2D Ladder polyborane: an ideal Dirac semimetal with a multi-feld-tunable band gap

TL;DR

This paper introduces 2D ladder polyborane, a hydrogenated boron sheet with a Dirac semimetallic nature, tunable band gaps via external fields, and potential for advanced electronic applications.

Contribution

It presents a novel hydrogenated boron sheet with stable Dirac semimetal properties and multi-field tunability, advancing 2D material design and topological electronic states.

Findings

Achieves a stable, anisotropic Dirac cone in 2D ladder polyborane.

Demonstrates external field control over Dirac fermions and topological domain walls.

Provides a minimal tight-binding model for the material's electronic structure.

Abstract

Hydrogen, a simple and magic element, has attracted increasing attention for its effective incorporation within solids and powerful manipulation of electronic states. Here, we show that hydrogenation tackles common problems in two-dimensional borophene, e.g., stability and applicability. As a prominent example, a ladder-like boron hydride sheet, named as 2D ladder polyborane, achieves the desired outcome, enjoying the cleanest scenario with an anisotropic and tilted Dirac cone, that can be fully depicted by a minimal two-band tight-binding model. Introducing external fields, such as an electric field or a circularly-polarized light field can effectively induce distinctive massive Dirac fermions, whereupon four types of multi-field-driven topological domain walls hosting tunable chirality and valley indexes are further established. Moreover, the 2D ladder polyborane is thermodynamically stable at room temperature and supports highly switchable Dirac fermions, providing an ideal platform for realizing and exploring the various multi-field-tunable electronic states.