Photoexcitation of electron wave packets in quantum spin Hall edge states: effects of chiral anomaly from a localised electric pulse

Abstract

We show that, when a spatially localised electric pulse is applied at the edge of a quantum spin Hall system, electron wavepackets of the helical states can be photoexcited by purely intra-branch electrical transitions, without invoking the bulk states or the magnetic Zeeman coupling. In particular, as long as the electric pulse remains applied, the photoexcited densities lose their character of right- and left-movers, whereas after the ending of the pulse they propagate in opposite directions without dispersion, i.e. maintaining their space profile unaltered. Notably we find that, while the momentum distribution of the photoexcited wave packets depends on the temperature $T$ and the chemical potential $\mu$ of the initial equilibrium state and displays a non-linear behavior on the amplitude of the applied pulse, in the mesoscopic regime the space profile of the wave packets is independent of $T$ and $\mu$. Instead, it depends purely on the applied electric pulse, in a linear manner, as a signature of the chiral anomaly characterising massless Dirac electrons. We also discuss how the photoexcited wave packets can be tailored with the electric pulse parameters, for both low and finite frequencies.

15 pages, 5 figures

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Cited by in corpus (8)

• The chiral anomaly in real space
• All-Electrical Generation of Spin-Polarized Currents in Quantum Spin Hall Insulators
• Levitons in helical liquids with Rashba spin-orbit coupling probed by a superconducting contact
• Interplay between Rashba interaction and electromagnetic field in the edge states of a 2D topological insulator
• Time-resolved measurement of ambipolar edge magnetoplasmon transport in InAs/InGaSb composite quantum wells
• Edge absorption and pure spin current in 2D topological insulator in the Volkov-Pankratov model
• The Dirac paradox in 1+1 dimensions and its realization with spin-orbit coupled nanowires
• Confinement versus interface bound states in spin-orbit coupled nanowires