Numerical study of negative nonlocal resistance and backflow current in a ballistic graphene system

发布时间:2021-01-25 浏览量:20

Zibo Wang,1,2 Haiwen Liu,3 Hua Jiang,4,5,* and X. C. Xie6,7,8

1Microsystem and Terahertz Research Center, China

Academy of Engineering Physics, Chengdu 610200, China

2Institute of Electronic Engineering, China

Academy of Engineering Physics, Mianyang 621999, China

3Center for Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China

4School of Physical Science and Technology, Soochow University, Suzhou 215006, China

5Institute for Advanced Study, Soochow University, Suzhou 215006, China

6International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China

7CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing 100190, China

8Beijing Academy of Quantum Information Sciences, West Building 3, No. 10 Xibeiwang East Road, Haidian District, Beijing 100193, China

(Received 6 May 2019; revised manuscript received 17 August 2019; published 21 October 2019)

In addition to the giant peak of the nonlocal resistance RNL, an anomalous negative value of RNL has been observed in graphene systems, although its formation mechanism is not quite understood yet. In this work,utilizing the nonequilibrium Green’s function method, we calculate the local-current flflow in an H-shaped noninteracting graphene system located in a ballistic regime. Similar to the previous conclusions obtained from viscous hydrodynamics, the numerical results show that a local-current vortex appears between the nonlocal measuring terminals, and it induces a backflflow current and a remarkable negative voltage drop at the probe. Specififically, the stronger the vortex is, the more negative RNL becomes. In addition, spin-orbital coupling is added as an additional tool to study this exotic vortex, although this coupling is not a driving force for the arising vortex at all. Moreover, a breakdown of the nonlocal Wiedemann-Franz law is obtained in this ballistic system, and two experimental criteria are provided to confifirm the existence of this exotic vortex. Notably, it is shown that the vortex actually originates from a collision between the flflowing current and the boundaries, due to the long electron mean free path and the resulting ballistic transport caused by the specifific linear spectrum of graphene. DOI: 10.1103/PhysRevB.100.155423