Abstract

Graphene, a special two-dimensional material, has a unique band structure that allows the type and concentration of carriers to be controlled through a gate voltage, and it has potential applications in bipolar nanoelectronic devices. In this paper, based on the tight-binding model of graphene p-n junctions, by using the nonequilibrium Green’s function method and Landauer-Büttiker formula, the thermal dissipation of electric transport in graphene p-n junctions in a magnetic field is investigated. Under a strong magnetic field, both sides of the junction are in the quantum Hall regime, thus the topologically protected chiral edge states appear. Intuitively, the topologically protected chiral edge states are dissipationless. However, the results show that thermal dissipation can occur in the quantum Hall regime in graphene junctions in the presence of dissipation sources, although the topologically protected chiral edge states still exist. In clean graphene junctions, thermal dissipation occurs mainly at the edge for the unipolar transport, but it occurs both at the edge and at the interface of the junctions for the bipolar transport. In the presence of disorder, thermal dissipation is significantly enhanced both in the unipolar junction and in the bipolar junction, and it increases with disorder strength increasing. Besides, the energy distribution of electrons at different positions is also studied, which shows that the thermal dissipation always occurs as long as the energy distribution is in nonequilibrium. This indicates that the topology can protect only the propagation direction of electrons, but it can not suppress the occurrence of thermal dissipation.

Highlights

  • The results show that thermal dissipation can occur in the quantum Hall regime in graphene junctions in the presence of dissipation sources, although the topologically protected chiral edge states still exist

  • 偶 极结输运时, 结的界面上会同时存在来自于左右端 口的载流子, 因此结界面上的电子处于非平衡分 布, 导致热耗散在结的界面上发生; 如果填充因子 较大, 热耗散还可以在体系的边缘上发生

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Summary

Introduction

石墨烯莫尔超晶格体系的拓扑性质及光学研究进展 Topological properties of graphene moiré superlattice systems and recent optical studies 物理学报. 声子系统中弹性波与热输运的拓扑与非互易现象 Topological and non-reciprocal phenomena in elastic waves and heat transport of phononic systems 物理学报. HgTe/CdTe量子阱中自旋拓扑态的退相干效应 Dephasing effect of quantum spin topological states in HgTe/CdTe quantum well 物理学报. 本文基于紧束缚格点模型, 利用非平衡格林函数方 法及 Landauer-Büttiker 公式, 研究了石墨烯 p-n 结在磁场中的电输运热耗散问题. 关键词:石墨烯 p-n 结, 热耗散, 量子输运, 拓扑 PACS:72.80.Vp, 73.20.–r, 73.23.Ad, 81.05.ue

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