ESR studies on the spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: anomalous response below $T=8$ K

TL;DR

This study uses ESR techniques to investigate the low-temperature spin-liquid candidate $-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$, revealing anisotropic relaxation mechanisms and charge inhomogeneities that relate to its unusual quantum properties.

Contribution

It provides new ESR insights into the anisotropic relaxation processes and charge disorder in the spin-liquid candidate, linking microscopic properties to macroscopic behavior.

Findings

Identification of two anisotropic relaxation mechanisms below 8 K

Detection of charge inhomogeneities in copper ions

Comparison of relaxation behavior with other correlated systems

Abstract

The organic conductor $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$ seems to form a quantum spin liquid, although at low temperatures unusual properties are seen in the charge, spin and lattice degrees of freedom. Here we report results of X-band ESR studies of $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$ single crystals as a function of temperature and angle. We find indications of two anisotropic relaxation mechanisms at low temperatures and compare them to the spin-liquid behavior observed in other strongly correlated systems. In addition, we can recognize charge inhomogeneities in the copper ions of the anion layer. This disorder might be linked to the dielectric response measured in this compound.