All-optical valley switch and clock of electronic dephasing

Abstract

2D materials with broken inversion symmetry posses an extra degree of freedom, the valley pseudospin, that labels in which of the two energy-degenerate crystal momenta, K or K', the conducting carriers are located. It has been shown that shining circularly-polarized light allows to achieve close to $100\%$ of valley polarization, opening the way to valley-based transistors. Yet, switching of the valley polarization is still a key challenge for the practical implementation of such devices due to the short coherence lifetimes. Recent progress in ultrashort laser technology now allows to produce trains of attosecond pulses with controlled phase and polarization between the pulses. Taking advantage of such technology, we introduce a coherent control protocol to turn on, off and switch the valley polarization at faster timescales than electronic and valley decoherence, that is, an ultrafast optical valley switch. We theoretically demonstrate the protocol for hBN and MoS${}_2$ monolayers calculated from first principles. Additionally, using two time-delayed linearly-polarized pulses with perpendicular polarization, we show that we can extract the electronic dephasing time $T_2$ from the valley Hall conductivity.

8 pages; 4 figures

References in corpus (2)

• Attosecond dynamics through a Fano resonance: Monitoring the birth of a photoelectron
• Ultrafast Manipulation of Valley Pseudospin

Cited by in corpus (6)

• Roadmap for Photonics with 2D Materials
• All-Optical Ultrafast Valley Switching in Two-Dimensional Materials
• Band nonlinearity-enabled manipulation of Dirac nodes, Weyl cones, and valleytronics with intense linearly polarized light
• Mapping light-dressed Floquet bands by highly nonlinear optical excitations and valley polarization
• Attosecond All-Optical Retrieval of Valley Polarization via Circular Dichroism in Transient Absorption
• Ultrafast Saddletronics