Role of strain on the coherent properties of GaAs excitons and biexcitons

Abstract

Polarization-dependent two-dimensional Fourier-transform spectroscopy (2DFTS) is performed on excitons in strained bulk GaAs layers, probing the coherent response for differing amounts of strain. Biaxial tensile strain lifts the degeneracy of heavy-hole (HH) and light-hole (LH) valence states, leading to an observed splitting of the associated excitons at low temperature. Increasing the strain increases the magnitude of the HH/LH exciton peak splitting, induces an asymmetry in the off-diagonal interaction coherences, increases the difference in the HH and LH exciton homogenous linewidths, and increases the inhomogeneous broadening of both exciton species. All results arise from strain-induced variations in the local electronic environment, which is not uniform along the growth direction of the thin layers. For cross-linear polarized excitation, wherein excitonic signals give way to biexcitonic signals, the high-strain sample shows evidence of bound LH, HH, and mixed biexcitons.

Signatures of four-particle correlations associated with exciton-carrier interactions in coherent spectroscopy on bulk GaAs

“…The sample exhibits two peaks at 1.5100 eV and 1.5125 eV, corresponding to the light-hole and heavy-hole exciton resonances, respectively. Due to differing thermal expansion coefficients of GaAs and the sapphire substrate, which were bonded at room temperature, biaxial tensile strain is produced in the GaAs layer at low temperature, lifting the degeneracy of the valence bands 44,45 .…”

Coordination Mechanism in Dopamine Neurons of the <em>Substantia Nigra Pars Compacta</em> and Norepinephrine Neurons of the <em>Locus Coeruleus</em>

“…The combination of such strain/stress field vectors has thus been demonstrated to result in controllable generation of quantum mechanical effects, even where the dimensional characteristics of the QDs are not matched. This suggests that such combined stress fields may be useful in the generation of other quantum effects at room temperature, such as formation of electron conduction bands and localization of electrons in those electron conduction bands (Wilmer et al, 2016).…”

Automated polarization-dependent multidimensional coherent spectroscopy phased using transient absorption

“…Two-dimensional optical coherent spectroscopy techniques are typically three-pulse measurements of the complex third-order nonlinear susceptibility through the four-wave mixing (FWM) response [1]. Microscopic variations in the local electronic environment [2][3][4][5] or many-body effects [6][7][8][9] cause subtle changes in the frequency-dependent third-order nonlinear susceptibility. Dependence on multi-pulse polarization configurations provides even more information by suppressing or enhancing particular features through the use of selection rules.…”