poor understanding of the Lorentz force on the supercurrent
and related phenomena. This is because the force on supercurrent itself may easily
be overlooked in the presence of the predominant diamagnetic effect by supercurrent
obeying Ampere’s law. Indeed, the Lorentz force is missing from the standard
Ginzburg-Landau and quasiclassical Eilenberger equations that have been used
extensively to study superconductors theoretically. Hence, physics of the Lorentz
force in superconductors remains mostly unexplored theoretically.
We derive augmented quasiclassical equations of superconductivity with theLorentz force in the Matsubara formalism so that the charge redistribution due tosupercurrent can be calculated quantitatively[1]. Using it, we obtain an analytic
expression for the vortex-core charge of an isolated vortex in extreme type-IImaterials given in terms of the London penetration depth and equilibrium Hall
coefficient. It depends strongly on the Fermi surface curvature and gap anisotropy,
and may charge sign even as a function of temperature due to the variation in the
excitation curvature under the growing energy gap. This is also confirmed in our
numerical study of high-Tc superconductors.

Fig.1

Temperature dependence of thevortex-core charge. n is the electron filling.

[1] H. Ueki et al., JPSJ 85, 064702 (2016).

SR Study Of Organic Superconductor λ-(BETS)2GaCl4
RIKEN Nishina Center and Dept. of Phys. Osaka University
Dita Puspita Sari
The conducting organic system 𝜆-(BETS)2 FexGa1-xCl4 is a hybrid system which
consists of 𝜋 electrons of BETS molecule and 3d ones on Fe ions. In the zero-field
condition, 𝜆-(BETS)2FeCl4 shows the metal-insulator transition at ~8 K and becomessuperconducting with the transition temperature, Tc ≅ 5 K in 33 T, while 𝜆 (BETS)2GaCl4 is superconducting with Tc ≅ 5-6 K even in zero field [1]. In order toachive deeper understanding on those superconducting states, studies on isostructuralλ-(BETS)2GaCl4 are important but less studies have been done on this system [2-3].
Specific heat measurement macroscopically suggested a d-wave pairing symmetry [4].
Accordingly, we carried out muon-spin relaxation (SR) mesurement on λ(BETS)2GaCl4 down to 0.3 K at the RIKEN-RAL Muon Facility.
From zero-field (ZF) μSR, it was foundthat the muon-spin relaxation rate wasindependent of temperature even in the
superconducting state. This means that the
time-reversal
symmetryofthesuperconducting state would not be broken.
Figure 1 shows the temperature dependenceof the muon-spin depolarization ratemeasured in the transverse-field (TF) of 30
G. The TF was applied in perpendicular to
the muon spin direction. The depolarization
rate starts to increase just below TC and havea round shape around 2 K. The tendency
Figure 1. Temperature dependence of thesuggest that it was not simple d-wave nor s- muon-spin depolarization rate measured on λwave.
(BETS)2GaCl4 in the transverse field of 30 G.

References:[1] S. Uji et al., Nature 410, 908 (2001)[2] C. Mielke et al., J. Phys. Cond. Matter. 13, 8325 (2001).
[3] F. L. Pratt et al., Polyhedron 22, 2307-2310 (2003)[4] S. Imajo et al., JPSJ 85, 043705 (2016).

μSR and DFT+U Studies of High-Tc Superconductor
Cuprates
Department of Physics, Hokkaido University
Advanced Meson Science Laboratory, RIKEN Nishina Center for
Accelerator-Based Science
Muhamad Darwis Umar
It is different from conventional superconductors which don’t like magnetics
fields, cuprates superconductor perform the coexistence of magnetism andsuperconductivity [1], and furthermore magnetism in cuprates superconductor
may play role in driving pairing mechanism [2]. Muon-Spin Rotation andRelaxation (SR) is one of most sensitive instruments to study the magnetism ofcuprates supercondutor such as spin-spin correlation, spin density wave, spin
fluctuations and spin-flop transition However, to get more quantitatively
interpretation of SR data, it is needed to know the precisely stopping site on
muon in the material. The estimation of muon site in some cuprates
superconductor material by both Hatree-Fock and Density Functional Theory(DFT) calculations has been done in some previous works [3-6], neverthelessthe studies have not treated yet the materials as strongly correlated system
which exhibits Mott-insulator behaviour.
In our proposed research, we will reinvestigate the muon stopping site incuprates superconductor material by using the Hubbard-rooted Density
Functional Theory (DFT+U) method by Anisimov et al [7,8]. The location
muon in cuprates material is assumed at minimum electrostatic potentials, and it
will be studied for both with or without the change of internal structure cases
taking into account the zero-point energy of muon vibration. We will also study
cuprates material with or without doping to see the dependence of magnetic
order on dopant concentration.
Our expectated results are that besides providing antiferromagnetic insulator
behaviour shown by the existence of gap energy and zero total magnetic
moments as well as the magnetic phases of doped cuprates material, theHubbard correction will also effect the the distribution of spin density, so it willrefine the previous calculation on internal fields.
[1] B. Lake et al., Nature, 415, 299 (2002)[2] T. Hattori et al., Phys. Rev. Lett. 108, 066403 (2012)[3] R. Saito et al., R., Physica C 185-189, 1217-1218 (1991)[4] T. McMullen et al., International Journal of Modern Physics B 5, 1579-1588 (1991)[5] S. B. Sulaiman et al., Phys. Rev. B 49, 9879-9884 (1998).
[6] H. U. Suter et al., Physica B 326, 329-332 (2003).
[7] V.I. Anisimov et al., Phys. Rev. B 44, 943 (1991)[8]. V.I. Anisimov et al., Phys. Rev. B 48, 16929 (1993)

13C NMR study of nonmagnetic insulating phase ofλ-(BEDT-STF)2GaCl4
Department of Physics, Hokkaido University
Y. Saito, T. Yamazaki, S. Fukuoka, N. Matsunaga, K. Nomura,and A. Kawamoto,
Quasi-two-dimensional organic conductors -(BETS)2MCl4 (M=Ga, Fe) [BETS:
C10H8S4Se4] which have attracted attention because, these salts show novel featuresof superconductivity including Fulde-Ferrell-LarkinOvchinnikov (FFLO) andmagnetic field-induced superconductivity (FISC) [1-4]. In -(BETS)2GaCl4, d-wave
SC gap structure was reported by a specific heat measurement[5], however,superconducting (SC) paring mechanism of  salts is still unclear due to lack ofuniversal phase. To clarify what fluctuation the superconductivity mediates instrongly correlated electron system, electron correlation in insulating phase near the
SC phase is important. Recently, it is revealed that insulating phaseof-(BEDT-STF)2GaCl4 [BEDT-STF: C10H8S6Se2] is located in vicinity of
-(BETS)2GaCl4. Therefore, -(BEDT-STF)2GaCl4 is appropriate material forstudying electron correlation in insulating phase.
We investigated magnetic property of insulating phase of -(BEDT-STF)2GaCl4 bysite-selective 13C NMR. Large enhancement of (T1T )−1 was observed below 20 K as
shown in Fig. 1, indicating strong AF spin fluctuation exits. We also observed
anomalous decrease of linewidth,
althoughlong-range
magneticordering did not occur. We willreport the results in more detail inthis presentation.
[1] S. Uji et al., Nature 410, 908 (2001).
[2] L. Balicas et al., PRL 87, 067002(2001).,[3] S. Uji et al., PRL 97, 157001 (2006).
[4] S. Uji et al, PRB 85, 174530 (2012).
[5] S. Imajo et al., JPSJ 85, 043705 (2016).

Fig.1 Temperature dependence of(T1T)-1.

Magnetic property of a honeycomb ruthenate α-RuCl3
investigated by spin polarized muons
A

Advanced Meson Science Laboratory, RIKEN Nishina Center
B
Department of Physics, The Catholic University of Korea
C
Department of Physics, Chung-Ang University
Sungwon YoonA, B
S.-H. DoC, K.-Y. ChoiC, I. WatanabeA, B, and B. J. SuhB

The honeycomb ruthenate, α-RuCl3, was suggested as a candidate to realize Kitaev
spin model with those reasons, such as the cubic environment surrounded by Clions for the strong spin orbit coupling, and honeycomb layers connected by a weakvan der Waals interaction for the ideal two dimensional environment to cause thebond dependent exchange[1].
We synthesized honeycomb ruthenate single crystal. This material shows therhombohedral lattice in the the crystal structure survey, and exhibits the single
magnetic anomaly, 6 K, 9.5 K, and 12.5 K in the DC susceptibility results as shownin Fig. 1. This result is similar with the previous experimental results[2-4].
In order to get the information of details of magnetic behaviors, we carried out µSR
measurements at the RIKEN-RAL Muon Facility with the α-RuCl3 single crystal.
We are going to present the magnetic
ordered behavior around 6 K at zero
field. Also, we will talk about the
spin dynamics of the α-RuCl3 around6 K revealed in the longitudinal fielddependence.
[1] K. W. Plumb et al., Phys. Rev. B, 90,
041112(R) (2014).
[2] Y. Kubota et al., Phys. Rev. B 91,
094422 (2015).
[3] M. Majumder et al., Phys. Rev. B, 91,
180401(R) (2015).
[4] J. A. Sears et al., Phys. Rev. B, 91,
144420 (2015).

Fig.1 Temperature dependence ofDC susceptibilities at various fields.

Magnetic Properties in Organic -d System
λ-(BEDT-STF)2FeCl4
Department of Physics, Hokkaido University
Takaaki Minamidate
Quasi-two-dimensional organic conductor -(BETS)2FeCl4 (BETS =bis(ethylenedithio)tetraselenafulvalene) is well-known as the first organic material
to show magnetic-field induced superconductivity [1]. This salt shows metal-AF
insulator transition at 8.3 K at zero magnetic field [2]. Magnetization measurements
have shown that the Fe+3 ion is found in the S = 5/2 high-spin state, and it has been
believed so far that the metal-AF transition is due to the AF ordering of the Fe
moments. However, based on thermodynamic properties a recent study proposedthat the 3d-spin state is paramagnetic and the pi-spin state is AF ordered [3]. The
questions regarding the mechanism of AF transition are still unanswered.
To elucidate the mechanisms of AF insulating phase, we conducted 1H-NMR andmagnetic susceptibility measurements for -(BEDT-STF)2FeCl4 (BEDT-STF =bis(ethylenedithio)diselenadithiafulvalene), which can be placed at the negative
pressure region of BETS salt. We observed the sharp peak in the 1/T1 andbroadening of the NMR spectrum, which associate to the AF transition, at 16 K. We
also found that the magnetic susceptibility showed a broad peak structure at 8 K and
there was no anomaly at 16 K. Furthermore, in the K- plot, the NMR shift showsthe enormous increasing in AF phase.
We concluded that the spin susceptibility in AF state in these salts can be
explained in the framework with AF ordered -spin system, however, we must take
into account the finite d-d AF interaction toward a detailed understanding of the
behavior of 3d-spin system.
[1] S. Uji et al., Nature 410, 908 (2001).
[2] H. Akutsu et al., J. Am. Chem. Soc. 119, 12681 (1997).
[3] H. Akiba et al., J. Phys. Soc. Jpn. 78, 033601 (2009).

Superconducting pairing gap due to orbital nematic fluctuations
Graduate School of Science, Hokkaido University andNational Institute for Materials Science
T. Agatsuma and H. Yamase
In iron-based superconductors, superconductivity (SC) is realized close to the magnetic
phase [1]. In addition, the so-called electronic nematic phase, which breaks only the orientational symmetry and retains the other symmetries, is usually realized also close to themagnetic phase. As a result, SC occurs closer to the nematic than the magnetic phase. Hencenematic fluctuations are expected to play an important role for SC. As the origin of nematicfluctuations, spin and orbital nematic scenarios are discussed. In this study, we focus on thelatter scenario and study SC from orbital nematic fluctuations.
We already have theoretical works on SC from orbital nematic fluctuations. Yanagi etal. studied Eliashberg equations and found that the symmetry of the superconducting gap
becomes s++ -wave [2]. However, the renormalization of quasiparticles was not considered.
Consequently, obtained Tc became unrealistically high and SC was realized slightly above theonset temperature of the nematic phase, in contrast to experimental observations. Yamaseand Zeyher overcame these drawbacks by including the renormalization function [3]. They
found that orbital nematic fluctuations drive strong coupling SC and Tc becomes comparable
to experimental values, implying that orbital nematic fluctuations can be a new mechanism ofhigh-Tc SC. The superconducting gap is, however, assumed constant on each Fermi surface.
In this study, we develop the analysis of Eliashberg equations by allowing a momentum
dependence of the gap and aim to establish a new high-Tc mechanism from orbital nematicfluctuations. When SC occurs from the tetragonal phase, we find that the superconducting
gap exhibits a weak momentum dependence and can be approximated to be isotropic s++ wave. SC can occur also inside the nematic phase. In this case, the superconducting gap
retains s++ -wave symmetry, but can become highly anisotropic. The momentum dependenceof the gap is understood by considering orbital components on each Fermi surface. We discussa possible relevance to a recent angle-resolved photoemission spectroscopy data [4].

[1] G. R. Stewart, Rev. Mod. Phys. 83, 1589 (2011).
[2] Y. Yanagi et al., Phys. Rev. B 82, 064518 (2010); J. Phys. Soc. Jpn. 79, 123707 (2010).
[3] H. Yamase and R. Zeyher, Phys. Rev. B 88, 180502(R) (2013).
[4] H. C. Xu et al., arXiv:1603.05219.

Theory of magnetic Raman scattering in
antiferromagnetic spin tubes
Department of Physics, Hokkaido University
Takashi Inoue
Magnetic Raman scattering - inelastic photon scattering by magnons - is important probe to
study magnetic excitation of antiferromagnets and there are many experimental observations andtheoretical calculations[1]. Magnetic Raman operator is described as ”photo-induced” exchangeinteraction[2, 3] like equation(1).
R=

∑∑
r

Λδ (êi · δ)(ês · δ)Sr · Sr+δ(1)

δHere, Λδ is proportional to exchange interaction, êi (ês ) is polarization vector of incident(scatterd)
light, δ is the vector which connect the two site, and Sr is spin operator of site r. We evaluate
dynamical correlation function of equation(1).
We investigated magnetic Raman scattering properties of D4h symmetry square prism antiferromagnetic Heisenberg spin tube (FIG.1) by modified spin wave theory[4]. With increase of J∥ /J□ ,where J∥ and J□ are exchange interaction on the tube leg and square plaquette respectively (seeFIG.1), peak positions shift to higher energy side and structure of spectrum changes single peak
to double peak (FIG.2). Changes of the spectrum reflect change of dispersion relation, so we canestimate the magnetic structure of spin tube from B1g mode magnetic Raman spectrum. In thepresentation, we will report more detail which include dependence of polarization direction of light.

FIG.1 Schematic pictureof D4h square prism spin
tube.

FIG.2 Dependence of ratio of exchange interaction J∥ /J□ in B1g mode
magnetic Raman spectrum at T = 0K.

[1] C. M. Canali and S. M. Girvin, Phys. Rev. B 45, 7127 (1992).
[2] P. A. Fleury and R. Loudon, Phys. Rev. 166, 514 (1968).
[3] B. S. Shastry and B. I. Shraiman, Int. J. Mod. Phys. B 5, 365 (1991).
[4] M. Takahashi, Phys. Rev. B 40, 2494 (1989).

Magnetic properties of the molecular bi-layer materials
Hokkaido University1, RIKEN2
Institute for Molecular Science3, The University of Tokyo4
Taehoon Lee1,2, Yugo Oshima2, Hiroshi M. Yamamoto3
Tetsuro Kusamoto4, ReizoKato2

Recently, a novel bi-layer Mott materials, (Et-2,5-DBrP)[Ni(dmit)2]2(Et=ethyl, DBrP=dibromopyridinium) and (Et-2I-5BrP)[Ni(dmit)2]2 (BrP=bro
mopyridinium), have been synthesized [1]. These salts have two crystallographically independent anion layers in the unit cell thanks to the asymmetricshape of the cations and the halogen bonding between the cation and the anion.
The Ni(dmit)2 molecules are strongly dimerized for each layer, and the system
is expected to be a Mott insulator. Actually, these two salts are insulating down
to the lowest temperature. However, its magnetic properties show unconventional features not seen in regular Mott system.
Firstly, both salts do not show any sign of magnetic long-range order.
Secondly, although the temperature dependence of χT for (Et-2,5-DBrP)[Ni(dmit)2]2 shows an antiferromagnetic
property, where χT decreases with decreasing
temperature, the temperature dependence ofχT for (Et-2I-5BrP)[Ni(dmit)2]2 shows more
complex magnetic properties, where thetemperature dependence of χT shows aferromagnetic behavior at low field butchanges to an antiferromagnetic behavior
above 1 T. It is worth to stress that suchdifference of the magnetic properties is justcreated by the small change of cations.
Namely, one bromine of (Et-2,5-DBrP) is justsubstituted by iodine.
It is supposed that the signs of
intralayer and interlayer exchange interactions
Magnetic properties of (Et-2,5-DBrP)[Ni(dmit) ] (top)play an important role in the magnetic
and (Et-2I-5BrP)[Ni(dmit) ] (bottom) by
T. Kusamoto et al. Ref. [1]properties of the bi-layer salts [1]. From thetemperature dependence of χT, it is expected that intralayer exchange couplings
are antiferromagnetic for both salts, but interlayer exchanges are
antiferromagnetic and ferromagnetic for (Et-2,5-DBrP)[Ni(dmit)2]2 and (Et-2I5BrP)[Ni(dmit)2]2, respectively. However, this is just a speculation from themacroscopic magnetic measurements, and microscopic measurements that
directly probe the spins are highly anticipated. Therefore, we will investigate
the bi-layer materials using ESR spectroscopy.
2 2

2 2

[1] T. Kusamoto et al., Inorg. Chem., 51, 11645-11654 (2012).

Muon sites calculation on YBa2Cu3O6
S.S. Mohd-Tajudin,1,2 T. Nishizaki,3 A. Kikkawa,4 N. Adam,1,2 E. Suprayoga,2,5 M.I. Mohamed-Ibrahim,1,2
S. Sulaiman,1 and I. Watanabe.2
12
Universiti Sains Malaysia, RIKEN Nishina Center, 3Kyushu Sangyo University, 4 RIKEN CEMS and5
Institut Teknologi Bandung.

Since the discovery of high-Tc superconductivity, a large number of investigation, bothexperimental and theoretical have been carried out in this exciting field to understand thedifferent aspect of these system. One of the high-Tc superconductivity is YBa2Cu3O6+x (YBCO)
compound and also well known as 123 compound. The electromagnetic properties of YBCO canbe controlled by controlling the oxygen content x. When x = 0, an insulating YBCO inmagnetically ordered state and as we increase the x, magnetic order state disappears andsuperconducting state appear at x > 0.4 and it has a transition temperature Tc of about 90 K.
Previously, neutron diffraction experimental had suggested Cu2 has magnetic moment
0.66µB antiferromagnetically1 and the zero field muon spin rotation and relaxation (ZF-µSR) on
YBa2Cu3O6.2 indicates the existence of long range magnetic order below room temperature hasinternal field 300 G.2 µSR internal field had suggested that muon will stop at two sites, nearapical oxygen and planar oxygen.2
In order to clarify the muon site, we have performed an ab-initio density functional
theory (DFT) calculation for muon implanted in YBCO. We estimated muon site from the view
point of potential energy3 by using VASP program taking into account the relaxation atoms andthe muon sites. Based on the potential calculation, we have calculated the dipole field at themuon site including the relaxation atoms, then the dipole field calculation results will becompared with the internal field at muon sites by experimental.

R

Fig.1 The dipole field model. R is the
distance between muon and the outer atoms.

References[1] J.M. Tranquada et al., PRB, 38, 247 (1988)[2] N. Nishida et al., J. Phys. Soc. Jpn. 57, 597 (1988)[3] B. Adiperdana et al., AIP Con f. Proc. 1554, 214 (2013)

Magnetic Order of π-electrons in the Alkali Metal Superoxide ofCsO 2 studied by the Muon Spin Resonance
Department of Physics, Hokkaido University
Fahmi Astuti
Alkali metal superoxides (AO2) such as NaO2, KO2, RbO2, and CsO2 are ideal model
systems for the study of p-electron magnetism. The KO2 and RbO2 systems havealready been well studied and exhibit antiferromagnetic behavior at the temperatureof 7 K and 15K respectively. However, CsO2 has been less investigated due to thedifficulty in synthesizing samples. All AO2 compounds undergo structural distortions
splitting the degeneracy of the * orbitals and creating an orbitally ordered state.
From an NMR study on CsO2, Tomonaga-Luttinger liquid behavior was suggested
to appear below about 70 K where an antiferromagnetic spin chains is formed as aresult of the p-orbital ordering. A magnetically ordered state is expected to appear
below about 10 K in CsO2 [1,2].
Based on the μSR result, in the ZF condition, the long range magnetic order appear
below 10 K. The frequency of muon spin precession is higher with the decreasing oftemperature indicating the growth of internal field on muon sites. For further
analysis, WIMDA program is used to get the fitting function and some parameter. In
order to get more detail information, the DFT calculation is carried out to estimate
the muon stopping position. There are 2 possible
muon positions around O2- dumbell.
[1] M. Klanjsek, et al.: Phys. Rev. Lett. 115, 057205(2015).
[2] S. Riyadi, et al.: Phys. Rev. Lett. 108, 217206(2012).