Effective-Hamiltonian reconstruction through Bloch-wave interferometry in bulk GaAs driven by strong THz fields

TL;DR

This study reconstructs an effective Hamiltonian of bulk GaAs using high-order sideband generation data and Bloch-wave interferometry, revealing insights into bandgap, effective masses, and dephasing under strong THz fields.

Contribution

It introduces a method combining HSG measurements with Bloch-wave interferometry to directly determine key Hamiltonian parameters in bulk GaAs.

Findings

Effective Hamiltonian parameters for GaAs are unambiguously determined.

The GaAs bandgap is found to be about 10 meV larger than previous estimates.

Strong THz fields can suppress optical-phonon emission energy threshold.

Abstract

Reconstructing effective Hamiltonians of condensed matter systems directly from experimental data is challenging because of the intricate relationship between Hamiltonian parameters and observables. Here, we reconstruct an effective three-band electron-hole (e-h) Hamiltonian in bulk GaAs based on high-order sideband generation (HSG) induced by quasi-continuous NIR and THz lasers. We perform polarimetry of high-order sidebands while varying the wavelength and polarization of the NIR laser, as well as the strength of the THz field. An analytic model is derived to incorporate the effects of both dephasing and quantum fluctuations around the semiclassical e-h recollision pathways. Surprisingly, the contribution of quantum fluctuations to the decay of sideband intensity with increasing sideband order is comparable to the contribution of dephasing. We simultaneously and unambiguously determine through Bloch-wave interferometry the effective Hamiltonian parameter that determines the e-h reduced masses, the bandgap of GaAs, and two dephasing constants associated with two e-h species. We demonstrate that full Hamiltonian reconstruction can be achieved by combining HSG measurements with absorbance spectroscopy. Unexpectedly, we find that the extracted bandgap of GaAs is about 10 meV larger than the value inferred from previous absorbance measurements. Quantum-kinetic analysis suggests that, in the HSG experiments, the e-h energy may be renormalized through Fr\"ohlich interaction that is modulated by the strong THz fields. We also show that the energy threshold for optical-phonon emission can be suppressed by applying a strong THz field, leading to nearly constant dephasing rates.