Article
Physics, Multidisciplinary
M. Mogi, Y. Okamura, M. Kawamura, R. Yoshimi, K. Yasuda, A. Tsukazaki, K. S. Takahashi, T. Morimoto, N. Nagaosa, M. Kawasaki, Y. Takahashi, Y. Tokura
Summary: In this study, the half-integer quantization of Hall conductance was observed in a synthetic heterostructure called a semi-magnetic topological insulator. The results provide evidence of the condensed matter realization of the parity anomaly and offer a new way to study the physics enabled by a single Dirac fermion.
Article
Chemistry, Physical
Wenbin Wu, Zeping Shi, Yuhan Du, Yuxiang Wang, Fang Qin, Xianghao Meng, Binglin Liu, Yuanji Ma, Zhongbo Yan, Mykhaylo Ozerov, Cheng Zhang, Hai-Zhou Lu, Junhao Chu, Xiang Yuan
Summary: The manuscript reports experimental observations of a Lifshitz transition in a topological insulator HfTe5 under a strong magnetic field, leading to the formation of one-dimensional Weyl modes in a three-dimensional material. By tracking the Landau level transitions, the study demonstrates that band inversion drives the crossing of zeroth Landau bands and the formation of a one-dimensional Weyl mode. This transition occurs at 21 T and moves the Weyl mode close to the Fermi level.
Article
Nanoscience & Nanotechnology
Pan He, Gavin Kok Wai Koon, Hiroki Isobe, Jun You Tan, Junxiong Hu, Antonio H. Castro Neto, Liang Fu, Hyunsoo Yang
Summary: Graphene moire superlattices exhibit giant second-order nonlinear transports, both longitudinal and transverse, under zero magnetic field, originating from the skew scattering of chiral Bloch electrons. These findings provide an alternative means for inducing second-order transports in van der Waals heterostructures.
NATURE NANOTECHNOLOGY
(2022)
Article
Physics, Multidisciplinary
Jaksa Vucicevic, Rok Zitko
Summary: By using dynamical mean field theory, the magnetic field dependence of dc conductivity in the Hubbard model on the square lattice was investigated, revealing novel oscillatory effects at elevated temperature which are in line with recent experiments on graphene superlattices. The study elucidated the key roles of off-diagonal elements of the current vertex and the incoherence of electronic states in explaining trends with respect to temperature and doping.
PHYSICAL REVIEW LETTERS
(2021)
Editorial Material
Chemistry, Physical
Zhengguang Lu, Long Ju
Summary: Scientists have achieved Weyl modes by subjecting a topological insulator to strong magnetic fields, which enhances the capability to design, engineer, and manipulate topological materials, with significant implications for physics research and material applications.
Article
Materials Science, Multidisciplinary
Chuanchang Zeng, Snehasish Nandy, Pu Liu, Sumanta Tewari, Yugui Yao
Summary: In this study, we investigated the nonlinear planar effects in Weyl semimetals from the semiclassical regime to the ultraquantum limit using Boltzmann transport theory incorporating Landau quantization. Our results suggest that the quantum oscillations in the nonlinear planar effects can serve as a robust signature of the chiral anomaly in Weyl semimetals. By obtaining analytical expressions, we demonstrated that the quantum oscillations in the nonlinear regime exhibit two different periods compared to the linear response regime. Furthermore, the characteristic angular dependence of the chiral anomaly-induced nonlinear planar effects was obtained. We conclude that the proposed behaviors of quantum oscillations in the nonlinear planar effects can uniquely identify the existence of the chiral anomaly in Weyl semimetals, especially when the sign of the chiral anomaly-driven longitudinal magnetoconductance is inconclusive according to recent theoretical work.
Article
Multidisciplinary Sciences
Mykola Telychko, Guangwu Li, Pingo Mutombo, Diego Soler-Polo, Xinnan Peng, Jie Su, Shaotang Song, Ming Joo Koh, Mark Edmonds, Pavel Jelinek, Jishan Wu, Jiong Lu
Summary: The study successfully achieved ultrahigh-yield synthesis of circumcoronene molecules on Cu(111) via surface-assisted intramolecular dehydrogenation, resulting in self-organization into an extended superlattice. The unique hexagonal zigzag topology of circumcoronenes and their nontrivial electronic properties on the metallic surface were revealed.
Article
Materials Science, Multidisciplinary
J. J. van den Broeke, I Swart, C. Morais Smith, D. Vanmaekelbergh
Summary: Muffin-tin methods have played a crucial role in designing honeycomb lattices with unique band structures, and further research is exploring the introduction of spin-orbit coupling to these systems to create topological gaps and a topological flat band.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Mingmin Zhong, Ying Liu, Feng Zhou, Minquan Kuang, Tie Yang, Xiaotian Wang, Gang Zhang
Summary: This study demonstrates the existence of perfect three-, four-, and sixfold degenerate phonons in Zr3Ni3Sb4, rather than in the electronic band structures. These nodal point phonons are robust to uniform strain and extend across the whole Brillouin zone, making them accessible for future experimental studies.
Article
Materials Science, Multidisciplinary
G. Giavaras
Summary: The energy spectrum of a graphene quantum dot formed between Landau levels can exhibit a simple pattern with energies coming from one of the two valleys only in the first Landau gap. This part of the spectrum has no crossings, specific angular momentum numbers, and large energy spacings, making it suitable for probing with standard spectroscopic techniques.
Article
Nanoscience & Nanotechnology
M. Ohno, M. Uchida, Y. Nakazawa, S. Sato, M. Kriener, A. Miyake, M. Tokunaga, Y. Taguchi, M. Kawasaki
Summary: This study successfully synthesized EuCdSb2 thin films with the largest B-site ionic radius, revealing its crystal structure and magnetic properties. This achievement paves the way for further exploration of novel Dirac materials using film techniques.
Article
Physics, Multidisciplinary
Wu Shi, Salman Kahn, Nicolas Leconte, Takashi Taniguchi, Kenji Watanabe, Michael Crommie, Jeil Jung, Alex Zettl
Summary: Recent studies have explored intriguing quantum phenomena in vdW heterostructures and superlattices but mainly focused on the moderate carrier density regime. In this study, we used a newly developed electron beam doping technique to probe high-temperature fractal BZ quantum oscillations in the extreme doping regimes. By accessing ultrahigh electron and hole densities beyond the dielectric breakdown limit, we observed nonmonotonic carrier-density dependence of fractal BZ states and up to fourth-order fractal BZ features. Theoretical simulations explained these findings as a weakening of superlattice effects at high carrier densities.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Adrian Pena
Summary: This paper investigates the scattering of electrons on a twisted light-driven graphene quantum dot, revealing the possibility of trapping incident electrons inside the dot for finite periods of time under certain scattering conditions. It also predicts that trapping times can be controlled using twisted light irradiation. The study was conducted for a frequency of the twisted light within the infrared spectrum.
Article
Physics, Applied
Zizhen Lin, Yanzheng Du, Peng Li, Cheng Chi, Yang Lu, Hao Dang, Dongxing Song, Weigang Ma, Yinshi Li, Xing Zhang
Summary: In this study, we developed a strategy to achieve metallic properties in semiconductor 3D graphene films by constructing wrinkles, which has potential applications in high-power nanoelectronics. The in situ construction of 1D metallic wrinkles provides a promising candidate as metallic wire interconnects in all-carbon electronics.
APPLIED PHYSICS LETTERS
(2022)
Article
Multidisciplinary Sciences
Niels C. H. Hesp, Iacopo Torre, David Barcons-Ruiz, Hanan Herzig Sheinfux, Kenji Watanabe, Takashi Taniguchi, Roshan Krishna Kumar, Frank H. L. Koppens
Summary: The study explores the photoresponse within a single moire unit cell of minimally twisted bilayer graphene using a nanoscale probe, revealing a spatially rich response influenced by the fine structure and orientation of the moire lattice. The measured spatial profile and carrier-density dependence of the photocurrent point towards a complex photo-thermoelectric response driven by the fine structure of the moire lattice.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Inorganic & Nuclear
Yuta Watanabe, Ryoji Suzuki, Kazuto Kato, Hisanori Yamane, Mamoru Kitaura, Toshiaki Ina, Kento Uchida, Yuta Matsushima
Summary: A new superionic Ag+ conductor with a high ionic conductivity was discovered in the AgI-Ag2CO3 system, which gradually decomposes at room temperature. The continuous distribution of Ag atoms in the crystal structure of the conductor was found to be associated with the conduction paths of Ag+ ions.
INORGANIC CHEMISTRY
(2021)
Article
Physics, Multidisciplinary
Kyung-Yong Park, Iksu Jang, Ki-Seok Kim, S. Kettemann
Summary: This study investigates the competition between IEC and Kondo effect in magnetic impurities, as well as the impact of RKKY correlations on these interactions, revealing that RKKY interaction enhances the inequality of Kondo temperatures. By extending the RKKY-coupled Kondo RG equations, the study examines the influence of this inequality on the distribution of Kondo temperatures in a system of magnetic impurities.
Article
Chemistry, Physical
Mamoru Kitaura, Kei Kamada, Toshiaki Ina, Hisanori Yamane, Manabu Ishizaki, Shinta Watanabe, Junpei Azuma, Isamu Yamamoto, Akimasa Ohnishi, Takeshi Usuki
Summary: The local structures of Gd atoms in Gd-3(Al, Ga)(5)O-12 garnet solid solutions grown using the Czochralski method were studied through X-ray and UV absorption spectroscopy experiments. The preferential sites for the occupation of Ga and Al atoms were identified, and positional fluctuations of neighboring O atoms buffered local distortions induced by the presence of Ga and Al atoms. Changes in high-resolution UV absorption spectra due to Gd intra-4f transitions on the Ga content were explained by considering crystal field and Coulomb repulsion on the Gd atom.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Optics
E. Feldbach, L. Museur, V. Krasnenko, A. Zerr, M. Kitaura, A. Kanaev
Summary: The formation and evolution of defect levels in the electronic structure of silicon nitride with cubic spinel structure, gamma-Si3N4, after irradiation with He+ ions were investigated using spectroscopic techniques. The changes in cathodoluminescence, photoluminescence, photoluminescence excitation, and Raman spectra were detected. The appearance of a new near-infrared band with close to band gap excitation was attributed to effective trapping of photoinduced electrons and holes by charged defects.
JOURNAL OF LUMINESCENCE
(2021)
Article
Physics, Applied
Mamoru Kitaura, Shinta Wantanabe, Toshiaki Ina, Motoharu Imai, Haruhiko Udono, Manabu Ishizaki, Hisanori Yamane, Taku Tanimoto, Akimasa Ohnishi
Summary: Investigating the local structures around Sb, Bi, and Ag dopant atoms in the environmentally friendly semiconductor Mg2Si using X-ray absorption spectroscopy at 10 K revealed that Sb and Bi predominantly occupy the 4a site, whereas Ag mainly resides at the 8c site, potentially partially occupying the 4b site. First-principles calculations provided insights into the characteristic change in second-neighbor distances around Ag atoms.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Mamoru Kitaura, Artoni Kevin R. Ang, Yuta Yamamoto, Naohisa Happo, Koji Kimura, Kouichi Hayashi, Shinta Watanabe, Yuui Yokota, Yuji Ohashi, Kei Kamada, Akira Yoshikawa, Hisanori Yamane, Akimasa Ohnishi
Summary: This study investigated the atomic positions and displacements of atoms around the Ta atom in piezoelectric materials CTGS and CTGAS using Ta-L alpha X-ray fluorescence holography. The experimental results were compared with simulated ones using SC-XRD, and the agreement between the two methods was found. The displacement of atoms relative to the Ta atom was qualitatively analyzed, and it was found that the Ca-O bond has a strong ionic character, which is responsible for the piezoelectricity in CTGS. The effect of Al substitution on piezoelectricity was also considered based on the change in the Ca-O bond.
FRONTIERS IN MATERIALS
(2022)
Article
Multidisciplinary Sciences
Jong E. Han, Camille Aron, Xi Chen, Ishiaka Mansaray, Jae-Ho Han, Ki-Seok Kim, Michael Randle, Jonathan P. Bird
Summary: The significant difference between predicted and experimental switching fields in correlated insulators under a far-from-equilibrium DC electric field necessitates a reevaluation of current microscopic understanding. The authors introduce a generic model of electrons coupled to an inelastic phononic medium and show that an electron avalanche can occur in the bulk limit of such insulators at arbitrarily small electric field. The quantum avalanche is triggered by the generation of in-gap states through a multi-phonon emission process, leading to a premature and partial collapse of the correlated gap.
NATURE COMMUNICATIONS
(2023)
Article
Nanoscience & Nanotechnology
Jin-Hyeon Jun, Jinsu Kim, Sang Hyun Ji, Sang-Eon Lee, Soo-Whan Kim, Sung Jung Joo, Kyoung-Min Kim, Ki-Seok Kim, Myung-Hwa Jung
Summary: We introduced magnetic order by substituting Gd at the Bi site and tuning the Fermi level by substituting Se at the Te site in a typical topological insulator, Bi2Te3. We obtained a material with x = 0.06 and y = 0.7, which exhibits the characteristics of an antiferromagnetic topological insulator and shows exotic magnetotransport properties.
Article
Astronomy & Astrophysics
Ki-Seok Kim, Mitsuhiro Nishida, Yoonseok Choun
Summary: By implementing a nonperturbative Wilsonian renormalization group (RG) transformation, we establish an effective holographic dual description with an emergent extradimension associated with an RG scale. In the large-N limit, we derive an equation of motion for an order-parameter field, such as the chiral condensate. We demonstrate an intertwined structure between the first-order RG flow equations and the second-order differential equation of the order-parameter field, leading to a nonperturbative RG-improved mean-field theory. Assuming translational symmetry as the vacuum state, we solve the nonlinear coupled mean-field equations by matching the UV and IR solutions, revealing an RG flow from a weakly coupled chiral-symmetric UV fixed point to a strongly correlated chiral-symmetry broken IR fixed point.
Article
Optics
L. Museur, E. Feldbach, A. Kotlov, M. Kitaura, A. Kanaev
Summary: The luminescence of MgAl2O4 was studied at cryogenic temperatures using synchrotron radiation and electron beam excitation. Antisite defects were found to be the main reason for the 5-eV luminescence, and further irradiation resulted in more intragap defect levels.
JOURNAL OF LUMINESCENCE
(2024)
Article
Astronomy & Astrophysics
Ki-Seok Kim
Summary: This study investigates disordered strongly coupled conformal field theories in the large central-charge limit. By considering a quenched average for metric fluctuations and the renormalization group flow of the metric-tensor distribution function, it is revealed that the renormalized distribution function universally shows a power-law behavior, interpreted as an infinite randomness fixed point.
Article
Materials Science, Multidisciplinary
Suik Cheon, Gil Young Cho, Ki-Seok Kim, Hyun-Woo Lee
Summary: This article discusses the possibility of realizing the chiral anomaly in noncentrosymmetric systems without pairs of Weyl points, where spin-orbit coupling induces nonzero Berry curvature flux through Fermi surfaces. This phenomenon affects both charge and spin transport properties, leading to the emergence of new physical effects.
Article
Astronomy & Astrophysics
Ki-Seok Kim, Shinsei Ryu, Kanghoon Lee
Summary: In holographic duality, a theory framework that describes the renormalization group flow of a quantum field theory by introducing additional dimensions, we develop a new holographic description that encodes the information of the renormalization group flow and the quantum field theory into an effective field theory. We demonstrate the self-consistency of this dual construction under the assumption of bulk locality.
Article
Materials Science, Multidisciplinary
Jinho Yang, Ki-seok Kim
Summary: The study verifies that emergent Lorentz symmetry and chiral anomaly can be measured in Shubnikov-de Haas (SdH) quantum oscillations. The double-peak structure in SdH oscillations is found to cause a kink in the Landau fan diagram.
Article
Crystallography
Ryoji Suzuki, Yuta Watanabe, Hisanori Yamane, Mamoru Kitaura, Kento Uchida, Yuta Matsushima
Summary: The new compound silver carbonate iodide, Ag-10(CO3)(3)I-4, has a unique layered crystal structure and is a precursor of the superionic conductor Ag-17(CO3)(3)I-11. It is prepared by heating a stoichiometric powder mixture of AgI and Ag2CO3 at 430 K, and its crystal structure was obtained by slow cooling of a melt with an AgI-rich composition. So far, Cs3Pb2(CO3)(3)I is the only other compound in the Inorganic Crystal Structure Database containing carbonate groups and iodide ions.
ACTA CRYSTALLOGRAPHICA SECTION E-CRYSTALLOGRAPHIC COMMUNICATIONS
(2021)
