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Kawamura H, Uematsu K. Nature of the randomness-induced quantum spin liquids in two dimensions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:504003. [PMID: 31470422 DOI: 10.1088/1361-648x/ab400c] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The nature of the randomness-induced quantum spin liquid state, the random-singlet state, is investigated in two dimensions (2D) by means of the exact-diagonalization and the Hams-de Raedt methods for several frustrated lattices, e.g. the triangular, the kagome and the J 1-J 2 square lattices. Properties of the ground state, the low-energy excitations and the finite-temperature thermodynamic quantities are investigated. The ground state and the low-lying excited states consist of nearly isolated singlet-dimers, clusters of resonating singlet-dimers, and orphan spins. Low-energy excitations are either singlet-to-triplet excitations, diffusion of orphan spins accompanied by the recombination of nearby singlet-dimers, creation or destruction of resonating singlet-dimers clusters. The latter two excitations give enhanced dynamical 'liquid-like' features to the 2D random-singlet state. Comparison is made with the random-singlet state in a 1D chain without frustration, the similarity and the difference between in 1D and in 2D being highlighted. Frustration in a wide sense, not only the geometrical one but also including the one arising from the competition between distinct types of interactions, play an essential role in stabilizing this frustrated random singlet state. Recent experimental situations on both organic and inorganic materials are reviewed and discussed.
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Affiliation(s)
- Hikaru Kawamura
- Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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Fujiyama S, Kato R. Fragmented Electronic Spins with Quantum Fluctuations in Organic Mott Insulators Near a Quantum Spin Liquid. PHYSICAL REVIEW LETTERS 2019; 122:147204. [PMID: 31050449 DOI: 10.1103/physrevlett.122.147204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Indexed: 06/09/2023]
Abstract
Magnetic structures of organic Mott insulators X[Pd(dmit)_{2}]_{2} (X=Me_{4}P, Me_{4}Sb), of which electronic states are located near a quantum spin liquid (X=EtMe_{3}Sb), are demonstrated by ^{13}C nuclear magnetic resonance. Antiferromagnetic spectra and nuclear relaxations show two distinct magnetic moments within each Pd(dmit)_{2} molecule, which cannot be described by single band dimer-Mott model and requires intramolecular electronic correlation. This unconventional fragmentation of S=1/2 electron spin with strong quantum fluctuation is presumably caused by nearly degenerated intramolecular multiple orbitals, and shares a notion of quantum liquids where electronic excitations are fractionalized and S=1/2 spin is no longer an elementary particle.
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Affiliation(s)
- S Fujiyama
- RIKEN, Condensed Molecular Materials Laboratory, Wako 351-0198, Japan
| | - R Kato
- RIKEN, Condensed Molecular Materials Laboratory, Wako 351-0198, Japan
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Pustogow A, Saito Y, Zhukova E, Gorshunov B, Kato R, Lee TH, Fratini S, Dobrosavljević V, Dressel M. Low-Energy Excitations in Quantum Spin Liquids Identified by Optical Spectroscopy. PHYSICAL REVIEW LETTERS 2018; 121:056402. [PMID: 30118313 DOI: 10.1103/physrevlett.121.056402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Indexed: 06/08/2023]
Abstract
The electrodynamic response of organic spin liquids with highly frustrated triangular lattices has been measured in a wide energy range. While the overall optical spectra of these Mott insulators are governed by transitions between the Hubbard bands, distinct in-gap excitations can be identified at low temperatures and frequencies, which we attribute to the quantum-spin-liquid state. For the strongly correlated β^{'}-EtMe_{3}Sb[Pd(dmit)_{2}]_{2}, we discover enhanced conductivity below 175 cm^{-1}, comparable to the energy of the magnetic coupling J≈250 K. For ω→0, these low-frequency excitations vanish faster than the charge-carrier response subject to Mott-Hubbard correlations, resulting in a dome-shaped band peaked at 100 cm^{-1}. Possible relations to spinons, magnons, and disorder are discussed.
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Affiliation(s)
- A Pustogow
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
| | - Y Saito
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
- Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
| | - E Zhukova
- Moscow Institute of Physics and Technology (State University), 141700, Dolgoprudny, Moscow Region, Russia
| | - B Gorshunov
- Moscow Institute of Physics and Technology (State University), 141700, Dolgoprudny, Moscow Region, Russia
| | - R Kato
- Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - T-H Lee
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
| | - S Fratini
- Institut Néel-CNRS and Université Grenoble Alpes, 38042 Grenoble Cedex 9, France
| | - V Dobrosavljević
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, USA
| | - M Dressel
- 1. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany
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Temperature Dependence of Crystal Structures and Band Parameters in Quantum Spin Liquid β′-EtMe3Sb[Pd(dmit)2]2 and Related Materials. CRYSTALS 2018. [DOI: 10.3390/cryst8030138] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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