Article
Materials Science, Multidisciplinary
A. S. Shankar, D. O. Oriekhov, Andrew K. Mitchell, L. Fritz
Summary: The emergence of flat bands in twisted bilayer graphene at the magic angle can be understood as a result of vanishing Fermi velocity of the Dirac cone and higher-order van Hove singularities. These characteristics play an important role in exotic phenomena observed in this material, such as superconductivity and magnetism, by enhancing electronic correlation effects. One of these correlation effects is the Kondo effect due to a magnetic impurity embedded in twisted bilayer graphene. The interplay between Dirac, van Hove, and Kondo physics leads to nontrivial behavior at finite temperatures relevant to experiments.
Article
Materials Science, Multidisciplinary
Yin-Zou Zhao, Qi-Yi Wu, Chen Zhang, Bo Chen, Wei Xia, Jiao-Jiao Song, Ya-Hua Yuan, Hao Liu, Fan-Ying Wu, Xue-Qing Ye, Hong-Yi Zhang, Han Huang, Hai-Yun Liu, Yu-Xia Duan, Yan-Feng Guo, Jun He, Jian-Qiao Meng
Summary: Ultrafast optical spectroscopy was used to investigate the ultrafast quasiparticle dynamics of antiferromagnetic Kondo lattice CeAuSb2 as a function of temperature and fluence. Our results reveal the behavior of quasiparticles at different temperatures and light intensities, including the opening of a hybridization gap, the coupling of coherent phonon modes with Kondo effect and magnetic orders, and a possible photoinduced nonthermal phase transition. These observations shed light on the hybridization dynamics and magnetic orders in heavy fermion systems.
Article
Physics, Multidisciplinary
Guangjie Li, Yuval Oreg, Jukka I. Vaeyrynen
Summary: A Coulomb blockaded M-Majorana island coupled to normal metal leads realizes a novel type of Kondo effect where the effective impurity spin transforms under the orthogonal group SO(M). The impurity spin stems from the nonlocal topological ground state degeneracy of the island and thus the effect is known as the topological Kondo effect. We introduce a physically motivated N-channel generalization of the topological Kondo model.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Multidisciplinary
Jiangfan Wang, Yi-Feng Yang
Summary: Magnetic frustrations can enhance quantum fluctuations and lead to exotic topological insulating states in spin systems. When coupled to mobile electrons, they may give rise to unusual non-Fermi liquid or metallic spin liquid states whose nature has not been well explored. By considering a spin current Kondo mechanism in a frustrated Kondo model, a series of non-Fermi liquid phases can be formed.
SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY
(2022)
Article
Materials Science, Multidisciplinary
Damian Tomaszewski, Piotr Busz, Jan Martinek
Summary: This paper provides a detailed theoretical description of the influence of spin accumulation in metallic Fermi leads on the Kondo effect in systems such as quantum dots and Kondo alloys. The study shows that the presence of spin accumulation, magnetic field, and ferromagnetic leads spin polarization can suppress the Kondo effect, but for appropriately selected parameter values, these effects can compensate each other and may lead to the restoration of the Kondo effect in the analyzed systems. The paper also discusses recent experiments related to spin current in Kondo alloys.
Article
Materials Science, Multidisciplinary
Baohua Wang, Yangqing Wu, Haoming Wei, Xin Chen, Xiubing Zhang, Bingqiang Cao
Summary: In this work, high-quality LaAlO3/SrTiO3 heterostructures were prepared under different oxygen partial pressure, and the role of oxygen vacancy in the Kondo effect at LaAlO3/SrTiO3 interface was investigated. It was found that the formation of Ti3+ local moments related to oxygen vacancy can be controlled by oxygen partial pressure, resulting in a change in Kondo temperature. This work paves the way for studying the two-dimensional electron gas at the oxide interface.
Article
Materials Science, Multidisciplinary
Guangjie Li, Elio J. Koenig, Jukka I. Vayrynen
Summary: This study proposes a mesoscopic setup for the Kondo effect that can produce emergent anyons, including Majorana fermions, Fibonacci anyons, and Z3 parafermions, even without perfect channel symmetry. The model is mapped to the multichannel Kondo effect associated with an internal SU(2) symmetry, and the scaling of various observables, including conductance, is predicted using conformal field theory. This work not only provides a platform for robust Kondo-based anyons, but also sheds light on the physics of strongly correlated materials with competing order parameters.
Article
Astronomy & Astrophysics
Tsutomu Ishikawa, Katsumasa Nakayama, Kei Suzuki
Summary: The study demonstrates the appearance of the Kondo effect for massless Wilson fermions and a coexistence phase with both the light-fermion scalar condensate and Kondo condensate. For negative-mass Wilson fermions, the Kondo effect is favored near the parameter region realizing the Aoki phase.
Article
Materials Science, Multidisciplinary
Fatemeh Mohammadi, Amirhossein Saedpanah, Abolhassan Vaezi, Mehdi Kargarian
Summary: In this work, we study a superconducting Kondo lattice model to explore the interplay between electron correlations and conduction electrons. We obtain the phase diagram of the model and identify a topological order phase and a Kondo compensated phase. Numerical calculations show that the topological order is a stable phase.
Article
Materials Science, Multidisciplinary
Peng Li, Huiqing Ye, Yong Hu, Yuan Fang, Zhiguang Xiao, Zhongzheng Wu, Zhaoyang Shan, Ravi P. Singh, Geetha Balakrishnan, Dawei Shen, Yi-feng Yang, Chao Cao, Nicholas C. Plumb, Michael Smidman, Ming Shi, Johann Kroha, Huiqiu Yuan, Frank Steglich, Yang Liu
Summary: In this study, direct spectroscopic evidence for the competition between magnetic order and the Kondo effect in a Kondo lattice system is found through high-resolution photoemission spectroscopy.
Article
Chemistry, Multidisciplinary
Mengting Zhao, Bin-Bin Chen, Yilian Xi, Yanyan Zhao, Hang Xu, Hongrun Zhang, Ningyan Cheng, Haifeng Feng, Jincheng Zhuang, Feng Pan, Xun Xu, Weichang Hao, Wei Li, Si Zhou, Shi Xue Dou, Yi Du
Summary: An anomalous enhancement of Kondo screening is observed in the recently discovered 3d-HF system Fe3GeTe2, where a itinerant Kondo-Ising model is established to explain the phenomenon, providing insight into the competition between Ising ferromagnetism and Kondo screening. This work sheds light on the microscopic origin of d-electron HF states in Fe3GeTe2 and inspires further studies on quantum many-body effects with Kondo holes.
Article
Materials Science, Multidisciplinary
Jian-Jun Dong, Yi-feng Yang
Summary: This study introduces a concept of hybridization bond phase to address the emergence and development of heavy electrons on the Kondo lattice, proposing a scenario based on phase correlation. The research reveals that the correlation length of Kondo hybridizations grows logarithmically with lowering temperature and leads to the formation of the Kondo insulating state at low temperatures.
Article
Physics, Condensed Matter
Chang-Jong Kang, Kyoo Kim, B. Min
Summary: First-principles band structure theory based on density functional theory (DFT) is essential for studying the topological properties of weakly-correlated systems. However, its application is limited in strongly-correlated f-electron systems. In this perspective, the band theoretical approaches to topological properties of strongly-correlated f-electron Kondo systems are examined. The current understanding of electronic structures and topological properties of strongly-correlated 4f-electron systems and a 5f-electron system is summarized, and future directions for improving theoretical band approaches to search for new topological f-electron systems are provided.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
Article
Multidisciplinary Sciences
Sami Dzsaber, Xinlin Yan, Mathieu Taupin, Gaku Eguchi, Andrey Prokofiev, Toni Shiroka, Peter Blaha, Oleg Rubel, Sarah E. Grefe, Hsin-Hua Lai, Qimiao Si, Silke Paschen
Summary: The discovery of a giant spontaneous Hall effect in the Kondo semimetal Ce3Bi4Pd3, attributed to Weyl nodes emerging due to the Kondo interaction, showcases an extreme topological response. This phenomenon differs from previously detected anomalous Hall effect in materials with broken time-reversal symmetry, and requires a beyond-perturbation-theory description.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Multidisciplinary Sciences
Annika Kurzmann, Yaakov Kleeorin, Chuyao Tong, Rebekka Garreis, Angelika Knothe, Marius Eich, Christopher Mittag, Carolin Gold, Folkert Kornelis de Vries, Kenji Watanabe, Takashi Taniguchi, Vladimir Fal'ko, Yigal Meir, Thomas Ihn, Klaus Ensslin
Summary: The study explores the interplay between spin-orbit interaction and the Kondo effect, revealing the possibility of underscreened Kondo effects in bilayer graphene quantum dots. Unlike carbon nanotubes, a different experimental platform is employed to investigate Kondo physics in a planar carbon material.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Tetsuro Kusamoto, Chie Ohde, Shiori Sugiura, Satoshi Yamashita, Ryota Matsuoka, Taichi Terashima, Yasuhiro Nakazawa, Hiroshi Nishihara, Shinya Uji
Summary: In this study, a newly synthesized organic quantum spin liquid (QSL) was investigated for its structure and physical properties. The antiferromagnetic interaction in this QSL was found to be smaller than that in other organic QSLs, while the chi(0) and gamma values were larger. The results provide evidence of the spinon Fermi surface in the QSLs.
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN
(2022)
Article
Physics, Multidisciplinary
Takako Konoike, Taichi Terashima, Shinya Uji, Yuya Hattori, Reizo Kato
Summary: In this study, magnetic torque measurements were used to investigate the magnetic properties of the organic conductors alpha-(BETS)(2)I-3 and alpha-(BEDT-TTF)(2)I-3. The magnetic torque reflecting anisotropic diamagnetism was observed in alpha-(BEDT-TTF)(2)I-3, while complex torque curves in alpha-(BETS)(2)I-3 provided the first evidence for the existence of magnetic order. The observed change in torque amplitude at the metal-insulator crossover temperature suggests a relationship between this crossover and the magnetic nature of alpha-(BETS)(2)I-3.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Materials Science, Multidisciplinary
Taichi Terashima, Shinya Uji, Teng Wang, Gang Mu
Summary: This study reports the phenomenon that the quantum-oscillation frequencies exhibit a negative shift, which can be utilized to identify Dirac/Weyl fermions, but there is a deviation between experimental results and theoretical predictions at lower temperatures.
NPJ QUANTUM MATERIALS
(2022)
Article
Physics, Multidisciplinary
Shinya Uji, Taichi Terashima, Daigorou Hirai, Takahito Anbai, Zenji Hiroi
Summary: Magnetic torque measurements were conducted to investigate the electronic state of metallic beta-phase ReO2 with Dirac nodal lines forming a loop chain. The experimental results showed sinusoidal torque curves with a two-fold symmetry throughout the entire temperature range. As the temperature decreased, a significant nonlinear magnetization effect was observed, especially for the magnetic field in the ac plane. Analysis based on Landau theory revealed that this change in torque signal was attributed to electric quadrupole fluctuations. Furthermore, the study found a strongly enhanced anisotropic susceptibility due to quadrupole fluctuations near 0K and 0T, suggesting the presence of quantum critical behavior.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Chemistry, Inorganic & Nuclear
Naoki Kikugawa, Taichi Terashima, Takashi Kato, Momoko Hayashi, Hitoshi Yamaguchi, Shinya Uji
Summary: In this study, single crystals of a magnetic Weyl semimetal candidate NdAlGe were successfully grown using a floating-zone technique with laser diodes as the heat source. The crystals showed magnetic order at 13.5 K and were characterized for their physical properties using various measurements. The study revealed the anisotropic magnetoelasticity, magneto-entropy, and charge transport induced by the magnetic order in NdAlGe.
Article
Physics, Condensed Matter
Daigorou Hirai, Takahito Anbai, Takako Konoike, Shinya Uji, Yuya Hattori, Taichi Terashima, Hajime Ishikawa, Koichi Kindo, Naoyuki Katayama, Tamio Oguchi, Zenji Hiroi
Summary: Quantum oscillations were measured in the magnetic torque and electrical resistivity of ss-ReO2 to examine its electronic structure. The observed de Haas-van Alphen oscillation branches were consistent with first-principles calculations that predicted the presence of four Fermi surfaces. The small-electron Fermi surface exhibited a very small cyclotron mass, only 0.059 times that of free electrons, which suggests a linear dispersion of the energy band. These findings support the existence of the predicted hourglass nodal chain in ss-ReO2 near the Fermi energy.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Materials Science, Multidisciplinary
Taichi Terashima, Hishiro T. Hirose, Naoki Kikugawa, Shinya Uji, David Graf, Hitoshi Sugawara
Summary: This paper investigates a material composed of CeFe2Al10, which exhibits metallic conduction despite an increase in resistivity with decreasing temperature below 20K.
Article
Materials Science, Multidisciplinary
Yuya Hattori, Shunsuke Yoshizawa, Keisuke Sagisaka, Yuki Tokumoto, Keiichi Edagawa, Takako Konoike, Shinya Uji, Taichi Terashima
Summary: Scanning tunneling microscopy and transport measurements were used to investigate the electronic structure and temperature dependence in heavily Sr and Na codoped PbTe. The band gap increases with doping, leading to band convergence, which is desirable for thermoelectric materials. At higher temperatures, carrier redistribution occurs between different bands.
Article
Materials Science, Multidisciplinary
Hiroaki Hayashi, Yuichi Shirako, Lei Xing, Alexei A. Belik, Masao Arai, Masanori Kohno, Taichi Terashima, Hiroshi Kojitani, Masaki Akaogi, Kazunari Yamaura
Summary: In this study, the anomalous Hall effect in the cubic kagome antiferromagnet Mn3Sb is successfully measured, validating its theoretical predictions. These findings contribute to a comprehensive understanding of the anomalous Hall effect in noncollinear antiferromagnetic materials.
Article
Materials Science, Multidisciplinary
Taichi Terashima, Hishiro T. Hirose, Yoshitaka Matsushita, Shinya Uji, Hiroaki Ikeda, Yuki Fuseya, Teng Wang, Gang Mu
Summary: In this study, the electronic anisotropy of CaFeAsF was investigated by measuring its resistivity under magnetic fields with varying field directions. The results reveal the presence of electron anisotropy in iron-based compounds and provide insights into the nematic electronic state in various materials.
Article
Materials Science, Multidisciplinary
Natalia Drichko, Shiori Sugiura, Minoru Yamashita, Akira Ueda, Shinya Uji, Nora Hassan, Yoshiya Sunairi, Hatsumi Mori, Elena Zhilyaeva, Svetlana Torunova, Rimma N. Lyubovskaya
Summary: This study discusses the coupling of charge and spin degrees of freedom in a material based on the BEDT-TTF molecule through magnetic property measurements at different temperatures. The observed charge and spin separation below 30 K and coupling below 24 K are significant for understanding the properties of quasi-two-dimensional Mott insulators.
Article
Materials Science, Multidisciplinary
Shinya Uji, Takako Konoike, Yuya Hattori, Taichi Terashima, Tamio Oguchi, Takahiro Yamada, Daigorou Hirai, Zenji Hiroi
Summary: Quantum oscillations in magnetic torque have been measured to investigate the Fermi surface of the topological nodal-line semimetal NaAlSi with a superconducting transition. The results show the presence of small Fermi surfaces elongated in the kz direction and four oscillation branches. Large mass enhancement factors have been obtained, likely associated with superconductivity.
Article
Materials Science, Multidisciplinary
Hishiro T. Hirose, Taichi Terashima, Daigorou Hirai, Yasuhito Matsubayashi, Naoki Kikugawa, David Graf, Kaori Sugii, Shiori Sugiura, Zenji Hiroi, Shinya Uji
Summary: Pyrochlore oxide Cd2Re2O7 undergoes structural transitions upon cooling, breaking its inversion symmetry. The electronic structure of the lowest temperature phase of Cd2Re2O7 is determined using quantum oscillation measurements and electronic structure calculations, revealing the strong influence of antisymmetric spin-orbit interaction. The microscopic picture of the metallic electric-toroidal-quadrupole order is visualized, providing insight into the unconventional phenomena in this order.