Dissipative Hot-spot Enabled Shock and Bounce Dynamics via Terahertz Quantum Quenches in Helical Edge States

TL;DR

This paper investigates nonlinear wave dynamics in helical edge states of topological insulators under quantum quenches, revealing shock formation and retroreflection phenomena driven by hot spots, with potential terahertz detection.

Contribution

It introduces a novel analysis of hot-spot-induced shock and bounce dynamics in helical liquids during quantum quenches, highlighting nonlinear effects and terahertz emission.

Findings

Shock fronts develop in propagating charge packets.

Opposite charge packets exhibit near-perfect retroreflection.

Terahertz radiation frequency doubling is predicted.

Abstract

We study quantum quenches of helical liquids with spin-flip inelastic scattering. Counterpropagating charge packets in helical edges can be created by an ultrashort electric pulse applied across a 2D topological insulator. Localized "hot spots" that form due to scattering enable two types of strongly nonlinear wave dynamics. First, propagating packets develop self-focusing shock fronts. Second, colliding packets with opposite charge can exhibit near-perfect retroreflection, despite strong dissipation. This leads to frequency doubling that could be detected experimentally from emitted terahertz radiation.