Dynamical Birefringence: Electron-Hole Recollisions as Probes of Berry Curvature

The direct measurement of Berry phases is still a great challenge in condensed-matter systems. The bottleneck has been the ability to adiabatically drive an electron coherently across a large portion of the Brillouin zone in a solid where the scattering is strong and complicated. We break through th...

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Bibliographic Details
Published in:Physical review. X 2017-11, Vol.7 (4), p.041042, Article 041042
Main Authors: Banks, Hunter B., Wu, Qile, Valovcin, Darren C., Mack, Shawn, Gossard, Arthur C., Pfeiffer, Loren, Liu, Ren-Bao, Sherwin, Mark S.
Format: Article
Language:English
Subjects:
Angular momentum
Birefringence
Brillouin zones
Condensed matter physics
Crystal structure
Curvature
Electric fields
Electrons
Harmonic generations
Holes (electron deficiencies)
Infrared lasers
Infrared radiation
Laser beams
Lasers
Phases
Polarization
Semiconductors
Sidebands
Terahertz frequencies
Thin films
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Summary:The direct measurement of Berry phases is still a great challenge in condensed-matter systems. The bottleneck has been the ability to adiabatically drive an electron coherently across a large portion of the Brillouin zone in a solid where the scattering is strong and complicated. We break through this bottleneck and show that high-order sideband generation (HSG) in semiconductors is intimately affected by Berry phases. Electron-hole recollisions and HSG occur when a near-band-gap laser beam excites a semiconductor that is driven by sufficiently strong terahertz-frequency electric fields. We carry out experimental and theoretical studies of HSG from threeGaAs/AlGaAsquantum wells. The observed HSG spectra contain sidebands up to the 90th order, to our knowledge the highest-order optical nonlinearity reported in solids. The highest-order sidebands are associated with electron-hole pairs driven coherently across roughly 10% of the Brillouin zone around theΓpoint. The principal experimental claim is a dynamical birefringence: the intensity and polarization of the sidebands depend on the relative polarization of the exciting near-infrared (NIR) and the THz electric fields, as well as on the relative orientation of the laser fields with the crystal. We explain dynamical birefringence by generalizing the three-step model for high-order harmonic generation. The hole accumulates Berry phases due to variation of its internal state as the quasimomentum changes under the THz field. Dynamical birefringence arises from quantum interference between time-reversed pairs of electron-hole recollision pathways. We propose a method to use dynamical birefringence to measure Berry curvature in solids.
ISSN:2160-3308
2160-3308
DOI:10.1103/PhysRevX.7.041042