应变调控二维材料电子输运性能的机理研究

Owing to the linear dispersion and the ultra-long mean free path with the order of micrometer, the electrons and holes as relativistic Dirac fermions show the ballistic electronic transport phenomenon in clean graphene. And many other two-dimensional materials exhibit many quite similar behaviors. How to control the electronic transport behavior in two-dimensional materials, such as graphene, has aroused a great deal of attention for many researchers. Recently, it was found that the strain has an important effect to tailor the electronic transport in a strain-engineering fashion, where the electronic confinement, collimation and scattering can be achieved by designing an expected substrate-induced local strain profile. For the strain-induced graphene 1D channels, i.e., the quantum waveguide, the bound states and the surface modes occur and play the important role of guided mode on guiding the electrons inside the channel. In addition, a profile of periodic local uniaxial strains or corrugated deformation in graphene can remarkably affect the energy structure, electronic transmission and shot noise by the strain-induced vector potential, scalar potential and renormalized group velocity. In this project, we will focus on the response of the two-dimensional materials, such as graphene, to the in-plane strains and construct a generalized Hamiltonian describing the quasiparticles in a graphene with any in-plane strain. The generalized Hamiltonian is built based on the tight-binding approach and the linear elasticity theory to predict the electronic properties of the in-plane strained two-dimensional materials. The first-principle simulations will be carried out to verify the theoretical modeling. Finally a strain-manipulated electronic transport device based on the two-dimensional material will be fabricated, and a systematic measurement of the strain effects on the electronic transport properties will be conducted.

本项目主要针对应变调控二维材料电子传输性能的机理开展系统的研究工作。基于修正的Tight-Binding方法和弹性变形理论，发展较为通用的解析模型和方法求解复杂面内应变作用下二维材料的能带结构，进而，预报其电子传输特性，重点分析不同的外加应变对传输性能的调控机理和作用。进一步也将利用第一性原理的仿真方法，验证解析模型和方法，并基于二维材料设计一种应变调控电子传输性能原理型器件，利用微纳实验技术实现该器件的制备，并对其性能进行系统测试，验证理论和仿真的结果。我们将重点放在理清不同的二维材料能带结构的共性和个性以及它们的根源；应变调控方法主要适用于哪些二维材料；是否能够发展较为通用的解析模型和方法适用于预报一般二维材料的应变效应。作为一个交叉学科研究课题，研究结果有望强化力学学科对材料科学和现代纳电子器件的发展的引领作用。

本项目聚焦应变与二维材料的光、电和输运等物理性能的耦合机理，及其对具有二维特性的磁性斯格明子、铁电涡畴、准二维光学材料以及拓扑表面态等新结构或物态的影响与调控，开展了系统的理论和实验研究。课题组首先从弹性理论出发，运用密度泛函计算和紧束缚近似方法，建立了变形二维材料的能带结构理论，分析了应变调控电子输运的物理机理；针对典型的二维材料，利用建立的紧束缚哈密顿量并结合Berry相位理论，系统地发展了二维压电材料的微观理论框架；运用泛函分析和晶格波表示，推导了二维磁性斯格明子层展晶格变形的本构方程，建立了层展弹性的理论框架，明晰了应变调控层展晶格物理性质的内在机理；基于相场模拟，分析了利用电致伸缩和剪应变控制二维铁电涡畴翻转，揭示了涡畴形成与翻转的力-电调控机制。实验上，课题组进一步生长出准二维材料EuBiTe3，测试了其光电流和光吸收谱，分析了该材料的力电响应和应变对其光电响应的影响；同时基于质量和能量守恒方程以及流-力关系，模拟了晶体二维表面的生长条纹形成过程，分析了生长界面电动势的规律与条纹分布的内在联系，开展了自动控制减少生长条纹的实验。本项目研究成果为阐明（准）二维材料中力-电（磁）耦合的物理本质做出了实质性的重要贡献，也为此类材料在电子信息科学技术领域的应用提供了创新的起点。相关成果已先后整理成27篇论文发表在物理和力学顶尖及国际知名期刊。