Field-induced carrier delocalization in the strain-induced Mott insulating state of an organic superconductor

TL;DR

This study investigates how an electric field influences carrier behavior in a strain-induced Mott insulator of an organic superconductor, revealing field-induced delocalization of carriers and changes in conductivity and mobility.

Contribution

It demonstrates that gate voltage can delocalize carriers in a Mott insulator, altering its electronic properties, which is a novel insight into field effects in correlated electron systems.

Findings

Conductivity follows activated transport with gate-dependent activation energy.

Effective mobility of hole carriers increases with positive gate voltage.

Carrier delocalization is driven by the electric field, not just doping.

Abstract

We report the influence of the field effect on the dc resistance and Hall coefficient in the strain-induced Mott insulating state of an organic superconductor $\kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br. Conductivity obeys the formula for activated transport $\sigma_{\Box} = \sigma_{0}\exp(-W/k_{B}T)$, where $\sigma_{0}$ is a constant and $W$ depends on the gate voltage. The gate voltage dependence of the Hall coefficient shows that, unlike in conventional FETs, the effective mobility of dense hole carriers ($\sim1.6\times 10^{14}$ cm$^{-2}$) is enhanced by a positive gate voltage. This implies that carrier doping involves delocalization of intrinsic carriers that were initially localized due to electron correlation.