Field-Induced Carrier Delocalization in the Strain-Induced Mott Insulating State of an Organic Superconductor

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 $\ensuremath{\kappa}\mathrm{\text{\ensuremath{-}}}(\mathrm{BEDT}\mathrm{\text{\ensuremath{-}}}\mathrm{TTF}{)}_{2}\mathrm{Cu}[\mathrm{N}(\mathrm{CN}{)}_{2}]\mathrm{Br}$. Conductivity obeys the formula for an activated transport ${\ensuremath{\sigma}}_{\ensuremath{\square}}={\ensuremath{\sigma}}_{0}\mathrm{exp}(\ensuremath{-}W/{k}_{B}T)$, where ${\ensuremath{\sigma}}_{0}$ is a constant and $W$ depends on the gate voltage. The gate-voltage dependence of the Hall coefficient shows that, unlike in conventional field-effect transistors, the effective mobility of dense hole carriers ($\ensuremath{\sim}1.6\ifmmode\times\else\texttimes\fi{}{10}^{14}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$) 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.