Article
Materials Science, Multidisciplinary
Alexandros Metavitsiadis, Wolfram Brenig
Summary: The study examines the energy-density dynamics of the two-dimensional Kitaev spin model on the honeycomb lattice at finite momentum. It highlights the influence of thermally induced disorder and two distinct relaxation channels on the coherent low-temperature energy-density dynamics. The analysis is based on complementary calculations and mean-field treatment of thermal gauge fluctuations.
Article
Chemistry, Physical
Peter Czajka, Tong Gao, Max Hirschberger, Paula Lampen-Kelley, Arnab Banerjee, Nicholas Quirk, David G. Mandrus, Stephen E. Nagler, N. P. Ong
Summary: This study provides detailed measurements of the thermal Hall conductivity k(xy) in alpha-RuCl3. It is found that k(xy) strongly depends on temperature between 0.5 and 10K. The spin excitations evolve into magnon-like modes with a Chern number of approximately 1 at high magnetic fields, instead of showing the expected half-quantization effect of k(xy)/T.
Review
Physics, Multidisciplinary
Simon Trebst, Ciaran Hickey
Summary: In transition-metal compounds, Kitaev materials with spin-orbit entanglement, electronic correlations, and crystal-field effects have been synthesized, leading to various forms of topological quantum matter. The theoretical and experimental exploration of these materials is of great interest for unconventional forms of magnetism.
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Sparsh Mishra, Shun Tamura, Akito Kobayashi, Yukio Tanaka
Summary: The study reveals that the spatial distribution of the local density of states and the odd-frequency spin-triplet s-wave pair amplitude can be tuned when the impurity is positioned close to the edge. Additionally, the zero-energy local density of states and low-frequency odd-frequency pair amplitude exhibit the same spatial dependence.
Article
Materials Science, Multidisciplinary
Kazuki Nakazawa, Yasuyuki Kato, Yukitoshi Motome
Summary: This article presents theoretical results on the Majorana band structure and thermal transport properties in the Kitaev honeycomb model under a staggered magnetic field in addition to a uniform one. It is found that the asymmetric deformation of the Majorana band leads to nonreciprocal thermal transport, and the field dependence of the thermal conductivity is correlated with the magnitude of the Majorana gap and the asymmetry of the Majorana excitation spectra. The estimates of thermal currents are shown, and it is discussed that the linear response is experimentally measurable while improvement is needed for observing the nonlinear one.
Article
Astronomy & Astrophysics
Antonio M. Garcia-Garcia, Victor Godet
Summary: In this study, a two-site Sachdev-Ye-Kitaev (SYK) model with complex couplings is investigated, and a low temperature transition to a gapped phase characterized by a constant in temperature free energy is identified. A gravity interpretation of these results is proposed by constructing an explicit solution of Jackiw-Teitelboim gravity with matter, which involves a two-dimensional Euclidean wormhole with the geometry of a double trumpet. This transition from a disconnected phase with two black holes to the connected wormhole phase is observed as the temperature decreases, demonstrating how a Euclidean wormhole can arise from an average over field theory couplings.
Article
Materials Science, Multidisciplinary
Aman Kumar, Vikram Tripathi
Summary: We investigate the thermal Hall conductivity k(xy) in a J-K Kitaev-Heisenberg model with a Zeeman field in the (111) direction, to understand the relationship between the possible reemergence of Ising topological order (ITO) and the half-quantized K-xy/T upon field suppression of long-range magnetic order in Kitaev materials. We use a purification-based finite-temperature tensor network approach without assuming the nature of the excitations: Majorana, visons, or spin waves. Our results show that the half-quantized thermal Hall effect near field-suppressed magnetic order is a fine-tuning effect and is not associated with a Majorana Hall state with ITO.
Article
Physics, Multidisciplinary
Bryce Kobrin, Zhenbin Yang, Gregory D. Kahanamoku-Meyer, Christopher T. Olund, Joel E. Moore, Douglas Stanford, Norman Y. Yao
Summary: Researchers have utilized massively parallel, matrix-free Krylov subspace methods to study dynamical correlators in the Sachdev-Ye-Kitaev model, finding agreement with dynamical mean field solutions at high temperatures and accurate reproduction of finite-size corrections at low temperatures using the dynamics of near extremal black holes. They have also developed a novel finite-size rescaling procedure for analyzing the growth of out-of-time-order correlators and accurately determining the Lyapunov exponent across a wide range of temperatures.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Joshuah T. Heath, Faranak Bahrami, Sangyun Lee, Roman Movshovich, Xiao Chen, Fazel Tafti, Kevin Bedell
Summary: In this study, the authors use the analytical paradigm of Landau-Fermi liquid theory to identify thermodynamic features of itinerant Majorana fermions and compare them with experimental data from the Kitaev spin liquid candidate Ag3LiIr2O6. Their findings provide strong evidence for a Fermi liquid-like ground state and open up new avenues for detecting itinerant Majorana fermions in condensed matter systems.
COMMUNICATIONS PHYSICS
(2023)
Article
Physics, Multidisciplinary
Umberto Borla, Ruben Verresen, Jeet Shah, Sergej Moroz
Summary: The study reveals the existence of fermion parity symmetry in the Kitaev chain, with gauge transformation leading to a topological order distinct from the Kitaev chain. The deconfined phase can remain stable even in the presence of vortices. Additionally, a comprehensive study of a model interpolating between ordinary and gauged Kitaev chains showcases rich quantum criticality.
Article
Materials Science, Multidisciplinary
Natalia Chepiga, Frederic Mila
Summary: We demonstrate in this study that incorporating pairing and repulsion into the description of one-dimensional spinless fermions, as in the domain wall theory of commensurate melting or the interacting Kitaev chain, results in a line of critical points in the eight-vertex universality class for strong repulsion. These critical points terminate the floating phases and exhibit emergent U (1) symmetry. Through extensive density matrix renormalization group (DMRG) simulations of the entire phase diagram, it is confirmed that the variation of the critical exponents along the line, derived from Baxter's exact solution of the XYZ chain at J(x) = -J(z), is fully supported. The qualitative features of the phase diagram are found to be independent of the specific form of the interactions.
Article
Physics, Multidisciplinary
C. M. Morris, Nisheeta Desai, J. Viirok, D. Huvonen, U. Nagel, T. Room, J. W. Krizan, R. J. Cava, T. M. McQueen, S. M. Koohpayeh, Ribhu K. Kaul, N. P. Armitage
Summary: The terahertz spectroscopic study of quasi-one-dimensional ferromagnet CoNb2O6 reveals bond-dependent interactions similar to the one-dimensional honeycomb Kitaev spin liquid. The material is shown to be described by a 'twisted Kitaev chain' model, deviating from the Ising chain model. The ferromagnetic ground state arises from a compromise between two axes, leading to quantum motion of domain walls and potential for quantum spin liquid behavior in Co2+ magnets.
Article
Materials Science, Multidisciplinary
Haining Pan, Sankar Das Sarma
Summary: Motivated by the presence of Majorana zero modes in both the Kitaev chain model and the experimental semiconductor-superconductor Majorana nanowire, this theoretical study investigates the equivalence or similarity between the two models from the perspective of their corresponding dual spin models. By using the Jordan-Wigner transformation, the duality between the Kitaev chain and the transverse-field XY spin model is established, aiming to connect the Kitaev chain and the nanowire. The application of the Jordan-Wigner transformation to the nanowire reveals that the corresponding bosonic spin model is a generalized spin cluster model with staggered couplings. By projecting out the higher energy band of the spinful nanowire system, an effective low-energy spinless system is obtained, leading to the connection between the Kitaev chain and Majorana nanowire.
Article
Physics, Multidisciplinary
Shao-Kai Jian, Chunxiao Liu, Xiao Chen, Brian Swingle, Pengfei Zhang
Summary: In this study, Brownian SYK chains subjected to continuous monitoring were constructed to explore entanglement phase transitions. It was found that the entanglement transition is caused by symmetry breaking in the enlarged replica space, with a continuous O(2) symmetry between replicas in the noninteracting case leading to spontaneous breaking upon varying the measurement rate. The results suggest that the emergent replica criticality associated with the Goldstone mode leads to log-scaling entanglement entropy in the symmetry broken phase at low measurement rate, while area-law scaling is observed in the symmetric phase at higher measurement rate.
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
Thomas Halloran, Felix Desrochers, Emily Z. Zhang, Tong Chen, Li Ern Chern, Zhijun Xu, Barry Winn, M. Graves-Brook, M. B. Stone, Alexander I. Kolesnikov, Yiming Qiu, Ruidan Zhong, Robert Cava, Yong Baek Kim, Collin Broholm
Summary: Recently, Co-based honeycomb magnets have been proposed as promising candidate materials for Kitaev spin liquid. This study presents and analyzes an inelastic neutron scattering (INS) study of BaCo2(AsO4)2 (BCAO) with fields in the honeycomb plane. The results suggest that the XXZ-J1-J3 model, rather than the JKF F' model, can account for the experimental data consistently.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Correction
Physics, Multidisciplinary
Joji Nasu, Junki Yoshitake, Yukitoshi Motome
PHYSICAL REVIEW LETTERS
(2021)
Article
Multidisciplinary Sciences
T. Yokoi, S. Ma, Y. Kasahara, S. Kasahara, T. Shibauchi, N. Kurita, H. Tanaka, J. Nasu, Y. Motome, C. Hickey, S. Trebst, Y. Matsuda
Summary: Recent reports have shown the presence of half-integer thermal quantum Hall conductance in the two-dimensional honeycomb material alpha-RuCl3, even in magnetic fields without out-of-plane components. The measured field-angular variation of the quantized thermal Hall conductance in alpha-RuCl3 has the same sign structure as the topological Chern number of the pure Kitaev spin liquid, indicating that the non-Abelian topological order persists in the presence of non-Kitaev interactions.
Article
Physics, Multidisciplinary
Shota Suetsugu, Yuzuki Ukai, Masaki Shimomura, Masashi Kamimura, Tomoya Asaba, Yuichi Kasahara, Nobuyuki Kurita, Hidekazu Tanaka, Takasada Shibauchi, Joji Nasu, Yukitoshi Motome, Yuji Matsuda
Summary: Researchers have found that the Kitaev quantum spin liquid on the two-dimensional honeycomb lattice undergoes a phase transition at intense magnetic fields, which may be a weak first-order transition. This transition affects the thermal Hall conductance of the topological state.
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
(2022)
Article
Multidisciplinary Sciences
Akihiko Ikeda, Yasuhiro H. Matsuda, Keisuke Sato, Yuto Ishii, Hironobu Sawabe, Daisuke Nakamura, Shojiro Takeyama, Joji Nasu
Summary: This study unveils the exotic phase diagram of LaCoO3 under ultrahigh magnetic fields and reveals the emergence of two distinct spin-triplet exciton condensates. The continuous magnetostriction curves and bending structure are found, indicating the field-induced successive transitions. Quantum fluctuations of excitons are shown to be crucial for these transitions. The spin-triplet exciton condensation in a cobaltite provides a novel venue for spintronics technologies.
NATURE COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Kiyu Fukui, Yasuyuki Kato, Joji Nasu, Yukitoshi Motome
Summary: In this study, we investigated the spin-S Kitaev-Heisenberg models and found that quantum spin liquid phases are more stable compared to ordered phases in high spin cases.
Article
Materials Science, Multidisciplinary
Kiyu Fukui, Yasuyuki Kato, Joji Nasu, Yukitoshi Motome
Summary: In this study, the effects of Kitaev-type interactions on ultracold polar molecules were investigated using the pseudofermion functional renormalization group method. The results show that regardless of the spatial anisotropy of the interactions, the ground state exhibits magnetic order, and the case with isotropic interactions is closest to realizing the Kitaev quantum spin liquid. By introducing a cutoff in the interaction range, it was shown how the long-range interactions destroy the Kitaev quantum spin liquid.
Article
Materials Science, Multidisciplinary
Joji Nasu, Yuta Murakami, Akihisa Koga
Summary: This study focuses on spin transport in the presence of excited fluxes and reports strong interference effects in the propagation of Majorana fermions. Excited fluxes alter all transfer integrals on the string connecting them, leading to enhanced spatial modulation.
Article
Materials Science, Multidisciplinary
Joji Nasu, Satoru Hayami
Summary: We investigated the electric polarizations that occur perpendicular to an applied thermal gradient in insulating systems and focused on the antisymmetric component of the thermopolarization tensor. We found that this component becomes nonzero due to the presence of electric-toroidal dipole moments with ferrotype order. By studying localized electronic clouds, we developed a model and discovered a vortex-type configuration of local electric polarizations as the mean-field ground state. The coefficient of the thermopolarization was calculated based on linear-response theory, and it was determined that fluctuations in the p orbitals are crucial for enhancing the antisymmetric thermopolarization. The appearance conditions and relevance to real materials were also discussed.
Article
Materials Science, Multidisciplinary
Taishun Manjo, Shunsuke Kitou, Naoyuki Katayama, Shin Nakamura, Takuro Katsufuji, Yoichi Nii, Taka-hisa Arima, Joji Nasu, Takumi Hasegawa, Kunihisa Sugimoto, Daisuke Ishikawa, Alfred Q. R. Baron, Hiroshi Sawa
Summary: High-precision diffraction data obtained by synchrotron radiation X-rays can be used to observe the anisotropy of degenerate orbital states, and the orbital quantum state can be successfully determined from this anisotropy.
MATERIALS ADVANCES
(2022)
Article
Materials Science, Multidisciplinary
Hirokazu Taguchi, Yuta Murakami, Akihisa Koga, Joji Nasu
Summary: In this study, the impact of anisotropy on spin propagation in a quantum spin Kitaev model with zigzag edges was investigated. It was found that for small anisotropy, the spin propagation velocity matches the group velocity of itinerant Majorana fermions, while in a gapped system with large anisotropy, spin propagation is strongly suppressed. The study also addressed spin transport in junction systems described by Kitaev models with different anisotropies.
Article
Materials Science, Multidisciplinary
Shinnosuke Koyama, Joji Nasu
Summary: The study on magnetic excitations and thermal Hall effect on the Kitaev-Heisenberg model reveals that the thermal Hall conductivity is sensitive to the spin ordered pattern and excitation spectra, and can be enhanced under certain conditions. Additionally, a common feature in the field-angle dependence is found, with the conductivity vanishing on planes spanned by the spin axes.
Article
Materials Science, Multidisciplinary
Joji Nasu, Yukitoshi Motome
Summary: The study investigates the impact of two types of disorder on spin dynamics in the Kitaev model on a honeycomb lattice, revealing that disorder affects the energy spectrum of spin excitations, including peaks from flux and Majorana excitations. Different types of disorder have distinct effects on the low-temperature behavior of the magnetic susceptibility and NMR relaxation rate.
Article
Materials Science, Multidisciplinary
Akihisa Koga, Yuta Murakami, Joji Nasu
Summary: Researchers investigated the effects of flux configurations on emergent Majorana fermions in the S = 1/2 Kitaev model on a honeycomb lattice. They found that periodically arranged flux configurations result in low-energy excitations that are distinctly different from the flux-free state. The study's findings could be crucial in controlling the motion of Majorana fermions and spin excitations in Kitaev candidate materials.
Proceedings Paper
Physics, Applied
Akihisa Koga, Yusuke Kamogawa, Joji Nasu
Summary: This study investigates a ferromagnetic instability in a single-band Hubbard model on the hypercubic lattice away from half filling. By utilizing dynamical mean-field theory and continuous-time quantum Monte Carlo simulations, it systematically calculates the magnetic susceptibility in both weak and strong coupling regions. The research also explores how ferromagnetic fluctuations are amplified under varying interaction strengths and hole densities, while addressing the efficiency of double flip updates in Monte Carlo simulations.
PROCEEDINGS OF THE 14TH ASIA-PACIFIC PHYSICS CONFERENCE
(2021)
Article
Materials Science, Multidisciplinary
Joji Nasu, Makoto Naka
Summary: The study reveals a spin Seebeck effect caused by excitonic condensation in a nonmagnetic insulator, where a spin current generated by a thermal gradient is observed in the excitonic insulating state, originating from spin-split collective excitation modes.