Abstract
It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.
Highlights
The electron-phonon (e-ph) interaction at the interface of supported thin films plays an important role in the electronic transport
In this paper we demonstrate that Brillouin light scattering (BLS) from single surface phonons can be used to investigate mode-selected e-ph interactions in the GHz domain at the interface of a TI topological insulator thin film epitaxially grown on a semiconductor substrate
The same holds true for the longitudinal acoustic resonance (LR)[23] and the lowest-order Sezawa waves (SWs), which occur in the film which is deposited on a stiffer substrate[24,25]
Summary
The electron-phonon (e-ph) interaction at the interface of supported thin films plays an important role in the electronic transport. In a BLS experiment on a supported film, the RW frequency can be tuned so that the penetration depths matches the film thickness At this frequency the phonon strain field and the associated e-ph deformation potential have their maxima just in the space charge region along the interface. The observation of a comparatively large softening of the phonon frequencies around the wavevector fulfilling such tuning conditions allows to measure the e-ph coupling of the interface electronic states with the phonon modes having the given wavevector. The latter can in turn be changed by changing the film thickess, so that the observed anomalies in the dispersion curves may be termed as structural anomalies
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