Valley polarization control in WSe2 monolayer by a single-cycle laser pulse

Abstract

Abstract The valley degree of freedom in two-dimensional materials provides an opportunity to extend the functionalities of valleytronics devices. Very short valley lifetimes demand the ultrafast control of valley pseudospin. Here, we theoretically demonstrate the control of valley pseudospin in WSe2 monolayer by single-cycle linearly polarized laser pulse. We use the asymmetric electric field controlled by the carrier-envelope phase (CEP) to make the valley polarization between K and K'-point in the Brillouin zone (BZ). Time-dependent density functional theory with spin-orbit interaction reveals that no valley asymmetry and its CEP dependence is observed within the linear-optical limit. In the nonlinear-optical regime, linearly polarized pulse induces a high degree of valley polarization and this polarization is robust against the field strength. Valley polarization strongly depends and oscillates as a function of CEP. The carrier density distribution forms nodes as the laser intensity increases, our results indicate that the position of the carrier density in the BZ can be controlled by the laser intensity. From the analysis by the massive Dirac Hamiltonian model, the nodes of the carrier density can be attributed to the Landau-Zener-Stückelberg interference of wave packets of the electron wave function.

References in corpus (7)

• Electric Field Effect in Atomically Thin Carbon Films
• Valley polarization in MoS2 monolayers by optical pumping
• Valley Dependent Optoelectronics from Inversion Symmetry Breaking
• k.p theory for two-dimensional transition metal dichalcogenide semiconductors
• Generation and Electric Control of Spin-Coupled Valley Current in WSe2
• Valley Polarization by Spin Injection in a Light-Emitting van der Waals Heterojunction
• Light-Induced Valleytronics in Pristine Graphene

Cited by in corpus (5)

• All-Optical Ultrafast Valley Switching in Two-Dimensional Materials
• Subcycle control of valley-selective excitation via dynamical Franz-Keldysh effect in WSe${}_2$ monolayer
• Enhancement of valley selective excitation by a linearly polarized two-color laser pulse
• Ultrafast Spin Injection in Graphene via Dynamical Carrier Filtering at Transition Metal Dichalcogenide Interfaces
• Ultrafast Optical Control of Multi-Valley States in 2D SnS