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Hattori, Koichi*; Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*
Physical Review B, 108(24), p.245110_1 - 245110_11, 2023/12
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We develop a mean-field theory of a novel Kondo effect emerging in systems without a Fermi surface, which instead emerges under strong magnetic fields. We determine the magnitude of the Kondo condensate, which is a particle pairing composed of conducting Dirac fermions and localized impurities. We focus on the competition between the Kondo effect and the energy gap formation that stems from the pairing among the Dirac fermions leading to the dynamical chiral symmetry breaking. We find that this competition induces a quantum critical point. We also investigate finite-temperature effects. This system at vanishing fermion density can be studied with Monte Carlo lattice simulations, which do not suffer from the sign problem.
Hattori, Koichi*; Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*
EPJ Web of Conferences, 276, p.01015_1 - 01015_5, 2023/03
Times Cited Count：0 Percentile：0.91(Physics, Atomic, Molecular & Chemical)We investigate the QCD phase diagram in strong magnetic fields with heavy-quark impurities and determine the ground state within the mean-field analysis. The ground state is characterized by magnitudes of the pairing not only between the light quark and antiquark, i.e., chiral condensate, but also between the light quark and heavy-quark impurity, dubbed the Kondo condensate. We propose signatures of the interplay and/or competition between those two pairing phenomena reflected in the magnitude of the chiral condensate that is saturated with respect to the magnetic-field strength and anomalously increases with increasing temperature.
RhGa explored by 
Ga nuclear quadrupole resonanceYamamoto, Shingo*; Fujii, Takuto*; Luther, S.*; Yasuoka, Hiroshi*; Sakai, Hironori; B
rtl, F.*; Ranjith, K. M.*; Rosner, H.*; Wosnitza, J.*; Strydom, A. M.*; et al.
Physical Review B, 106(11), p.115125_1 - 115125_5, 2022/09
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We have studied the microscopic magnetic properties, the nature of the 130 K phase transition, and the ground state in the recently synthesized compound CeRhGa by use of Ga nuclear quadrupole resonance (NQR). The NQR spectra clearly show an unusual phase transition at 
K, yielding a splitting of the high-temperature single NQR line into two well-resolved NQR lines, providing evidence for two crystallographically inequivalent Ga sites. The NQR frequencies are in good agreement with fully relativistic calculations of the band structure. Our NQR results indicate the absence of magnetic or charge order down to 0.3 K. The temperature dependence of the spin-lattice relaxation rate 
shows three distinct regimes, with onset temperatures at 
and 2 K. The temperature-independent , observed between and 2 K, crosses over to a Korringa process, 
, below 
2 K, which evidences a rare two-ion Kondo scenario: The system evolves into a dense Kondo coherent state below 2.0 and 0.8 K probed by the two different Ga sites.
Suenaga, Daiki*; Araki, Yasufumi; Suzuki, Kei; Yasui, Shigehiro*
Physical Review D, 105(7), p.074028_1 - 074028_19, 2022/04
Times Cited Count：2 Percentile：36.77(Astronomy & Astrophysics)We propose a new mechanism of the heavy-quark spin polarization (HQSP) in quark matter induced by the Kondo effect under an external magnetic field. The Kondo effect is caused by a condensate between a heavy and a light quark called the Kondo condensate leading to a mixing of the heavy- and light-quark spins. Thus, the HQSP is driven through the Kondo effect from light quarks coupling with the magnetic field in quark matter. For demonstration, we employ the Nambu-Jona-Lasinio type model under a magnetic field and investigate the HQSP within the linear response theory with vertex corrections required by the 
electromagnetic gauge invariance. As a result, we find that the HQSP arises significantly with the appearance of the Kondo effect. Our findings are testable in future sign-problem-free lattice simulations.
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.
Yamamoto, Tsuyoshi*; Kato, Takeo*; Matsuo, Mamoru
Physical Review B, 104(12), p.L121401_1 - L121401_5, 2021/09
Times Cited Count：5 Percentile：44.86(Materials Science, Multidisciplinary)Suenaga, Daiki*; Araki, Yasufumi; Suzuki, Kei; Yasui, Shigehiro*
Physical Review D, 103(5), p.054041_1 - 054041_17, 2021/03
Times Cited Count：5 Percentile：45.23(Astronomy & Astrophysics)We investigate the influence of the Kondo effect, namely, the nonperturbative effect induced by heavy impurities, on the chiral separation effect (CSE) in quark matter. We employ a simple effective model incorporating the Kondo condensate made of a light quark and a heavy quark, and compute the response function of the axial current to the magnetic field in the static and dynamical limits. As a result, we find that the Kondo effect catalyzes the CSE in both of the limits, and in particular the CSE in the dynamical limit can be enhanced by a factor of approximately 3. Our findings clearly show that the presence of heavy impurities in quark matter can play an important role in the transport phenomena of light quarks induced by a magnetic field.
Araki, Yasufumi; Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*
Physical Review Research (Internet), 3(1), p.013233_1 - 013233_12, 2021/03
We investigate two different types of relativistic Kondo effects, distinguished by heavy-impurity degrees of freedom, by focusing on the energy-momentum dispersion relations of the ground state with condensates composed of a light Dirac fermion and a nonrelativistic impurity fermion. Heavy fermion degrees of freedom are introduced in terms of two types of heavy-fermion effective theories, in other words, two heavy-fermion limits for the heavy Dirac fermion, which is known as the heavy-quark effective theories (HQETs) in high-energy physics. While the first one includes only the heavy-particle component, the second one contains both the heavy-particle and heavy-antiparticle components, which are opposite in their parity. From these theories, we obtain two types of Kondo effects, in which the dispersions near the Fermi surface are very similar, but they differ in the structure at low momentum. We also classify the possible forms of condensates in the two limits. The two Kondo effects will be examined by experiments with Dirac/Weyl semimetals or quark matter, lattice simulations, and cold-atom simulations.
Sb
uncovered by soft X-ray magnetic circular dichroismSaito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.
Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10
Times Cited Count：1 Percentile：6.04(Materials Science, Multidisciplinary)Suenaga, Daiki*; Suzuki, Kei; Araki, Yasufumi; Yasui, Shigehiro*
Physical Review Research (Internet), 2(2), p.023312_1 - 023312_13, 2020/06
The Kondo effect is induced by the interaction between light fermions near the Fermi surface and heavy impurities, and it affects electric/thermal/transport properties of matter. The chirality (right-handed or left-handed) is one of the unique properties of relativistic (Dirac or Weyl) fermions. In normal matter, the numbers of right- and left-handed particles are equivalent to each other, but environments with a chirality imbalance can also be realized. In this paper, we theoretically propose the Kondo effect driven by a chirality imbalance (or chiral chemical potential) of relativistic light fermions. This effect is caused by the mixing between a right-handed (or left-handed) fermion and a heavy impurity in the chirality imbalanced matter. This is different from the usual Kondo effect induced by finite density (or chemical potential) for light fermions. We construct an effective model with an interaction between a relativistic fermion and a heavy impurity, and we derive the realization of the Kondo effect from both a perturbative calculation and a nonperturbative mean-field approach. We also discuss the temperature dependence, the coupling constant dependence, the susceptibilities, and the order of the phase transition for the Kondo effect. Such a Kondo effect will be tested by future lattice simulations.
Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*
Physical Review Research (Internet), 2(2), p.023066_1 - 023066_11, 2020/04
The QCD Kondo effect is a quantum phenomenon in which heavy (charm or bottom) quarks exist as impurity particles in quark matter composed of light quarks at extremely high density. In this paper, we theoretically predict the existence of the exciton modes above the ground state of the quark matter governed by the QCD Kondo effect. We construct an effective model based on the mean field approximation and investigate possible quantum numbers (such as spin and parity) of excitons and their dispersion relations. These excitons can be electrically (color) neutral, so that they are observed as the neutral currents in transport phenomena. As a result, they contribute to violation of the Wiedemann-Franz law for the electric (color) and heat conductivities. Such Kondo excitons are an universal phenomenon for relativistic (Dirac or Weyl) fermions, and the same concept will also be applied to Dirac or Weyl electron systems.
electron state in the heavy fermion superconductor NpPd
AlMetoki, Naoto; Aoki, Dai*; Griveau, J.-C.*; Otsuki, Junya*
Journal of the Physical Society of Japan, 89(2), p.024707_1 - 024707_6, 2020/02
Times Cited Count：3 Percentile：31.18(Physics, Multidisciplinary)The pseudo triplet ground state in the heavy-fermion superconductor NpPdAl was concluded. The magnetic susceptibility 
can be reproduced by the singlet ground state 
with the main component of 
and the first excited doublet 
dominated by 
at 
,K. The magnetization curve can be explained from the effective local hamiltonian for pseudo spin 
=1 with 
(
) equivalent to the quadrupole operator 
. The specific heat can be described with the Kondo model normalized to give the entropy R
, corresponding to the pseudo triplet state. The derived Kondo temperature 
,K comparable to the level splitting ,K indicates the contribution of the excited doublet to the possible multi-channel Kondo effect.
Hotta, Takashi
Physical Review Letters, 96(19), p.197201_1 - 197201_4, 2006/05
Times Cited Count：40 Percentile：81.37(Physics, Multidisciplinary)A mechanism of non-magnetic Kondo effect is proposed on the basis of a multiorbital Anderson model coupled with dynamical Jahn-Teller (JT) phonons. An electron system coupled dynamically with JT phonons has a vibronic ground state with double degeneracy due to clockwise and anti-clockwise rotational modes with entropy of 
. When a temperature is lower than a characteristic energy to turn the rotational direction, the rotational degree of freedom is eventually suppressed and the corresponding entropy is released, leading to quasi-Kondo behavior. We discuss possible relevance of this quasi-Kondo phenomenon to electronic properties of filled skutterudites.
Ag
Okane, Tetsuo; Fujimori, Shinichi; Mamiya, Kazutoshi; Okamoto, Jun; Fujimori, Atsushi; Tsujii, Naoto*; Yoshimura, Kazuyoshi*
Acta Physica Polonica B, 34(2), p.1019 - 1022, 2003/02
no abstracts in English
Miyahara, Tsuneaki*; Ishii, Hiroyoshi*; Takayama, Yasuhiro*; Hirose, Masaaki*; Maruyama, Kenichi*; Obu, Kenji*; Shinoda, Motoki*; Muro, Takayuki*; Saito, Yuji; Matsuda, Tatsuma*; et al.
Journal of the Physical Society of Japan, 70(10), p.2977 - 2981, 2001/10
Times Cited Count：6 Percentile：42.11(Physics, Multidisciplinary)no abstracts in English
Haga, Yoshinori
Mombusho Kagaku Kenkyuhi Juten Ryoiki Kenkyu "Kyosokan Dendokei No Butsuri" Nyusu Reta, 3(2), 56 Pages, 1995/09
no abstracts in English
Suzuki, Kei
no journal, ,
The Kondo effect is a well-known phenomenon in metal including localized impurities, which leads to drastic modification of electric/thermal/transportproperties of metal. In high-density quark matter, a similar effect can be induced by interaction between a light quark and a "colored" impurity like heavy quarks, which is the so-called QCD Kondo effect. In this talk, I will review a novel phase with condensates consisting of a light quark and a heavy quark, that is the Kondo phase predicted in Refs.[1,2]. In particular, recently, we found that several exciton modes can be excited in this phase, by using an improved analysis [3]. Such modes could affect the transport properties of high-density quark matter. [1] S. Yasui, K. Suzuki, and K. Itakura, Nucl. Phys. A983 (2019) 90. [2] S. Yasui, K. Suzuki, and K. Itakura, Phys. Rev. D96 (2017) 014016. [3] D. Suenaga, K. Suzuki, and S. Yasui, arXiv:1909.07573.
Ishikawa, Tsutomu*; Nakayama, Katsumasa*; Suzuki, Kei
no journal, ,
no abstracts in English
Hattori, Koichi*; Suenaga, Daiki*; Suzuki, Kei; Yasui, Shigehiro*
no journal, ,
no abstracts in English
Zn
Kitazawa, Takafumi; Ikeda, Yoichi*; Imajo, Shusaku*; Haga, Yoshinori; Kohama, Yoshimitsu*; Tokunaga, Yo; Fujita, Masaki*
no journal, ,
no abstracts in English
