Anomalous strain effect on the thermal conductivity of low-buckled two-dimensional silicene.

Bin Ding,Huajian Gao,Gang Zhang,Wuxing Zhou,Xiaoyan Li

doi:10.1093/nsr/nwaa220

Abstract

The thermal conductivity of two-dimensional materials, such as graphene, typically decreases when tensile strain is applied, which softens their phonon modes. Here, we report an anomalous strain effect on the thermal conductivity of monolayer silicene, a representative low-buckled two-dimensional (LB-2D) material. ReaxFF-based molecular dynamics simulations are performed to show that biaxially stretched monolayer silicene exhibits a remarkable increase in thermal conductivity, by as much as 10 times the freestanding value, with increasing applied strain in the range of [0, 0.1], which is attributed to increased contributions from long-wavelength phonons. A further increase in strain in the range of [0.11, 0.18] results in a plateau of the thermal conductivity in an oscillatory manner, governed by a unique dynamic bonding behavior under extreme loading. This anomalous effect reveals new physical insights into the thermal properties of LB-2D materials and may provide some guidelines for designing heat management and energy conversion devices based on such materials.

Highlights

Since the first discovery of graphene, twodimensional (2D) materials have drawn worldwide attention because of their distinguished mechanical, electrical and thermal properties, as well as applications in fields such as nanoelectronic, spintronic, valleytronic, thermoelectric, photovoltaic and optoelectronic devices [1,2,3,4,5]
Reax force field (ReaxFF)-based molecular dynamics simulations are performed to show that biaxially stretched monolayer silicene exhibits a remarkable increase in thermal conductivity, by as much as 10 times the freestanding value, with increasing applied strain in the range of [0, 0.1], which is attributed to increased contributions from long-wavelength phonons
We find that the thermal conductivity of silicene increases within the strain range of [0, 0.1] and saturates to a plateau within the strain range of [0.11, 0.18]

Summary

Introduction

Since the first discovery of graphene, twodimensional (2D) materials have drawn worldwide attention because of their distinguished mechanical, electrical and thermal properties, as well as applications in fields such as nanoelectronic, spintronic, valleytronic, thermoelectric, photovoltaic and optoelectronic devices [1,2,3,4,5]. When the system size is smaller than the phonon de Broglie wavelength, the thermoelectric power factor greatly increases because of the sharper edge of the electron density of states, as theoretically predicted by Hicks and Dresselhaus [6] and recently demonstrated in monolayer InSe [7]. Non-Fourier thermal conductivity was discovered both theoretically and experimentally, resulting from the reduced phonon population and suppressed scattering rate [8,9,10,11]. In 2D materials, phonons are dominant carriers in thermal transport because of the low electron concentration [12]. Phonons play important roles in other physical processes, e.g., phonon–electron coupling can renormalize the electron population and carrier dynamics [13,14]

Methods

Results

Conclusion