Strain-tunable Dirac semimetal phase transition and emergent superconductivity in a borophane

TL;DR

This study predicts a 2D borophane derivative that exhibits a strain-tunable transition from multiple to a single Dirac cone and demonstrates high-temperature phonon-mediated superconductivity, making it a promising platform for quantum physics research.

Contribution

It introduces a new 2D borophane derivative with tunable Dirac semimetal phases and high-temperature superconductivity based on first-principles calculations.

Findings

Strain induces a transition from three to one Dirac cone.

Superconductivity with a critical temperature of 32.4 K, boosted to 42 K under strain.

Predicted stability and potential for quantum phase transition studies.

Abstract

A two-dimensional (2D) Dirac semimetal with concomitant superconductivity has been long sought but rarely reported. It is believed that light-element materials have the potential to realize this goal owing to their intrinsic lightweight and metallicity. Here, based on the recently synthesized $\beta_{12}$ hydrogenated borophene [Science 371, 1143 (2021)], we investigate its counterpart named $\beta_{12}$-$ \rm {B_5H_3}$. Our first-principles calculations suggest it has good stability. $\beta_{12}$-$ \rm {B_5H_3}$ is a scarce Dirac semimetal demonstrating a strain-tunable phase transition from three Dirac cones to a single Dirac cone. Additionally, $\beta_{12}$-$ \rm {B_5H_3}$ is also a superior phonon-mediated superconductor with a superconducting critical temperature of 32.4 K and can be further boosted to 42 K under external strain. The concurrence of Dirac fermions and superconductivity, supplemented with dual tunabilities, reveals $\beta_{12}$-$ \rm {B_5H_3}$ is an attractive platform to study either quantum phase transition in 2D Dirac semimetal or the superconductivity or the exotic physics brought about by their interplay.