Phonon-Spectrum Narrowing Induced by Ultrafast Charge Fluctuation in an Organic Dimer Mott Insulator

Abstract

We have observed the characteristic temperature dependence of the intermolecular phonon spectrum in the organic dimer Mott insulator kappa-(ET)2Cu2(CN)3 exhibiting a dielectric anomaly at 30 K. The anomalous spectral narrowing of the 55 cm-1 phonon peak at 30 K was analyzed in terms of motional narrowing within the framework of a stationary Gaussian process, i. e., the phonon frequency is modulated by the ultrafast charge fluctuation. The spectral narrowing occurs because the time constant of the correlation time tau_c and the amplitude of the frequency modulation delta satisfy the relation tau_c<delta at 30 K. At temperatures below 30 K, the motional narrowing is disturbed by the increasing of tau_c, near the charge-glass or the short-range order at 6 K. On the other hand, for temperatures above 30 K, the motional narrowing is disturbed by the increase of delta with increasing temperature.

18 pages, 5 figures, accepted Phys. Rev. B

References in corpus (15)

• Electrodynamics of Correlated Electron Materials
• Mott Transition from a Spin Liquid to a Fermi Liquid in the Spin-Frustrated Organic Conductor kappa-(ET)2Cu2(CN)3
• Multiferroicity in an organic charge-transfer salt: Electric-dipole-driven magnetism
• Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Charge order in LuFe2O4: an unlikely route to ferroelectricity
• Absence of charge order in the dimerized κ-phase BEDT-TTF salts
• Dielectric properties of charge ordered LuFe2O4 revisited: The apparent influence of contacts
• Collective excitation of electric dipole on molecular dimer in organic dimer-Mott insulator
• Absence of polar order in LuFe2O4
• Power-law dependence of the optical conductivity observed in the quantum spin-liquid compound κ-(BEDT-TTF)2Cu2(CN)3
• Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator
• Tuning the magnetic dimensionality by charge ordering in the molecular TMTTF salts
• Microscopic phase separation in triangular-lattice quantum spin magnet kappa-(BEDT-TTF)2Cu2(CN)3 probed by muon spin relaxation
• Finite-Temperature Phase Diagram of Quasi-One-Dimensional Molecular Conductors: Quantum Monte Carlo Study
• Collective Charge Excitation in a Dimer Mott Insulating System

Cited by in corpus (2)

• Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)${}_2$Cu${}_2$(CN)${}_3$
• Spectral function of the $J_1-J_2$ Heisenberg model on the triangular lattice