Article
Multidisciplinary Sciences
H. Suzuki, H. Liu, J. Bertinshaw, K. Ueda, H. Kim, S. Laha, D. Weber, Z. Yang, L. Wang, H. Takahashi, K. Fuersich, M. Minola, B. V. Lotsch, B. J. Kim, H. Yavas, M. Daghofer, J. Chaloupka, G. Khaliullin, H. Gretarsson, B. Keimer
Summary: The study on alpha-RuCl3 reveals that its candidate status as a quantum spin liquid is compromised by the presence of zigzag antiferromagnetic order at low temperatures, which is destabilized by quantum fluctuations and ultimately leads to a ferromagnetic ground state. The competition among these three states, including ferromagnetism and the Kitaev spin liquid, is crucial for understanding the unusual properties of alpha-RuCl3 in magnetic fields.
NATURE COMMUNICATIONS
(2021)
Article
Nanoscience & Nanotechnology
Subin Kim, Bo Yuan, Young-June Kim
Summary: Quantum spin liquids, especially Kitaev's honeycomb model, are receiving significant attention as a potential platform for future quantum technologies. While theoretical studies have showcased intriguing properties of quantum spin liquids, experimental realization remains challenging. The recent observation of the quantized thermal Hall effect in alpha-RuCl(3) has brought us closer to experimental realization, yet conflicting results indicate the fragility of the Kitaev quantum spin liquid phase and its sensitivity to the sample. This article provides an overview of alpha-RuCl3 as a prime candidate material for realizing Kitaev quantum spin liquids, focusing on crystal growth methods and morphologies. Additionally, current research attempts to identify other candidate materials, particularly 3d transition-metal compounds, are discussed.
Article
Materials Science, Multidisciplinary
Vilmos Kocsis, David A. S. Kaib, Kira Riedl, Sebastian Gass, Paula Lampen-Kelley, David G. Mandrus, Stephen E. Nagler, Nicolas Perez, Kornelius Nielsch, Bernd Buechner, Anja U. B. Wolter, Roser Valenti
Summary: In this combined theoretical and experimental research, the anisotropic magnetic and magnetoelastic properties of the Kitaev material alpha-RuCl3 were investigated. Unusually large magnetostriction anisotropy and non-symmetric magnetic anisotropy were observed, and their origins were explained based on the relative orientation of the magnetization with respect to the crystal structure.
Article
Multidisciplinary Sciences
Haoxiang Li, T. T. Zhang, A. Said, G. Fabbris, D. G. Mazzone, J. Q. Yan, D. Mandrus, Gabor B. Halasz, S. Okamoto, S. Murakami, M. P. M. Dean, H. N. Lee, H. Miao
Summary: The study reveals a coupling between phonons and Kitaev magnetic excitations in alpha-RuCl3, where optical phonons show intensity enhancement near the Kitaev energy and giant phonon softening occurs near the Z(2) gauge flux energy scale.
NATURE COMMUNICATIONS
(2021)
Article
Chemistry, Physical
Bowen Yang, Yin Min Goh, Suk Hyun Sung, Gaihua Ye, Sananda Biswas, David A. S. Kaib, Ramesh Dhakal, Shaohua Yan, Chenghe Li, Shengwei Jiang, Fangchu Chen, Hechang Lei, Rui He, Roser Valenti, Stephen M. Winter, Robert Hovden, Adam W. Tsen
Summary: The authors investigate the magnetic anisotropy in monolayer RuCl3 and observe a transition from easy-plane to easy-axis due to in-plane distortions of Cl atoms. This finding is important for realizing a quantum spin liquid. The study provides insights into the possibility of exploring Kitaev physics in a true two-dimensional limit.
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.
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
Chemistry, Multidisciplinary
Bing Wang, Yaxuan Wu, Yihang Bai, Puyuan Shi, Guangbiao Zhang, Yungeng Zhang, Chang Liu
Summary: In this study, the triaxial magnetic anisotropic properties of a ferromagnetic semiconductor CrSBr monolayer were investigated by the first-principles method. The results showed that the triaxial magnetic anisotropy originated from the coexistence of the magnetic dipole-dipole interaction (shape anisotropy) and the spin-orbit coupling interaction (magnetocrystalline anisotropy). The dominant contribution to the magnetic anisotropy was found to be from the shape anisotropy. Furthermore, the easy magnetic axes and ferromagnetism in the CrSBr monolayer could be manipulated by strains, especially the uniaxial strain in the x direction.
Article
Materials Science, Multidisciplinary
Huimei Liu, Jiri Chaloupka, Giniyat Khaliullin
Summary: We conducted an analytical study on the exchange interactions between pseudospin one-half d(5) ions in honeycomb lattices with edge-shared octahedra. We considered various exchange channels including Hubbard U, charge-transfer excitations, and cyclic exchange, and included hoppings within t(2g) orbitals as well as between t(2g) and e(g) orbitals. Our study focused on the effects of the trigonal crystal field Delta on the exchange parameters. We found that the obtained exchange Hamiltonian is mainly dominated by ferromagnetic Kitaev interaction K within a wide range of Delta.
Article
Materials Science, Multidisciplinary
Ludwig Holleis, Joseph C. Prestigiacomo, Zhijie Fan, Satoshi Nishimoto, Michael Osofsky, Gia-Wei Chern, Jeroen van den Brink, B. S. Shivaram
Summary: The study on NL susceptibilities in the proximate Kitaev magnet alpha-RuCl3 shows distinct responses at low temperatures, as well as a unique cubic term at high temperatures.
NPJ QUANTUM MATERIALS
(2021)
Article
Nanoscience & Nanotechnology
J. A. N. Bruin, R. R. Claus, Y. Matsumoto, J. Nuss, S. Laha, B. V. Lotsch, N. Kurita, H. Tanaka, H. Takagi
Summary: This study conducted measurements of magnetothermal conductivity and magnetization at low temperatures for α-RuCl3 material, and found the presence of oscillatory and peak structures, which are attributed to field-induced phase transitions rather than quantum oscillations. Some of these features are temperature-dependent and connected to magnetic phase transitions at zero field.
Article
Chemistry, Physical
Yun-Yi Pai, Claire E. Marvinney, Matthew A. Feldman, Brian Lerner, Yoong Sheng Phang, Kai Xiao, Jiaqiang Yan, Liangbo Liang, Jason Lapano, Matthew Brahlek, Benjamin J. Lawrie
Summary: The study found that exfoliated alpha-RuCl3 flakes lack R (3) symmetrical phase at low temperatures, and the Raman modes exhibit unexpected stochastic shifts in response to the applied magnetic field, possibly due to the emergence of magnetostrictive interactions.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Review
Physics, Condensed Matter
A. Loidl, P. Lunkenheimer, V Tsurkan
Summary: This article provides an overview of recent thermodynamic, infrared, and THz studies on the proximate Kitaev spin-liquid, highlighting its unique properties and experimental evidence, along with comparisons to theoretical predictions and model calculations.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2021)
Article
Physics, Multidisciplinary
Xiaoxue Zhao, Kejing Ran, Jinghui Wang, Song Bao, Yanyan Shangguan, Zhentao Huang, Junbo Liao, Bo Zhang, Shufan Cheng, Hao Xu, Wei Wang, Zhao-Yang Dong, Siqin Meng, Zhilun Lu, Shin-ichiro Yano, Shun-Li Yu, Jian-Xin Li, Jinsheng Wen
Summary: Experimental study on the evolution of magnetic excitations of α-RuCl3 under an in-plane magnetic field reveals the emergence of a pure QSL state near the critical field. This suggests that an in-plane magnetic field can drive α-RuCl3 into the long-sought QSL state.
CHINESE PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Yunpeng Wu, Deyang Yu, Yi Feng, Leiyun Han, Xilong Liu, Xudong Zhao, Xiaoyang Liu
Summary: This paper presents a new method to synthesize ferromagnetic graphene by nitrogen doping, and characterizes the material using XPS, Raman spectroscopy, and SQUID. The results show that when the nitrogen doping reaches a certain threshold, graphene exhibits ferromagnetism.
CHINESE CHEMICAL LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Subin Kim, Bo Yuan, Young-June Kim
Summary: Quantum spin liquids, especially Kitaev's honeycomb model, are receiving significant attention as a potential platform for future quantum technologies. While theoretical studies have showcased intriguing properties of quantum spin liquids, experimental realization remains challenging. The recent observation of the quantized thermal Hall effect in alpha-RuCl(3) has brought us closer to experimental realization, yet conflicting results indicate the fragility of the Kitaev quantum spin liquid phase and its sensitivity to the sample. This article provides an overview of alpha-RuCl3 as a prime candidate material for realizing Kitaev quantum spin liquids, focusing on crystal growth methods and morphologies. Additionally, current research attempts to identify other candidate materials, particularly 3d transition-metal compounds, are discussed.
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)
Article
Multidisciplinary Sciences
Jian-Rui Soh, Alessandro Bombardi, Frederic Mila, Marein C. Rahn, Dharmalingam Prabhakaran, Sonia Francoual, Henrik M. Ronow, Andrew T. Boothroyd
Summary: Resonant elastic X-Ray scattering on EuIn2As2 reveals that the magnetic order in this material satisfies the symmetry requirements for it to be an axion insulator. This finding is significant and may contribute to a better understanding of the physical properties of magnetic topological insulators.
NATURE COMMUNICATIONS
(2023)
Article
Crystallography
Randy Belanger, James Patrick Clancy, Sheetal Jain, Zahra Yamani, Yu-Chih Tseng, Young-June Kim
Summary: We present the results of inelastic neutron scattering (INS) measurements on the phonon dispersion relation in higher manganese silicides (HMSs). A large single crystal ingot of HMS is synthesized using a slow cooling technique, with Mn15Si26 identified as the primary phase. The sample consists of highly oriented crystallites as confirmed by neutron pole-figure study and thermal conductivity data. Our INS results generally agree with previous experimental and theoretical studies on phonons in HMS; however, we also observe some discrepancies, such as a 5 meV gap at the zone center and a softer dispersion relation for the low-lying twisting mode. We discuss the possible origins of these observations and their implications for the thermal properties of HMS.
Article
Physics, Multidisciplinary
Hyeok-Jun Yang, Hee Seung Kim, Min Yong Jeong, Yong Baek Kim, Myung Joon Han, SungBin Lee
Summary: The nature of superconductivity in recently discovered kagome materials AV(3)Sb(5) (A = K, Rb, Cs) has been heavily debated. Recent experiments indicate the presence of orbital current order in addition to charge density wave (CDW) and superconductivity. This study investigates the mutual influence between orbital current order and superconductivity in kagome metals with characteristic van Hove singularity (vHS). By deriving the Landau-Ginzburg theory, possible orbital current orders and superconductivities are classified, leading to the expectation of distinct unconventional superconductivities depending on the type of orbital current ordering. This information can help infer the superconducting order parameter when identifying orbital current order and vice versa. Possible experiments to differentiate such coexisting superconducting states and orbital current order are also discussed.
SCIPOST PHYSICS CORE
(2023)
Article
Physics, Multidisciplinary
Wolfgang Simeth, Andreas Bauer, Christian Franz, Aisha Aqeel, Pablo J. Bereciartua, Jennifer A. Sears, Sonia Francoual, Christian H. Back, Christian Pfleiderer
Summary: We present resonant elastic x-ray scattering results on EuPtSi3, revealing a combination of magnetic phases suggesting a highly unusual competition between antiferromagnetic exchange interactions with Dzyaloshinsky-Moriya spin-orbit coupling of similar strength. By utilizing different scattering geometries and full linear polarization analysis, we unambiguously identify magnetic scattering contributions. The phase diagram of EuPtSi3 includes various long-wavelength modulations and distinct superstructures for different magnetic field orientations.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Dirk Wulferding, Junkyoung Kim, Mi Kyung Kim, Yang Yang, Jae Hyuck Lee, Dongjoon Song, Dongjin Oh, Heung-Sik Kim, Li Ern Chern, Yong Baek Kim, Minji Noh, Hyunyong Choi, Sungkyun Choi, Natalia B. Perkins, Changyoung Kim, Seung Ryong Park
Summary: The study reveals two successive phase transitions in the pyrochlore magnet Nd2Ru2O7 at high temperatures, leading to giant phonon instabilities and the emergence of a highly coherent excitation. This excitation, a collective Higgs-type amplitude mode, stabilizes at a low energy of 3 meV and involves bond energy modulations of the Ru-4 tetrahedra. Its two-fold symmetry, incompatible with the crystal structure, highlights the possibility of multiple entangled broken symmetries.
NPJ QUANTUM MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Felix Desrochers, Li Ern Chern, Yong Baek Kim
Summary: Studying symmetry fractionalization in quantum spin ice is important for understanding its properties and experimental signatures, and a new framework has been developed to classify different symmetry-enriched topological phases.
Article
Materials Science, Multidisciplinary
J. P. Clancy, H. Gretarsson, A. Lupascu, J. A. Sears, Z. Nie, M. H. Upton, Jungho Kim, Z. Islam, M. Uchida, D. G. Schlom, K. M. Shen, Young -June Kim
Summary: We investigated the magnetic and spin-orbit excitations of ultrathin epitaxial films of Ba2IrO4 using resonant inelastic x-ray scattering, and compared them with their sister compound Sr2IrO4. Due to the 180 degrees Ir-O-Ir bond, the magnon and spin orbiton in Ba2IrO4 have a significantly larger bandwidth, making it challenging to describe these excitations as separate quasiparticles. Both types of excitations are sensitive to epitaxial strain. Additionally, the d-level inversion observed in Sr2IrO4 is not present in Ba2IrO4, as predicted by recent theoretical studies. Our results highlight the substantial differences in the magnetic properties of Ba2IrO4 and Sr2IrO4, suggesting a need for a careful examination of these materials considering electron itinerancy.
Article
Materials Science, Multidisciplinary
Etienne Lefrancois, Jordan Baglo, Q. Barthelemy, S. Kim, Young -June Kim, Louis Taillefer
Summary: The two-dimensional layered insulator alpha-RuCl3 is a potential material for a quantum spin-liquid state. We measured the thermal conductivity of alpha-RuCl3 as a function of magnetic field in two in-plane directions and found that the oscillations between the critical field B-c and B* are the same for both field directions.
Article
Materials Science, Multidisciplinary
Omid Tavakol, Yong Baek Kim
Summary: Nonlinear optical responses in topological semimetals, such as shift current and second-harmonic generation (SHG), are of great interest due to the large responses arising from the momentum-space topological structures. Nodal line semimetals can offer even larger responses at low frequencies, with the SHG response being significantly enhanced by breaking the inversion symmetry. Additionally, a model with intrinsically broken inversion symmetry exhibits singular shift current and SHG responses within a range of parameters.
Article
Materials Science, Multidisciplinary
Blair W. Lebert, Subin Kim, Beom Hyun Kim, Sae Hwan Chun, Diego Casa, Jaewon Choi, Stefano Agrestini, Kejin Zhou, Mirian Garcia-Fernandez, Young -June Kim
Summary: A comparative study of three well-known Kitaev materials, alpha-Li2IrO3, Na2IrO3, and alpha-RuCl3, was conducted using resonant inelastic x-ray scattering (RIXS). Despite similar low-energy physics, these materials exhibit distinct electronic properties, such as the size difference of the charge gap. The RIXS spectra of the spin-orbit exciton for these materials show remarkably similar three-peak features, indicating the significant role of nonlocal physics in their electronic structure. The study suggests that while a spin-orbit assisted Mott insulator is still the best description for these materials, electron itinerancy cannot be ignored in formulating their low-energy Hamiltonian.
Article
Materials Science, Multidisciplinary
Finn Lasse Buessen, Hyun-Yong Lee, Tarun Grover, Yong Baek Kim
Summary: In this study, we investigate the nonequilibrium states of an interacting multicomponent quantum system when only an extensive subsystem is quantum quenched or driven from the ground state. Using density matrix renormalization group simulations and various entanglement entropy diagnostics, we study the effect of quenching and driving of the transverse field in a system comprised of two XXZ spin chains and a transverse field Ising chain.
