Electric control of two-dimensional Van Hove singularity in oxide ultra-thin films

TL;DR

This study demonstrates the electric control of van Hove singularities in atomically thin oxide films, enabling precise tuning of electronic properties and carrier type, which could lead to novel electronic applications.

Contribution

It introduces a method to electrically manipulate 2D van Hove singularities in oxide films, a significant advancement in controlling electronic states in 2D materials.

Findings

Electric fields can precisely tune the 2D VHS.

Charge carrier sign can be controlled via gating.

Potential for enhanced electronic property tuning.

Abstract

Divergent density of states (DOS) can induce extraordinary phenomena such as significant enhancement of superconductivity and unexpected phase transitions. Moreover, van Hove singularities (VHSs) are known to lead to divergent DOS in two-dimensional (2D) systems. Despite the recent interest in VHSs, only a few controllable cases have been reported to date. In this work, we investigate the electronic band structures of a 2D VHS with angle-resolved photoemission spectroscopy and control transport properties by utilizing an atomically ultrathin SrRuO$_3$ film. By applying electric fields with alkali metal deposition and ionic-liquid gating methods, we precisely control the 2D VHS, and the sign of the charge carrier. Use of a tunable 2D VHS in an atomically flat oxide film could serve as a new strategy to realize infinite DOS near the Fermi level, thereby allowing efficient tuning of electric properties.