Exciton spin noise in quantum wells

Abstract

A theory of spin fluctuations of excitons in quantum wells in the presence of non-resonant excitation has been developed. Both bright and dark excitonic states have been taken into account. The effect of a magnetic field applied in a quantum well plane has been analyzed in detail. We demonstrate that in relatively small fields the spin noise spectrum consists of a single peak centered at a zero frequency while an increase of magnetic field results in the formation of the second peak in the spectrum owing to an interplay of the Larmor effect of the magnetic field and the exchange interaction between electrons and holes forming excitons. Experimental possibilities to observe the exciton spin noise are discussed, particularly, by means of ultrafast spin noise spectroscopy. We show that the fluctuation spectra contain, in addition to individual contributions of electrons and holes, an information about correlation of their spins.

Spin noise of electrons and holes in (In,Ga)As quantum dots: Experiment and theory

“…Hence, we are interested in the frequency spectra of the electron and hole spin fluctuations defined as [16,28]:…”

Universal power law decay of spin polarization in double quantum dot

“…(17). We note, that the spin noise spectrum can be also calculated directly in the frequency domain replacing the time derivatives in equations of motion with the multipliers −iω [35].…”

Spin fluctuations of nonequilibrium electrons and excitons in semiconductors

“…It follows from Ref. [74] that if the exchange splitting between the optically active and inactive doublets δ 0 is sufficiently large as compared with the decay rates of excitons and spins expressed in energy units, then in the exciton spin noise spectra at small and moderate magnetic fields, B |δ 0 /(gµ B )| (recall that g is the electron g-factor, hole Zeeman effect in the transverse field is negligibly small [75]), there is one peak centered at the zero frequency and corresponding to correlated fluctuations of the electron and hole spins. An increase in the magnetic field results in the broadening and suppression of the peak.…”

“…The role of such a competition in excitonic spin fluctuations has been theoretically investigated in Ref. [74].…”