High-Order Topological Phase Diagram Revealed by Anomalous Nernst Effect in Janus ScClI Monolayer

TL;DR

This paper reveals the high-order topological phase diagram of the Janus monolayer ScClI, a 2D ferromagnetic material, using the anomalous Nernst effect to identify topological phase transitions and valley polarization effects.

Contribution

It introduces the first complete high-order topological phase diagram for ScClI and links valley polarization with the anomalous Nernst effect to detect topological phases.

Findings

ScClI is a second-order topological insulator.

Valley polarization causes distinct anomalous Nernst conductance in different phases.

The anomalous Nernst effect can reveal topological phase transitions.

Abstract

Higher-order topological properties of two-dimensional(2D) magnetic materials have recently been proposed. In 2D ferromagnetic Janus materials, we find that ScClI is a second-order topological insulator (SOTI). By means of a multi-orbital tight-binding model, we analyze the orbital contributions of higher-order topologies. Further, we give the complete high-order topological phase diagram of ScClI, based on the external field modulation of the magneto-valley coupling and energy levels. 2D ScClI has a pronounced valley polarization, which causes different insulating phases to exhibit completely different anomalous Nernst conductance. As a result, we use the matched anomalous Nernst effect to reveal the topological phase transition process of ScClI. We utilize the characteristics of valley electronics to link higher-order topological materials with the anomalous Nernst effect, which has potential implications for high-order topological insulators and valley electronics.