Orbitally driven giant thermal conductance associated with abnormal strain dependence in hydrogenated graphene-like borophene

Jia He,Chunbao Feng,Dengfeng Li,Chengyong Zhong,Junjie He,Yan Ying,Gang Zhang,Ping Zhou,Hangbo Zhou

doi:10.1038/s41524-019-0183-2

Abstract

Heat energy in solids is carried by phonons and electrons. However, in most two-dimensional (2D) materials, the contribution from electrons to total thermal conduction is much lower than that for phonons. In this work, through first-principles calculations combined with non-equilibrium Green’s function theory, we studied electron and phonon thermal conductance in recently synthesized 2D hydrogen boride. The hexagonal boron network with bridging hydrogen atoms is suggested to exhibit comparable lattice thermal conductance (4.07 nWK−1 nm−2) as graphene (4.1 nWK−1 nm−2), and similar electron thermal conductance (3.6 nWK−1 nm−2), which is almost ten times that of graphene. As a result, total thermal conductance of 2D hydrogen boride is about two-fold of graphene, being the highest value in all known 2D materials. Moreover, tensile strain along the armchair direction leads to an increase in carrier density, significantly increasing electron thermal conductance. The increase in electron thermal conductance offsets the reduction in phonon thermal conductance, contributing to an abnormal increase in thermal conductance. We demonstrate that the high electron density governs extraordinarily high thermal conductance in 2D hydrogen boride, distinctive among 2D materials.

Highlights

Research on atomically thin two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), and black phosphorene is actively pursued due to their remarkable intrinsic properties with great interest in fundamental science and engineering applications.[1]
We demonstrated the coexistence of high phonon and electron thermal conductance in the recently experimentally fabricated 2D hydrogen boride sheet,[27] via a systematic study of electron and phonon quantum transport using first-principles calculation combined with non-equilibrium Green’s function theory
In the following, we focus on the effect of tensile strain on the thermal transport of 2D hydrogen boride

Summary

Introduction

Research on atomically thin two-dimensional (2D) materials such as graphene, transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), and black phosphorene is actively pursued due to their remarkable intrinsic properties with great interest in fundamental science and engineering applications.[1]. To understand the nontrivial strain effect on thermal conductance, we present the phonon transmission along the armchair- or zigzag-direction, as shown in Fig. 3b and Fig. S5. Δσ (ω) identifies the contribution to the change in thermal conductance by phonon mode with frequency ω, with respect to the 8% tensile strain (armchair- or zigzag-strain).

Results

Conclusion