# Critical Behavior in Doping-Driven Metal$-$Insulator Transition on Single-Crystalline Organic Mott-FET

## TL;DR

This study investigates the continuous doping-driven metal-insulator transition in a single-crystalline organic Mott insulator using FETs, revealing a high-temperature Mott quantum critical crossover distinct from traditional bad metal behavior.

## Contribution

It provides the first detailed transport analysis of a doping-driven MIT in a 2D organic Mott insulator, highlighting a quantum critical crossover and contrasting with inorganic Mott insulators.

## Key findings

- Conductivity crossover occurs around the conductance quantum e^2/h.
- Transition involves two-step crossovers in Hall and conductivity measurements.
- Transport near the MIT is described by a high-temperature Mott quantum critical crossover.

## Abstract

We present the carrier transport properties in the vicinity of a doping-driven Mott transition observed at a field-effect transistor (FET) channel using a single crystal of the typical two-dimensional organic Mott insulator $\kappa$-(BEDT-TTF)$_2$CuN(CN)$_2$Cl ($\kappa$-Cl).The FET shows a continuous metal$-$insulator transition (MIT) as electrostatic doping proceeds. The phase transition appears to involve two-step crossovers, one in Hall measurement and the other in conductivity measurement. The crossover in conductivity occurs around the conductance quantum $e^2/h$ , and hence is not associated with "bad metal" behavior, which is in stark contrast to the MIT in half-filled organic Mott insulators or that in doped inorganic Mott insulators. Through in-depth scaling analysis of the conductivity, it is found that the above carrier transport properties in the vicinity of the MIT can be described by a high-temperature Mott quantum critical crossover, which is theoretically argued to be a ubiquitous feature of various types of Mott transitions. [This document is the unedited Authors' version of a Submitted Work that was subsequently accepted for publication in Nano Letters, copyright \copyright American Chemical Society after peer review. To access the final edited and published work see http://dx.doi.org/10.1021/acs.nanolett.6b03817]