Ultrafast optical control over spin and momentum in solids

TL;DR

This paper demonstrates a method for ultrafast optical control of spin and momentum in solids, specifically in monolayer WSe2, using hybrid laser pulses to precisely manipulate electronic states in reciprocal space.

Contribution

It introduces a novel approach employing hybrid laser pulses to achieve targeted control over spin and momentum in 2D semiconductors at femtosecond timescales.

Findings

Controlled creation of spin- and momentum-specific charge in the Brillouin zone.

Demonstration of simultaneous intraband and interband excitations.

Potential for ultrafast preparation of excited states with specified momenta.

Abstract

The coupling of laser light to matter can exert sub-cycle coherent control over material properties, with optically induced currents and magnetism shown to be controllable on ultrafast femtosecond time scales. Here, by employing laser light consisting of both linear and circular pulses, we show that charge of specified spin and crystal momentum can be created with precision throughout the first Brillouin zone. Our hybrid pulses induce in a controlled way both adiabatic intraband motion as well as vertical interband excitation between valence and conduction bands, and require only a gapped spin split valley structure for their implementation. This scenario is commonly found in the 2d semi-conductors, and we demonstrate our approach with monolayer WSe$_2$. We thus establish a route from laser light to local control over excitations in reciprocal space, opening the way to the preparation of momenta specified excited states at ultrafast time scales.