Spectroscopy of Phonon Emission in the Quantum Hall Effect Regime

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Abstract
Phonon emission from two-dimensional electron gases in the quantum Hall effect (QHE) state of a Si MOSFET was measured using the phonon-induced conductivity of the substrate. The inherent phonon energy detection threshold of this system was used to analyze the frequency spectra of the phonons in strong magnetic fields. It was found that phonons with cyclotron energy are emitted in the QHE state. The emission takes place in the corners of the Hall bar sample where the current enters and exits. This observation probably indicates that, in the QHE state, the temperature of the electrons in the corners rises sufficiently to allow inter-Landau-level transitions.