Correlated induced electron and spin “gratings” in nanostructured $\mathrm{CdSe/CdS}$

V. V. Samartsev ; T. G. Mitrofanova

Učënye zapiski Kazanskogo universiteta. Seriâ Fiziko-matematičeskie nauki, Uchenye Zapiski Kazanskogo Universiteta. Seriya Fiziko-Matematicheskie Nauki, Tome 160 (2018) no. 1, pp. 116-125

Résumé

The possibility and the conditions of the formation of correlated “gratings” of electrons and their spins in a semiconductor film containing $\mathrm{CdSe/CdS}$ nanoparticles (which are the quantum dots) have been studied. Notably, the induction of electron spin “gratings” on quantum dots has been considered for the first time. We have suggested to perform an excitation of the film in the two photon absorption mode using two crossed (at an angle of $60^\circ$) femtosecond laser beams. As a result of the excitation, two nonequilibrium “gratings” are induced simultaneously in the excitation area of the film. If the exciting pulses have the same polarizations, then induced “gratings” of electrons are formed. However, in the case when the exciting pulses have mutually orthogonal polarizations, the formation of induced “gratings” of electron spins takes place. The same exciting pulses excite the electrons of $\mathrm{CdSe/CdS}$ nanoparticles into a superposition state. Then the free induction decay signal is generated. This signal being diffracted by induced “gratings” plays the role of a probe pulse in the suggested experimental scheme. The diffracted signals propagating in two mutually opposite directions are correlated (i.e., they are identical). Their wavefronts can carry the correlated transient holograms. Other possible applications of correlated “gratings” (in spintronics and in coherent femtosecond laser spectroscopy) are also discussed.

Détail

Keywords: correlated signals, quantum dots, induced electron and spin “gratings”, polarization, coincidence scheme, nonreversible relaxation time, coherent spectroscopy, spintronics.