arXiv subjects

A. Pustogow

Publications and source records attributed to A. Pustogow.

21 records · Page 2Linked to original sources

arXiv2016

Anions effects on the electronic structure and electrodynamic properties of the Mott insulator $κ$-(BEDT-TTF)$_2$Ag$_2$(CN)$_{3}$

The Mott insulator $κ$-(BEDT-TTF)$_2$Ag$_2$(CN)$_3$ forms a highly-frustrated triangular lattice of $S=1/2$ dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasi-degenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$.

cond-mat.str-el↗

arXiv2016

Lattice vibrations of the charge-transfer salt $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: novel interpretation of the electrodynamic response in a spin-liquid compound

The dimer Mott insulator $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ exhibits unusual electrodynamic properties. Numerical investigations of the electronic ground state and the molecular and lattice vibrations reveal the importance of the Cu$_2$(CN)$_3^-$ anion network coupled to the BEDT-TTF molecules: The threefold cyanide coordination of copper and linkage isomerism in the anion structure cause a loss of symmetry, frustration, disorder, and domain formation. Our findings consistently explain the temperature and polarization-dependent THz and infrared measurements, reinforce the understanding of dielectric properties and have important implications for the quantum spin-liquid state, which should be treated beyond two-dimensional, purely electronic models.

cond-mat.str-el↗

arXiv2014

Low-Energy Excitations in the Quantum Spin-Liquid $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$

The electrodynamic response of the organic spin-liquid candidate $κ$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ has been measured in an extremely wide energy range ($10^{-13}$ to 2 eV) as a function of temperature (5 to 300 K). Below the Mott gap, excitations from the un-gapped spinon continuum cause a considerable contribution to the infrared conductivity, as suggested by the U(1) gauge theory. At THz frequencies we can identify a power-law behavior $σ(ω) \propto ω^β$ with two distinct exponents $β$ that change from 0.9 to 1.3 at low temperatures. The corresponding crossover scales with temperature: $\hbarω_c \approx k_B T$. The observed exponents differ by more than a factor of 2 from the theoretically predicted ones. The findings are compared with those obtained on Herbertsmithites.

cond-mat.str-el↗