Metal-insulator phase separation in KTaO3-based two-dimensional electron gas

TL;DR

This paper reports a size-dependent metal-insulator transition in KTaO3-based 2DEG caused by phase separation, supported by experiments and theoretical modeling, revealing a new platform for studying electronic phase coexistence.

Contribution

It introduces a novel size-dependent MIT in KTaO3 2DEG and provides a theoretical model for phase separation dynamics, advancing understanding of electronic inhomogeneity.

Findings

Size-dependent MIT observed in micrometer-scale channels

Hysteretic resistance-temperature behavior due to phase competition

Theoretical model simulating phase separation dynamics

Abstract

Electronic phase separation (EPS) originates from an incomplete transformation between electronic phases, causing the inhomogeneous spatial distribution of electronic properties. In the system of two-dimensional electron gas (2DEG), the EPS is usually identified based on a percolative metal-to-superconductor transition. Here, we report a metal-insulator transition (MIT) in KTaO3-based 2DEG with the width of conductive channel decreasing into micrometer scale. Hysteretic resistance-temperature relations are observed due to the competition between metallic and insulating phases, which is tunable by magnetic field. Such a size-dependent MIT effect is attributed to the coexistence and separation of metallic and insulating phases. Combining density functional theory calculation, we propose a theoretical model to simulate the dynamic process of the EPS using the percolation theory, demonstrating the mechanism of size-dependent MIT. Our work suggests a clear and simple 2DEG platform to achieve the spatial coexistence of metallic and insulating phases.