Negative initial phase shift of Kerr rotation generated from the building-up process of resident electron spin polarization in a CdTe single quantum well

Abstract

Initial phase shift in a precessional motion of resident electron-spin polarization is studied in a CdTe/Cd 0.85 Mg 0.15 Te single quantum well using a time-resolved Kerr rotation technique. The generation dynamics of resident electron-spin polarization involve the formation and transformation of the associated optically excited states and are complicated particularly in the early time region. A careful analysis of the phase shift gives a deep understanding of the generation processes. In the experiments, the negative phase shift of the resident electron-spin polarization is observed, and the mechanism associated especially with a quick hole spin flip in negative trions is studied through the dependences on excitation power and magnetic field strength.

Excitation energy dependence of initial phase shift in Kerr rotation of resident electron spin polarization in a CdTe single quantum well

“…Therefore, the initial phase of the RESP precession plays out a slightly negative IPS according to this experimental result. The negative IPS is very interesting because it requires the asymmetric hole spin‐flips, which was confirmed by some measurements such as the power dependence of an additional pump pulse and so on .…”

“…The resident electrons can interact with optically injected e–hh pairs to form negative trion states. The n ‐type doping and the formation of negative trions were confirmed by TRKR measurements .…”

“…). Depending on the hole spin‐flip time, the trion lifetime, and the precession period (Larmor frequency), the amplitude and phase of the TRKR signals originated from RESP may change intricately . Since the lifetime of the trions is less than 100 ps, the oscillatory dumping component with a long coherence in the TRKR signal can confidently be associated with RESP.…”

“…Also, since the pulse width (2 ps) is much shorter than the precession period of RESP, the spin rotation during the pulse can be neglected. The generation process in the case of trion resonant excitation and the first observation of the negative IPS are detailed in the previous study .…”

“…We have observed and analyzed the initial phase shift (IPS) phenomenon of the time‐resolved Kerr rotation (TRKR) signals of the RESP component at time origin (), as shown later (Fig. ) . Since the IPS gives the important clues concerning the generation processes of RESP, we consider that the experimental and theoretical studies of IPS play a crucial role in the study of RESP.…”