Non-Fermi-liquid behavior and doping asymmetry in an organic Mott insulator interface

TL;DR

This study investigates the transport properties of an organic Mott insulator under electron and hole doping, revealing universal bad-metal behavior at high temperatures and doping-dependent pseudogap phenomena at lower temperatures.

Contribution

It provides the first detailed comparison of doping asymmetry in transport behaviors of an organic Mott insulator, highlighting universal and material-specific phenomena.

Findings

Bad-metal behavior appears at high temperatures regardless of doping polarity.

Pseudogap behavior is observed only under hole doping at low temperatures.

Fermi-liquid-like behavior is seen under electron doping at low temperatures.

Abstract

High-$T_{\rm C}$ superconductors show anomalous transport properties in their normal states, such as the bad-metal and pseudogap behaviors. To discuss their origins, it is important to speculate whether these behaviors are material-dependent or universal phenomena in the proximity of the Mott transition, by investigating similar but different material systems. An organic Mott transistor is suitable for this purpose owing to the adjacency between the two-dimensional Mott insulating and superconducting states, simple electronic properties, and high doping/bandwidth tunability in the same sample. Here we report the temperature dependence of the transport properties under electron and hole doping in an organic Mott electric-double-layer transistor. At high temperatures, the bad-metal behavior widely appears except at half filling regardless of the doping polarity. At lower temperatures, the pseudogap behavior is observed only under hole doping, while the Fermi-liquid-like behavior is observed under electron doping. The bad-metal behavior seems a universal high-energy scale phenomenon, while the pseudogap behavior is based on lower energy scale physics that can be influenced by details of the band structure.