Power-law dependence of the optical conductivity observed in the quantum spin-liquid compound κ-(BEDT-TTF)2Cu2(CN)3

Abstract

The Mott-insulator κ-(BEDT-TTF)_2Cu_2(CN)_3 is the prime candidate of a quantum spin liquid with puzzling magnetic properties. Our THz and infrared investigations reveal that also the charge dynamics does not follow the expectations for a Mott insulator. The frequency-dependent conductivity exhibits a power-law behavior ${\sigma }_1(\omega )\propto {\omega }^n$ that grows stronger as the temperature decreases and extends all the way through the far-infrared. With $n\approx 0.8$ to 1.5 we obtain a significantly smaller exponent than predicted by Ng and Lee [Phys. Rev. Lett. {\bf 99}, 156402 (2007)]. We suggest fluctuations becomes important in the spin-liquid state and couple to the electrodynamic properties differently compared to the antiferromagnetic Mott insulator κ-(BEDT-TTF)_2Cu[N(CN)_2]Cl. We discuss the various possibilities of how charge fluctuations are influenced by the presence or absence of magnetic order.

arXiv comment7 pages, 8 figures

References in corpus (27)

• The pseudogap in high-temperature superconductors: an experimental survey
• Fermi-liquid instabilities at magnetic quantum phase transitions
• Spin Liquid State in an Organic Mott Insulator with Triangular Lattice
• Mott Transition from a Spin Liquid to a Fermi Liquid in the Spin-Frustrated Organic Conductor kappa-(ET)2Cu2(CN)3
• Quantum frustration in organic Mott insulators: from spin liquids to unconventional superconductors
• Unconventional critical behaviour in a quasi-two-dimensional organic conductor
• Influence of Generic Scale Invariance on Classical and Quantum Phase Transitions
• Multiferroicity in an organic charge-transfer salt: Electric-dipole-driven magnetism
• Transport properties of strongly correlated metals:a dynamical mean-field approach
• Revision of model parameters for kappa-type charge transfer salts: an ab initio study
• Ab initio Derivation of Low-Energy Model for $\kappa$-ET Type Organic Conductors
• Anomalous dielectric response in the dimer Mott insulator $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Theoretical Aspects of Charge Ordering in Molecular Conductors
• Strong electronic correlations in superconducting organic charge transfer salts
• Bandwidth-controlled Mott transition in $\kappa -(BEDT-TTF{)}_{2}Cu[N(CN{)}_2]B{r}_{x}C{l}_{1-x}$ I. Optical studies of localized charge excitations
• Lattice effects and entropy release at the low-temperature phase transition in the spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Mott Transition, Compressibility Divergence and P-T Phase Diagram of Layered Organic Superconductors: An Ultrasonic Investigation
• The Paired Electron Crystal: order from frustration in the quarter-filled band
• Bandwidth-controlled Mott transition in kappa-(BEDT-TTF)2Cu[N(CN)2]Br{x}Cl{1-x}: Optical studies of correlated carriers
• Quasiparticles at the verge of localization near the Mott metal-insulator transition in a two-dimensional material
• Anomalous Lattice Response at the Mott Transition in a Quasi-2D Organic Conductor
• The Paired-Electron Crystal in the Two-Dimensional Frustrated Quarter-Filled Band
• Temperature dependence of structural and electronic properties of the spin-liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3
• Power-law Conductivity inside the Mott gap: application to $\kappa -(BEDT-TTF{)}_{2}C{u}_2(CN{)}_3$
• Electronic properties of correlated metals in the vicinity of a charge order transition: optical spectroscopy of $\alpha$-(BEDT-TTF)${}_{2}M$Hg(SCN)${}_4$ ($M$ = NH${}_4$, Rb, Tl)
• Spin diffusion and magnetic eigenoscillations confined to single molecular layers in the organic conductors kappa-(BEDT-TTF)_2Cu[N(CN)_2X (X=Cl, Br)
• Beyond the quantum spin liquid concept in frustrated two dimensional organic superconductors

Cited by in corpus (28)

• Quantum Spin Liquids
• Quantum Spin Liquid States
• Holographic quantum matter
• Absence of charge order in the dimerized κ-phase BEDT-TTF salts
• Pressure-Tuned Exchange Coupling of a Quantum Spin Liquid in the Molecular Triangular Lattice $\kappa$-(ET)${}_2$Ag${}_2$(CN)${}_3$
• Spin Induced Optical Conductivity in the Spin Liquid Candidate Herbertsmithite
• Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Lattice vibrations of the charge-transfer salt $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$: novel interpretation of the electrodynamic response in a spin-liquid compound
• Mechanisms for Sub-Gap Optical Conductivity in Herbertsmithite
• Dielectric Spectroscopy on Organic Charge-Transfer Salts
• Spectral function of the $J_1-J_2$ Heisenberg model on the triangular lattice
• Critical Behavior in Doping-Driven Metal$-$Insulator Transition on Single-Crystalline Organic Mott-FET
• Mechanism for subgap optical conductivity in honeycomb Kitaev materials
• Electrodynamics of quantum spin liquids
• Theory of electronic magnetoelectric coupling in $d^5$ Mott insulators
• Site-specific ${}^{13}$C NMR study on locally distorted triangular lattice of organic conductor $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Dynamical reduction of the dimensionality of exchange interactions and the "spin-liquid" phase of $\kappa$-(BEDT-TTF)${}_{2}X$
• Low-Energy Excitations in Quantum Spin-Liquids Identified by Optical Spectroscopy
• ESR studies on the spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$: anomalous response below $T=8$ K
• Taking a critical look at holographic critical matter
• Phonon-Spectrum Narrowing Induced by Ultrafast Charge Fluctuation in an Organic Dimer Mott Insulator
• The magneto-optical Faraday effect in spin liquid candidates
• Novel Dipole-Lattice coupling in the Quantum-Spin-Liquid Material $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Optical conductivity and surface plasmon modes of U(1) spin liquid states with large spinon Fermi surfaces
• Charge localization in strongly correlated $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]I due to inherent disorder
• Photoinduced Frustration Modulation in $\kappa$-type Quantum Spin Liquid Candidates
• Gapped magnetic ground state in the spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Ag${}_2$(CN)${}_3$ suggested by magnetic spectroscopy