Kitaev exchange and field-induced quantum spin-liquid states in honeycomb α-RuCl3

The exotic properties of quantum spin liquids (QSLs) have continually been of interest since Anderson’s 1973 ground-breaking idea. Geometrical frustration, quantum fluctuations, and low dimensionality are the most often evoked material’s characteristics that favor the long-range fluctuating spin state without freezing into an ordered magnet or a spin glass at low temperatures. Among the few known QSL candidates, organic crystals have the advantage of having rich chemistry capable of finely tuning their microscopic parameters. Here, we demonstrate the emergence of a QSL state in [EDT-TTF-CONH2]2+[BABCO−] (EDT-BCO), where the EDT molecules with spin-1/2 on a triangular lattice form layers which are separated by a sublattice of BCO molecular rotors. By several magnetic measurements, we show that the subtle random potential of frozen BCO Brownian rotors suppresses magnetic order down to the lowest temperatures. Our study identifies the relevance of disorder in the stabilization of QSLs.

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Discovery of an ultra-quantum spin liquid

10.21203/rs.3.rs-351743/v1 ◽

2021 ◽

Author(s):

Yanxing Yang ◽

Cheng Tan ◽

Zihao Zhu ◽

J. Zhang ◽

Zhaofeng Ding ◽

...

Keyword(s):

Specific Heat ◽

Quantum Fluctuations ◽

Quantum Spin ◽

Spin Liquid ◽

Singlet Ground State ◽

Relaxation Rates ◽

Scale Invariant ◽

Liquid States ◽

Increasing Temperature ◽

Quantum Spin Liquid

Abstract Quantum fluctuations are expected to lead to highly entangled spin-liquid states in some two-dimensional spin-1/2 compounds. We have synthesized and measured thermodynamic properties and muon relaxation rates in two related such compounds, one of which is the least disordered of this kind synthesized hitherto and reveals intrinsic properties of a class of spin-liquids. Its measured properties can all be simply characterized by scale invariant time-dependent fluctuations with a single parameter. The specific heat divided by temperature and muon relaxation rates are both temperature independent at low temperatures, followed by a logarithmic decrease with increasing temperature. Even more remarkably, ∼57% of the magnetic entropy is missing down to temperatures of O(10−3) the exchange energy, independent of magnetic field up to gµBH > kBT . This is evidence that quantum fluctuations lead either to a gigantic specific heat peak from topological singlet excitations below such temperatures, or to an extensively degenerate topological singlet ground state. These results reveal an ultra-quantum state of matter.

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Quantum spin liquid states

Reviews of Modern Physics ◽

10.1103/revmodphys.89.025003 ◽

2017 ◽

Vol 89 (2) ◽

Cited By ~ 351

Author(s):

Yi Zhou ◽

Kazushi Kanoda ◽

Tai-Kai Ng

Keyword(s):

Quantum Spin ◽

Spin Liquid ◽

Liquid States ◽

Quantum Spin Liquid

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Spin Liquid versus Spin Orbit Coupling on the Triangular Lattice

SciPost Physics ◽

10.21468/scipostphys.4.1.003 ◽

2018 ◽

Vol 4 (1) ◽

Cited By ~ 22

Author(s):

Jason Iaconis ◽

Chunxiao Liu ◽

Gábor Halász ◽

Leon Balents

Keyword(s):

Triangular Lattice ◽

Quantum Spin ◽

Orbit Coupling ◽

Spin Liquid ◽

Spin Orbit Coupling ◽

Spin Orbit ◽

Liquid States ◽

Quantum Spin Liquid ◽

The Relationship ◽

Liquid Physics

In this paper, we explore the relationship between strong spin-orbit coupling and spin liquid physics. We study a very general model on the triangular lattice where spin-orbit coupling leads to the presence of highly anisotropic interactions. We use variational Monte Carlo to study both U(1)U(1) quantum spin liquid states and ordered ones, via the Gutzwiller projected fermion construction. We thereby obtain the ground state phase diagram in this phase space. We furthermore consider effects beyond the Gutzwiller wavefunctions for the spinon Fermi surface quantum spin liquid, which are of particular importance when spin-orbit coupling is present.

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A possible quantum spin liquid in a spin-orbital entangled 2d magnet

10.36471/jccm_november_2017_02 ◽

2017 ◽

Keyword(s):

Quantum Spin ◽

Spin Liquid ◽

Spin Orbital ◽

Quantum Spin Liquid

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Correlation holes and slow dynamics induced by fractional statistics in gapped quantum spin liquids

Nature Communications ◽

10.1038/s41467-021-21495-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Oliver Hart ◽

Yuan Wan ◽

Claudio Castelnovo

Keyword(s):

Transport Properties ◽

Realistic Model ◽

Feedback Mechanism ◽

Quantum Spin ◽

Spin Liquid ◽

Spin Liquids ◽

Slow Dynamics ◽

Temperature Dependent ◽

Quantum Spin Liquids ◽

Quantum Spin Liquid

AbstractRealistic model Hamiltonians for quantum spin liquids frequently exhibit a large separation of energy scales between their elementary excitations. At intermediate, experimentally relevant temperatures, some excitations are sparse and hop coherently, whereas others are thermally incoherent and dense. Here, we study the interplay of two such species of quasiparticle, dubbed spinons and visons, which are subject to nontrivial mutual statistics – one of the hallmarks of quantum spin liquid behaviour. Our results for $${{\mathbb{Z}}}_{2}$$ Z 2 quantum spin liquids show an intriguing feedback mechanism, akin to the Nagaoka effect, whereby spinons become localised on temperature-dependent patches of expelled visons. This phenomenon has important consequences for the thermodynamic and transport properties of the system, as well as for its response to quenches in temperature. We argue that these effects can be measured in experiments and may provide viable avenues for obtaining signatures of quantum spin liquid behaviour.

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Gapless Quantum Spin Liquid in the Triangular System Sr3CuSb2O9

Physical Review Letters ◽

10.1103/physrevlett.125.267202 ◽

2020 ◽

Vol 125 (26) ◽

Author(s):

S. Kundu ◽

Aga Shahee ◽

Atasi Chakraborty ◽

K. M. Ranjith ◽

B. Koo ◽

...

Keyword(s):

Quantum Spin ◽

Spin Liquid ◽

Triangular System ◽

Quantum Spin Liquid

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Giant phonon anomalies in the proximate Kitaev quantum spin liquid α-RuCl3

Nature Communications ◽

10.1038/s41467-021-23826-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Haoxiang Li ◽

T. T. Zhang ◽

A. Said ◽

G. Fabbris ◽

D. G. Mazzone ◽

...

Keyword(s):

Acoustic Phonon ◽

Energy Scale ◽

Quantum Spin ◽

Majorana Fermion ◽

Spin Liquid ◽

Optical Phonons ◽

Large Intensity ◽

Topological Quantum ◽

Topological State ◽

Quantum Spin Liquid

AbstractThe Kitaev quantum spin liquid epitomizes an entangled topological state, for which two flavors of fractionalized low-energy excitations are predicted: the itinerant Majorana fermion and the Z2 gauge flux. It was proposed recently that fingerprints of fractional excitations are encoded in the phonon spectra of Kitaev quantum spin liquids through a novel fractional-excitation-phonon coupling. Here, we detect anomalous phonon effects in α-RuCl3 using inelastic X-ray scattering with meV resolution. At high temperature, we discover interlaced optical phonons intercepting a transverse acoustic phonon between 3 and 7 meV. Upon decreasing temperature, the optical phonons display a large intensity enhancement near the Kitaev energy, JK~8 meV, that coincides with a giant acoustic phonon softening near the Z2 gauge flux energy scale. These phonon anomalies signify the coupling of phonon and Kitaev magnetic excitations in α-RuCl3 and demonstrates a proof-of-principle method to detect anomalous excitations in topological quantum materials.

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