Selective scattering between Floquet-Bloch and Volkov states in a topological insulator

TL;DR

This study uses advanced spectroscopy to explore and control the interaction between Floquet-Bloch and Volkov states in a topological insulator, revealing momentum-dependent coupling and methods to isolate pure states for quantum state engineering.

Contribution

It demonstrates selective control over Floquet-Bloch and Volkov states in a topological insulator using light polarization and electron momentum, advancing coherent light-matter interaction techniques.

Findings

Coupling between states depends on electron momentum.

Light polarization can negate Volkov states.

Pure Floquet-Bloch states can be generated by controlling polarization.

Abstract

The coherent optical manipulation of solids is emerging as a promising way to engineer novel quantum states of matter. The strong time periodic potential of intense laser light can be used to generate hybrid photon-electron states. Interaction of light with Bloch states leads to Floquet-Bloch states which are essential in realizing new photo-induced quantum phases. Similarly, dressing of free electron states near the surface of a solid generates Volkov states which are used to study non-linear optics in atoms and semiconductors. The interaction of these two dynamic states with each other remains an open experimental problem. Here we use Time and Angle Resolved Photoemission Spectroscopy (Tr-ARPES) to selectively study the transition between these two states on the surface of the topological insulator Bi2Se3. We find that the coupling between the two strongly depends on the electron momentum, providing a route to enhance or inhibit it. Moreover, by controlling the light polarization we can negate Volkov states in order to generate pure Floquet-Bloch states. This work establishes a systematic path for the coherent manipulation of solids via light-matter interaction.