1
|
Akram M, Kapeghian J, Das J, Valentí R, Botana AS, Erten O. Theory of Moiré Magnetism in Twisted Bilayer α-RuCl 3. NANO LETTERS 2024; 24:890-896. [PMID: 38198643 DOI: 10.1021/acs.nanolett.3c04084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2024]
Abstract
Motivated by the recent developments in moiré superlattices of van der Waals magnets and the desire to control the magnetic interactions of α-RuCl3, here we present a comprehensive theory of the long-range ordered magnetic phases of twisted bilayer α-RuCl3. Using a combination of first-principles calculations and atomistic simulations, we show that the stacking-dependent interlayer exchange gives rise to an array of magnetic phases that can be realized by controlling the twist angle. In particular, we discover a complex hexagonal domain structure in which multiple zigzag orders coexist. This multidomain order minimizes the interlayer energy while enduring the energy cost due to domain wall formation. Further, we show that quantum fluctuations can be enhanced across the phase transitions. Our results indicate that magnetic frustration due to stacking-dependent interlayer exchange in moiré superlattices can be exploited to tune quantum fluctuations and the magnetic ground state of α-RuCl3.
Collapse
Affiliation(s)
- Muhammad Akram
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
- Department of Physics, Balochistan University of Information Technology, Engineering and Management Sciences (BUITEMS), Quetta 87300, Pakistan
| | - Jesse Kapeghian
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Jyotirish Das
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
| | - Antia S Botana
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| | - Onur Erten
- Department of Physics, Arizona State University, Tempe, Arizona 85287, United States
| |
Collapse
|
2
|
Zhou XG, Li H, Matsuda YH, Matsuo A, Li W, Kurita N, Su G, Kindo K, Tanaka H. Possible intermediate quantum spin liquid phase in α-RuCl 3 under high magnetic fields up to 100 T. Nat Commun 2023; 14:5613. [PMID: 37699909 PMCID: PMC10497594 DOI: 10.1038/s41467-023-41232-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 08/23/2023] [Indexed: 09/14/2023] Open
Abstract
Pursuing the exotic quantum spin liquid (QSL) state in the Kitaev material α-RuCl3 has intrigued great research interest recently. A fascinating question is on the possible existence of a field-induced QSL phase in this compound. Here we perform high-field magnetization measurements of α-RuCl3 up to 102 T employing the non-destructive and destructive pulsed magnets. Under the out-of-plane field along the c* axis (i.e., perpendicular to the honeycomb plane), two quantum phase transitions are uncovered at respectively 35 T and about 83 T, between which lies an intermediate phase as the predicted QSL. This is in sharp contrast to the case with in-plane fields, where a single transition is found at around 7 T and the intermediate QSL phase is absent instead. By measuring the magnetization data with fields tilted from the c* axis up to 90° (i.e., in-plane direction), we obtain the field-angle phase diagram that contains the zigzag, paramagnetic, and QSL phases. Based on the K-J-Γ-[Formula: see text] model for α-RuCl3 with a large Kitaev term we perform density matrix renormalization group simulations and reproduce the quantum phase diagram in excellent agreement with experiments.
Collapse
Affiliation(s)
- Xu-Guang Zhou
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Han Li
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, China
- Peng Huanwu Collaborative Center for Research and Education & School of Physics, Beihang University, 100191, Beijing, China
| | - Yasuhiro H Matsuda
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan.
| | - Akira Matsuo
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Wei Li
- Peng Huanwu Collaborative Center for Research and Education & School of Physics, Beihang University, 100191, Beijing, China.
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Nobuyuki Kurita
- Department of Physics, Tokyo Institute of Technology, Tokyo, 152-8551, Japan
| | - Gang Su
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, 100190, Beijing, China
| | - Koichi Kindo
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - Hidekazu Tanaka
- Department of Physics, Tokyo Institute of Technology, Tokyo, 152-8551, Japan
| |
Collapse
|
3
|
Lu W, Lee H, Cha J, Zhang J, Chung I. Electronic Structure Manipulation of the Mott Insulator RuCl 3 via Single-Crystal to Single-Crystal Topotactic Transformation. Angew Chem Int Ed Engl 2023; 62:e202219344. [PMID: 36861901 DOI: 10.1002/anie.202219344] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/16/2023] [Accepted: 03/02/2023] [Indexed: 03/03/2023]
Abstract
The core task for Mott insulators includes how rigid distributions of electrons evolve and how these induce exotic physical phenomena. However, it is highly challenging to chemically dope Mott insulators to tune properties. Herein, we report how to tailor electronic structures of the honeycomb Mott insulator RuCl3 employing a facile and reversible single-crystal to single-crystal intercalation process. The resulting product (NH4 )0.5 RuCl3 ⋅1.5 H2 O forms a new hybrid superlattice of alternating RuCl3 monolayers with NH4 + and H2 O molecules. Its manipulated electronic structure markedly shrinks the Mott-Hubbard gap from 1.2 to 0.7 eV. Its electrical conductivity increases by more than 103 folds. This arises from concurrently enhanced carrier concentration and mobility in contrary to the general physics rule of their inverse proportionality. We show topotactic and topochemical intercalation chemistry to control Mott insulators, escalating the prospect of discovering exotic physical phenomena.
Collapse
Affiliation(s)
- Weiqun Lu
- School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea
| | - Hyungseok Lee
- School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| | - Joonil Cha
- School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| | - Jian Zhang
- School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea
- Key Lab of Photovoltaic and Energy Conservation Materials, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - In Chung
- School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
| |
Collapse
|
4
|
Yang B, Goh YM, Sung SH, Ye G, Biswas S, Kaib DAS, Dhakal R, Yan S, Li C, Jiang S, Chen F, Lei H, He R, Valentí R, Winter SM, Hovden R, Tsen AW. Magnetic anisotropy reversal driven by structural symmetry-breaking in monolayer α-RuCl 3. NATURE MATERIALS 2023; 22:50-57. [PMID: 36396963 DOI: 10.1038/s41563-022-01401-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
Layered α-RuCl3 is a promising material to potentially realize the long-sought Kitaev quantum spin liquid with fractionalized excitations. While evidence of this state has been reported under a modest in-plane magnetic field, such behaviour is largely inconsistent with theoretical expectations of spin liquid phases emerging only in out-of-plane fields. These predicted field-induced states have been largely out of reach due to the strong easy-plane anisotropy of bulk crystals, however. We use a combination of tunnelling spectroscopy, magnetotransport, electron diffraction and ab initio calculations to study the layer-dependent magnons, magnetic anisotropy, structure and exchange coupling in atomically thin samples. Due to picoscale distortions, the sign of the average off-diagonal exchange changes in monolayer α-RuCl3, leading to a reversal of spin anisotropy to easy-axis anisotropy, while the Kitaev interaction is concomitantly enhanced. Our work opens the door to the possible exploration of Kitaev physics in the true two-dimensional limit.
Collapse
Affiliation(s)
- Bowen Yang
- Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Yin Min Goh
- Department of Physics, University of Michigan, Ann Arbor, MI, USA
| | - Suk Hyun Sung
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Gaihua Ye
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX, USA
| | - Sananda Biswas
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - David A S Kaib
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - Ramesh Dhakal
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC, USA
| | - Shaohua Yan
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, China
| | - Chenghe Li
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, China
| | - Shengwei Jiang
- Department of Physics, Cornell University, Ithaca, NY, USA
- Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
| | - Fangchu Chen
- Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada
- Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario, Canada
| | - Hechang Lei
- Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing, China
| | - Rui He
- Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, TX, USA
| | - Roser Valentí
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - Stephen M Winter
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC, USA.
| | - Robert Hovden
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
- Applied Physics Program, University of Michigan, Ann Arbor, MI, USA.
| | - Adam W Tsen
- Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario, Canada.
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada.
| |
Collapse
|
5
|
Liu Y, Slagle K, Burch KS, Alicea J. Dynamical Anyon Generation in Kitaev Honeycomb Non-Abelian Spin Liquids. PHYSICAL REVIEW LETTERS 2022; 129:037201. [PMID: 35905346 DOI: 10.1103/physrevlett.129.037201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 06/22/2022] [Indexed: 06/15/2023]
Abstract
Relativistic Mott insulators known as "Kitaev materials" potentially realize spin liquids hosting non-Abelian anyons. Motivated by fault-tolerant quantum-computing applications in this setting, we introduce a dynamical anyon-generation protocol that exploits universal edge physics. The setup features holes in the spin liquid, which define energetically cheap locations for non-Abelian anyons, connected by a narrow bridge that can be tuned between spin liquid and topologically trivial phases. We show that modulating the bridge from trivial to spin liquid over intermediate time scales-quantified by analytics and extensive simulations-deposits non-Abelian anyons into the holes with O(1) probability. The required bridge manipulations can be implemented by integrating the Kitaev material into magnetic tunnel junction arrays that engender locally tunable exchange fields. Combined with existing readout strategies, our protocol reveals a path to topological qubit experiments in Kitaev materials at zero applied magnetic field.
Collapse
Affiliation(s)
- Yue Liu
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - Kevin Slagle
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA
| | - Kenneth S Burch
- Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - Jason Alicea
- Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
- Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA
| |
Collapse
|
6
|
Loidl A, Lunkenheimer P, Tsurkan V. On the proximate Kitaev quantum-spin liquid α-RuCl 3: thermodynamics, excitations and continua. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:443004. [PMID: 34371492 DOI: 10.1088/1361-648x/ac1bcf] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/09/2021] [Indexed: 06/13/2023]
Abstract
This topical review provides an overview over recent thermodynamic, infrared, and THz results on the proximate Kitaev spin-liquid. Quantum-spin liquids are exotic phases characterized by the absence of magnetic ordering even at the lowest temperatures and by the occurrence of fractionalized spin excitations. Among those, Kitaev spin liquids are most fascinating as they belong to the rare class of model systems, that can be solved analytically by decomposing localized spinsS= 1/2 into Majorana fermions. The main aim of this review is to summarize experimental evidence obtained by THz spectroscopy and utilizing heat-capacity experiments, which point to the existence of fractionalized excitations in the spin-liquid state, which in α-RuCl3exists at temperatures just above the onset of magnetic order or at in-plane magnetic fields just beyond the quantum-critical point where antiferromagnetic order becomes suppressed. Thermodynamic and spectroscopic results are compared to theoretical predictions and model calculations. In addition, we document recent progress in elucidating the sub-gap (<1 eV) electronic structure of the 4d5ruthenium electrons to characterize their local electronic configuration. The on-site excitation spectra of thedelectrons below the optical gap can be consistently explained using a spin-orbit coupling constant of ∼170 meV and the concept of multiple spin-orbital excitations. Furthermore, we discuss the phonon spectra of the title compound including rigid-plane shear and compression modes of the single molecular layers. In recent theoretical concepts it has been shown that phonons can couple to Majorana fermions and may play a substantial role in establishing the half-integer thermal quantum Hall effect observed in this material.
Collapse
Affiliation(s)
- A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
- Institute of Applied Physics, Chisinau MD-2028, Moldova
| |
Collapse
|
7
|
Li H, Zhang HK, Wang J, Wu HQ, Gao Y, Qu DW, Liu ZX, Gong SS, Li W. Identification of magnetic interactions and high-field quantum spin liquid in α-RuCl 3. Nat Commun 2021; 12:4007. [PMID: 34188044 PMCID: PMC8242101 DOI: 10.1038/s41467-021-24257-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 06/07/2021] [Indexed: 11/15/2022] Open
Abstract
The frustrated magnet α-RuCl3 constitutes a fascinating quantum material platform that harbors the intriguing Kitaev physics. However, a consensus on its intricate spin interactions and field-induced quantum phases has not been reached yet. Here we exploit multiple state-of-the-art many-body methods and determine the microscopic spin model that quantitatively explains major observations in α-RuCl3, including the zigzag order, double-peak specific heat, magnetic anisotropy, and the characteristic M-star dynamical spin structure, etc. According to our model simulations, the in-plane field drives the system into the polarized phase at about 7 T and a thermal fractionalization occurs at finite temperature, reconciling observations in different experiments. Under out-of-plane fields, the zigzag order is suppressed at 35 T, above which, and below a polarization field of 100 T level, there emerges a field-induced quantum spin liquid. The fractional entropy and algebraic low-temperature specific heat unveil the nature of a gapless spin liquid, which can be explored in high-field measurements on α-RuCl3.
Collapse
Affiliation(s)
- Han Li
- School of Physics, Beihang University, Beijing, China
| | - Hao-Kai Zhang
- School of Physics, Beihang University, Beijing, China
- Institute for Advanced Study, Tsinghua University, Beijing, China
| | - Jiucai Wang
- Institute for Advanced Study, Tsinghua University, Beijing, China
- Department of Physics, Renmin University of China, Beijing, China
| | - Han-Qing Wu
- Center for Neutron Science and Technology, School of Physics, Sun Yat-sen University, Guangzhou, China
| | - Yuan Gao
- School of Physics, Beihang University, Beijing, China
| | - Dai-Wei Qu
- School of Physics, Beihang University, Beijing, China
| | - Zheng-Xin Liu
- Department of Physics, Renmin University of China, Beijing, China.
| | - Shou-Shu Gong
- School of Physics, Beihang University, Beijing, China.
- International Research Institute of Multidisciplinary Science, Beihang University, Beijing, China.
| | - Wei Li
- School of Physics, Beihang University, Beijing, China.
- International Research Institute of Multidisciplinary Science, Beihang University, Beijing, China.
- Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing, China.
| |
Collapse
|
8
|
Pereira RG, Egger R. Electrical Access to Ising Anyons in Kitaev Spin Liquids. PHYSICAL REVIEW LETTERS 2020; 125:227202. [PMID: 33315455 DOI: 10.1103/physrevlett.125.227202] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/03/2020] [Indexed: 06/12/2023]
Abstract
We show that spin-spin correlations in a non-Abelian Kitaev spin liquid are associated with a characteristic inhomogeneous charge density distribution in the vicinity of Z_{2} vortices. This density profile and the corresponding local electric fields are observable, e.g., by means of surface probe techniques. Conversely, by applying bias voltages to several probe tips, one can stabilize Ising anyons (Z_{2} vortices harboring a Majorana zero mode) at designated positions, where we predict a clear Majorana signature in energy absorption spectroscopy.
Collapse
Affiliation(s)
- Rodrigo G Pereira
- International Institute of Physics and Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal, RN, 59078-970, Brazil
| | - Reinhold Egger
- Institut für Theoretische Physik, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
| |
Collapse
|