Theory of Valley-Dependent Transport in Graphene-Based Lateral Quantum Structures
Feng-Wu Chen1*, Mei-Yin Chou2,3,4, Yiing-Rei Chen5, Yu-Shu Wu1,6
1Physics Department, National Tsing-Hua University, Hsin-Chu, Taiwan
2Institute of Atomic and Molecular Science, Academia Sinica, Taipei, Taiwan
3Department of Physics, National Taiwan University, Taipei, Taiwan
4School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30330, USA
5Physics Department, National Taiwan Normal University, Taipei, Taiwan
6Department of Electrical Engineering, National Tsing-Hua University, Hsin-Chu, Taiwan
* presenting author:Feng-Wu Chen,
Electrons in graphene possess an extra degree of freedom ― the valley pseudospin, resembling the ordinary spin in several aspects. Since the first successful exfoliation of graphene from graphite, manipulation of valley pseudospin has drawn much interest from researchers1 and has opened up a new field in device applications known as valleytronics. Theoretically it has been shown2 that controlling the valley pseudospin can be achieved by modulation of electronic states via in-plane, band gap or electrical potential variations in lateral quantum structures. Here, we consider such structures with a single interface where band gap or potential discontinuity take place. Sizable valley contrasts3 between electron transmission or reflection coefficients are well manifested, demonstrating the great potential of such structures as important sources of valley-polarized electrons. Moreover, the magnitudes of valley contrast will be compared between different types of interfaces as well as between bilayer and monolayer graphene systems, and the corresponding underlying mechanisms of valley polarization will be discussed.

[1] Rycerz et al., Nat. Phys. 3, 172 (2007); Xiao et al., Phys. Rev. Lett. 99, 236809 (2007)
[2] Wu et al., Phys. Rev. B 84, 195463 (2011); ibid. B 86, 045456 (2012); ibid. B 88, 125422 (2013).
[3] Chen et al., Phys. Rev. B 94, 075407 (2016).

Keywords: Valleytronics, graphene, lateral quantum structures, Valley-dependent transport, current continuity