Rashba-induced intersubband interference in high-harmonic generation.

Sixth-harmonic high-harmonic generation in BiTeI driven by strong mid-infrared fields shows intensity-scaling kinks and an M-shaped ellipticity dependence linked to Rashba-split band interference.

• Why it matters: High-harmonic spectroscopy can reveal electronic structure and dynamics, but experimental access to interference between spin-orbit-split bands has been elusive.
• What they did: The team measured harmonic yield versus intensity and ellipticity in BiTeI under strong mid-infrared driving, and used simulations attributing the signatures to spin-orbit-mediated multichannel quantum interference from Landau-Zener-Stückelberg-type intersubband tunneling.
• The result: Linearly polarized pulses suppress harmonic yield via destructive interference among electron-hole recombination pathways, while increasing ellipticity changes their relative phase and produces a distinct spectral redshift.

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