Light-modulated valley-dependent birefringence of electron, the Brewster-like angles, and the giant magnetoresistance-like effect across a graphene-based junction

Abstract

The transmission of electrons in graphene-based p-n and n-p-n junctions on a SiC substrate is investigated. When we irradiate a beam of off-resonant light on a p-n junction, the transmitted angles of electrons from different valleys are unequal, which is similar to the birefringence of light. This is due to the valley polarization induced by the competition between the SiC substrate and the off-resonant light. In addition, a light-modulated fully valley polarized current is realized. In the case of n-p-n junction, we find light-modulated valley-dependent Brewster-like angles at which the electron from one valley is totally transmitted, while the electron from the other valley is totally reflected due to the valley polarization. Furthermore, we propose a new type of tunneling resistance in a graphene-based n-p-n junction irradiated by the off-resonant light. The tunneling resistances have different magnitudes for the different orientations of light and even can show giant magnetoresistance-like effect due to the valley polarization. This is different from the traditional giant magnetoresistance effect in the ferromagnet-insulator-ferromagnet junction, where the spin degree of freedom plays a key role.

Light-modulated electron retroreflection and Klein tunneling in a graphene-based n–p–n junction

“…In fact, graphene, modulated by circularly polarized off-resonant light, has been studied extensively. [12,23,[39][40][41] However, the circularly polarized lightinduced gap can damage the Klein tunneling, which does not meet our expectation. The paper is organized as follows.…”

Anisotropic refraction and valley-spin-dependent anomalous Klein tunneling in a 1T′-MoS2-based p-n junction

“…Traditionally, valley polarization is nonexistent in Dirac materials due to the valley degeneracy and hence the method of applying external fields, e.g., electric field, light illumination, and strain, is an efficient method to generate valley polarization. [41][42][43][44][45][46][47] In this paper, owing to the anisotropic refraction of electron, we find that the valley splitter can be realized in a 1T -MoS 2 -based n-p junction without any external fields.…”