Exciton‐phonon interaction in CdS

Abstract

The absorption coefficient of CdS is measured over the whole region of the fundamental absorption edge, between liquid helium and room temperature. The experimental results are analysed and discussed in the framework of known theoretical work on exciton-phonon interaction, I n this connection the excitonic self-energy in dependence on energy and temperature is derived from the experimental data on the one hand and from theory on the other. It is shown that the absorption behaviour is determined by different mechanisms of interaction, namely i) scattering of excitons optically generated a t k = 0 and ii) manyphonon proceeses and phonon-assisted transitions. Each mechanism is subjected to a special temperature dependence, reflecting the share of the interaction with acoustic and longitudinal optical phonons, respectively.Der Absorptionskoeffizient des CdS wird iiber den gesamten Bereich der Grundgitterabsorptionskante fur Temperaturen zwischen der des flussigen Heliums und Raumtemperatur gemes,sen. Die experimentellen Ergebnisse werden im Rahmen bekannter Theorien zur Exziton-Phonon-Wechselwirkung analysiert und diskutiert. I n diesem Zusamnienhang wird die Exzitonenselbstenergie als Funktion von Energie und Temperatur einmal experimentell, zum anderen t,lieoretisch bestimmt. Es wird gezeigt, dal3 das Absorptionsverhalten von zwei verschiedenen Wechselwirkungsmechanismen gepriigt ist, niimlich 1) der Streuung bei k N 0 optisch erzeugter Exzitonen und 2) Vielphononenprozessen bzw. phononenassistierten obergangen. Jeder dieser Mechanismen unterliegt einer besonderen Temperaturabhangigkeit, welche die anteilmiil3ige Bedeutung der Wechselwirkung mit akustkchen und longitudinalen optischen Phononen widerspiegelt.

Slow Hot-Exciton Cooling and Enhanced Interparticle Excitonic Coupling in HgTe Quantum Dots

“…Furthermore, to study the exciton–phonon coupling, Raman spectroscopy is conducted (Figure c) and records two modes: 123 cm –1 (∼15.3 meV) and 141 cm –1 (∼17.5 meV), corresponding to transverse-optical (TO, E TO ) and LO phonon energy ( E LO ), respectively. The value of E LO agrees reasonably with those reported for other inorganic semiconductors, 21 meV in CdTe, 35 meV in GaAs, 31 meV in ZnSe, and 38 meV in CdS, and is consistent with former reports in bulk HgTe, , confirming the weak size dependency of LO phonon energy. Therefore, the E LO value is expected as unchanged in our size-dependent experiment.…”

Increasing Absorption Bistability of CdS at Room Temperature

“…1 : are very accurately known for CdS from earlier atudies [15] and, in fact, a good agreement with the experimental spectrum in Fig. 1 is attained.…”

Femtosecond four-wave mixing spectroscopy on CdS crystal at room temperature

“…at the high-energy side of the resonance. With increasing temperature these bands smear out with the background, and the anti-Stokes transitions become possible [13]. In Fig 3. the stimulated photon echo decay curves are depicted, those appear to have a fast decay component (the time constant of approximately 4.5 ps), which is only present if the energy of exciting pulses exceeds the threshold value of 0.4 μJ that roughly corresponds to 1 TW/cm 2 intensity.…”