Intense Terahertz Laser Fields Induced and Manipulated Pseudospin Polarization in Graphene

TL;DR

This paper demonstrates how intense terahertz laser fields can induce and control pseudospin polarization in graphene, with potential implications for valleytronics and quantum information processing.

Contribution

It provides an exact solution showing how circularly polarized terahertz fields induce opposite pseudospin polarization in graphene's valleys, and how this polarization can be manipulated.

Findings

Pseudospin polarization can be induced by circularly polarized terahertz fields.

Pseudospin polarization in K and K' valleys have opposite signs under equal electron densities.

Polarization can be controlled by field strength, frequency, and orientation.

Abstract

We investigate the pseudospin-dependent density-energy relation (whose differential with respect to energy is density of states) of a monolayer graphene under intense terahertz laser field by exactly solving the time-dependent Schr\"{o}dinger equation with help of Floquet's theorem. We find that psedospin polarization can be induced by a circular polarized terahertz laser field. The psedospin polarization in K and K$^{\prime}$ valleys can be exactly opposite sign when the electron densities in these two calleys are equivalent. Further more, we find that the psedospin polarization can be manipulated by the strength, frequency, and especially the polarization orientation of the field.