Thermal-transport studies of Two-dimensional Quantum Spin Liquids

Abstract

Quantum spin liquids (QSLs) are fluid-like states of quantum spins where its long-range ordered state is destroyed by quantum fluctuations. The ground state of QSL and its exotic phenomena, which have been extensively discussed for decades, have yet to be identified. We employ thermal transport measurements on newly discovered QSL candidates, $\kappa$-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2, and report that the two organic insulators possess different QSLs characterized by different elementary excitations. In $\kappa$-(BEDT-TTF)2Cu2(CN)3, heat transport is thermally activated at low temperatures, suggesting presence of a spin gap in this QSL. In stark contrast, in EtMe3Sb[Pd(dmit)2]2, a sizable linear temperature dependence of thermal conductivity is clearly resolved in the zero-temperature limit, showing gapless excitation with a long mean free path (~1,000 lattice distances). Such a long mean free path demonstrates a novel feature of QSL as a quantum-condensed state with long-distance coherence.

5 pages, 3 figures; invited mini-review article for ChemPhysChem

References in corpus (7)

• Spin Liquid Ground State of the $S=1/2$ Kagome Heisenberg Model
• U(1) Gauge Theory of the Hubbard Model : Spin Liquid States and Possible Application to k-(BEDT-TTF)_2 Cu_2 (CN)_3
• Quantum Criticality
• Vesignieite BaCu3V2O8(OH)2 as a Candidate Spin-1/2 Kagome Antiferromagnet
• Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Dynamics and transport of the Z_2 spin liquid: application to kappa-(ET)2Cu2(CN)3
• Field-dependent thermal transport in the Haldane chain compound NENP

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• Strongly correlated Fermi systems as a new state of matter
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