A theory proposal for extracting non-equilibrium dephasing rates from a terahertz Bloch wave interferometer in bulk GaAs

Understanding dephasing mechanisms is important in the study of interactions between quasi-particles and manipulation of quantum coherences in solids. Of special interest are the dephasing mechanisms for driven systems far away from thermal equilibrium such as semiconductors in the condition of high-order sideband generation (HSG). HSG occur in a near-resonantly excited semiconductor that is driven by a sufficiently strong, terahertz (THz)-frequency electric field. Dephasing rates are key ingredients in determining the strengths and polarizations of the THz sidebands. For HSG in bulk GaAs, dynamical birefringence results from quantum interference of the spin-3/2 hole Bloch wave functions, such that ellipticity in the sidebands can arise from linearly polarized driven fields. The information about the hole quasi-particles, including their effective masses, pseudo-spins, and dephasing rates, is then coded in the sideband polarizations. We show that THz-driven materials such as bulk GaAs can be used as an interferometer of Bloch waves to extract dephasing rates of the electron-hole pairs in strong driving fields. Our work provides a way to explore non-equilibrium dephasing mechanisms in semiconductors and a principle for coherently controlling THz sideband emission.