Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Araki, Yasufumi; Ieda, Junichi
Journal of the Physical Society of Japan, 92(7), p.074705_1 - 074705_9, 2023/06
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Topological electromagnetism owing to nontrivial momentum-space topology of electrons in insulators gives rise to diverse anomalous magnetoelectric responses. While conventional inductors and capacitors are based on classical electromagnetism described by Maxwell's equations, here we show that topological electromagnetism in combination with spin dynamics in magnets also generates an inductance or a capacitance. We build a generic framework to extract the complex impedance on the basis of topological field theory, and demonstrate the emergence of an inductance or a capacitance in several heterostructure setups. In comparison with the previously-studied emergent inductances in metallic magnets, insulators highly suppress the power loss, because of the absence of Joule heating. We show that the inductance from topological electromagnetism is achieved at low current and high frequency, and is also advantageous in its power efficiency, as characterized by the high quality factor (Q-factor).
Nakayama, Katsumasa*; Suzuki, Kei
Proceedings of Science (Internet), 430, p.379_1 - 379_9, 2023/04
The conventional Casimir effect has been studied in the continuous spacetime, but to elucidate its counterpart in the lattice space is an important subject. Here, we discuss various types of Casimir effects for quantum fields on the lattice. By using a definition of the Casimir energy on the lattice, we show that the Casimir effect for the Wilson fermion is similar to that for the continuous Dirac fermion. We apply our definition to an effective Hamiltonian describing Dirac semimetals, such as Cd
As
and NaBi, and find an oscillatory behavior of the Casimir energy as a function of film thickness of semimetals. We also study contributions from Landau levels under magnetic fields and the Casimir effect for nonrelativistic particle fields on the lattice.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physical Review D, 104(9), p.094515_1 - 094515_11, 2021/11
Times Cited Count：4 Percentile：37.94(Astronomy & Astrophysics)We investigate the Kondo effect with Wilson fermions. This is based on a mean-field approach for the chiral Gross-Neveu model including four-point interactions between a light Wilson fermion and a heavy fermion. For massless Wilson fermions, we demonstrate the appearance of the Kondo effect. We point out that there is a coexistence phase with both the light-fermion scalar condensate and Kondo condensate, and the critical chemical potentials of the scalar condensate are shifted by the Kondo effect. For negative-mass Wilson fermions, we find that the Kondo effect is favored near the parameter region realizing the Aoki phase. Our findings will be useful for understanding the roles of heavy impurities in Dirac semimetals, topological insulators, and lattice simulations.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physical Review Research (Internet), 3(2), p.023201_1 - 023201_23, 2021/06
The Casimir effect arises from the zero-point energy of particles in momentum space deformed by the existence of two parallel plates. For degrees of freedom on the lattice, its energy-momentum dispersion is determined so as to keep a periodicity within the Brillouin zone, so that its Casimir effect is modified. We study the properties of Casimir effect for lattice fermions, such as the naive fermion, Wilson fermion, and overlap fermion based on the M
bius domain-wall fermion formulation, in the 
, 
, and 
dimensional spacetime with the periodic or antiperiodic boundary condition. An oscillatory behavior of Casimir energy between odd and even lattice size is induced by the contribution of ultraviolet-momentum (doubler) modes, which realizes in the naive fermion, Wilson fermion in a negative mass, and overlap fermions with a large domain-wall height. Our findings can be experimentally observed in condensed matter systems such as topological insulators and also numerically measured in lattice simulations.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
Physics Letters B, 809, p.135713_1 - 135713_7, 2020/10
Times Cited Count：10 Percentile：76.76(Astronomy & Astrophysics)We propose a definition of the Casimir energy for free lattice fermions. From this definition, we study the Casimir effects for the massless or massive naive fermion, Wilson fermion, and (Mbius) domain-wall fermion in 1+1 dimensional spacetime with the spatial periodic or antiperiodic boundary condition. For the naive fermion, we find an oscillatory behavior of the Casimir energy, which is caused by the difference between odd and even lattice sizes. For the Wilson fermion, in the small lattice size of 
, the Casimir energy agrees very well with that of the continuum theory, which suggests that we can control the discretization artifacts for the Casimir effect measured in lattice simulations. We also investigate the dependence on the parameters tunable in Mbius domain-wall fermions. Our findings will be observed both in condensed matter systems and in lattice simulations with a small size.
Te
Shikin, A. M.*; Estyunin, D. A.*; Klimovskikh, I. I.*; Filnov, S. O.*; Kumar, S.*; Schwier, E. F.*; Miyamoto, Koji*; Okuda, Taichi*; Kimura, Akio*; Kuroda, Kenta*; et al.
Scientific Reports (Internet), 10, p.13226_1 - 13226_13, 2020/08
Times Cited Count：59 Percentile：96.43(Multidisciplinary Sciences)Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
Physical Review Research (Internet), 2(2), p.023195_1 - 023195_11, 2020/05
V
Te
Sumida, Kazuki*; Kakoki, Masaaki*; Reimann, J.*; Nurmamat, M.*; Goto, Shinichi*; Takeda, Yukiharu; Saito, Yuji; Kokh, K. A.*; Tereshchenko, O. E.*; G
dde, J.*; et al.
New Journal of Physics (Internet), 21(9), p.093006_1 - 093006_8, 2019/09
Times Cited Count：11 Percentile：65.02(Physics, Multidisciplinary)
(Sb
Bi)
TeYe, M.*; Xu, T.*; Li, G.*; Qiao, S.*; Takeda, Yukiharu; Saito, Yuji; Zhu, S.-Y.*; Nurmamat, M.*; Sumida, Kazuki*; Ishida, Yukiaki*; et al.
Physical Review B, 99(14), p.144413_1 - 144413_7, 2019/04
Times Cited Count：12 Percentile：56.27(Materials Science, Multidisciplinary)Shikin, A. M.*; Estyunin, D. A.*; Surnin, Yu. I.*; Koroleva, A. V.*; Shevchenko, E. V.*; Kokh, K. A.*; Tereshchenko, O. E.*; Kumar, S.*; Schwier, E. F.*; Shimada, Kenya*; et al.
Scientific Reports (Internet), 9(1), p.4813_1 - 4813_17, 2019/03
Times Cited Count：19 Percentile：71.48(Multidisciplinary Sciences)TeYe, M.*; Li, W.*; Zhu, S.-Y.*; Takeda, Yukiharu; Saito, Yuji; Wang, J.*; Pan, H.*; Nurmamat, M.*; Sumida, Kazuki*; Ji, F.*; et al.
Nature Communications (Internet), 6, p.8913_1 - 8913_7, 2015/11
Times Cited Count：52 Percentile：89.95(Multidisciplinary Sciences)Magnetically doped topological insulators are predicted to exhibit exotic phenomena including the quantized anomalous Hall effect and a dissipationless transport, which facilitate the development of low-power-consumption devices using electron spins. The realization of the quantized anomalous Hall effect is so far restricted to the Cr-doped (Sb,Bi)Te system at extremely low temperature; however, the microscopic origin of its ferromagnetism is poorly understood. Here we present an element-resolved study for Cr-doped (Sb,Bi)Te using X-ray magnetic circular dichroism to unambiguously show that the long-range magnetic order is mediated by the p-hole carriers of the host lattice, and the interaction between the Sb(Te) p and Cr d states is crucial.
Kawasuso, Atsuo; Li, H.; Maekawa, Masaki; Abe, Hiroshi; Miyashita, Atsumi
no journal, ,
no abstracts in English
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Araki, Yasufumi; Misawa, Takahiro*; Nomura, Kentaro*
no journal, ,
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
no journal, ,
We propose a definition of the Casimir energy for free lattice fermions. From this definition, we study the Casimir effects for the massless or massive naive fermion, Wilson fermion, and (Mbius) domain-wall fermion in dimensional spacetime with the spatial periodic or antiperiodic boundary condition. For the naive fermion, we find an oscillatory behavior of the Casimir energy, which is caused by the difference between odd and even lattice sizes. For the Wilson fermion, in the small lattice size of , the Casimir energy agrees very well with that of the continuum theory, which suggests that we can control the discretization artifacts for the Casimir effect measured in lattice simulations. We also investigate the dependence on the parameters tunable in Mbius domain-wall fermions. Our findings will be observed both in condensed matter systems and in lattice simulations with a small size.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
no journal, ,
no abstracts in English
Araki, Yasufumi; Ieda, Junichi
no journal, ,
Araki, Yasufumi; Ieda, Junichi
no journal, ,
Sugimoto, Satoshi*; Araki, Yasufumi; Takahashi, Yukiko*; Ieda, Junichi; Kasai, Shinya*
no journal, ,
no abstracts in English
