Superinsulating behavior in granular Pb film on gated few-layer MoS$_2$

TL;DR

This study demonstrates super-insulating behavior in a granular Pb film on gated MoS$_2$, revealing a threshold voltage and magnetic field effects that suggest a complex interplay of thermal activation and quantum fluctuations.

Contribution

It introduces a novel super-insulating state in a granular Pb film on MoS$_2$, with detailed analysis of threshold voltage and magnetic field effects, highlighting the role of quantum fluctuations.

Findings

Super-insulating behavior observed below T_C≈7K.

Threshold voltage varies with gate voltage.

Insulating state suppressed above a critical magnetic field.

Abstract

We report a super-insulating behavior, in a device having granular Pb film on back-gated few-layer $\mathrm{MoS_2}$, below an onset temperature same as the critical temperature $T_{\rm C}\approx7$ K of bulk Pb. Below $T_{\rm C}$, the current-voltage characteristics exhibit a threshold voltage marking a crossover between the low-bias insulating and the high-bias normal-resistance states, consistent with the known super-insulating state behavior. A temperature dependent critical magnetic field is also found above which the insulating behavior is suppressed. The threshold voltage is found to vary with the gate-voltage but the critical field remains unchanged. With reducing temperature, the sample conductance saturates to a finite value, which depends on magnetic field and gate-voltage. This saturation behavior is found to be inconsistent with the charge-BKT and the thermal activation models but it can be fitted well to a combination of thermal activation and quantum fluctuations.