Nondestructive Measurement of Nuclear Magnetization by Off-Resonant Faraday Rotation

Abstract

We report on the nondestructive measurement of nuclear magnetization in n-GaAs via cavity enhanced Faraday rotation. In contrast with the existing optical methods, this detection scheme does not require the presence of detrimental out-of-equilibrium electrons. Specific mechanisms of the Faraday rotation are identified for (i) nuclear spins situated within the localized electron orbits, these spins are characterized by fast dynamics, (ii) all other nuclear spins in the sample characterized by much slower dynamics. Our results suggest that even in degenerate semiconductors nuclear spin relaxation is limited by the presence of localized electron states and spin diffusion, rather than by Korringa mechanism.

Theory of optical spin control in quantum dot microcavities

“…In the absence of the control pulse, this situation would simply correspond to the spin precession described by Eqs. (16) with initial conditions S Indeed, similarly to the previously studied situation of the QD without the cavity [7,43,50,51] the circularly polarized pulse induces spin rotation in the (xy) plane. The spin rotation angle induced by the control pulse is defined from the phase of the spin beats in Eqs.…”

“…The spin precession between the pulses, 0 < t < T R , is described by the linear transformation exp (−t/τ s )R(Ωt), where the matrix of the operatorR can be presented according to Eqs. (17), (16)…”

“…Thus, they leave both the direction and magnitude of the spin vector S(t) unchanged, as confirmed by a numerical calculation carried out within the density matrix formalism for the condition Ω κ. Qualitatively, this can be understood by transforming to the coordinate system rotating with the Larmor frequency around the field B: In this system the ground-state electron spin is fixed whereas the direction of the electron spin incoming from the decaying excited states is changing with the frequency Ω. As a result, the spin dynamics is not modified during the third stage and closely follows Eqs (16) if Ω κ (the situation where κ is comparable to Ω is described below and in Appendix A).…”

Subsecond nuclear spin dynamics in n -GaAs

“…[4]) has considerably progressed during recent years [5][6][7][8][9]. The application of modern optical techniques like Faraday rotation [10,11], spin noise [12,13] and time-resolved photoluminescence [6,7], combined with more traditional techniques of magneto-optical spectroscopy and nuclear magnetic resonance (NMR) [14,15], gave the opportunity to identify the basic mechanisms of spin and energy relaxation in the intertwined spin systems of nuclei and resident charge carriers [16].…”

Nuclear spin cooling by helicity-alternated optical pumping at weak magnetic fields in n -GaAs

“…The spin temperature can be many orders of magnitude lower, by absolute value, than the lattice temperature [7], and it can be both positive or negative [8,9]. Its evolution in the absence of pumping is governed by various processes of spin-lattice relaxation, for example, via a quadrupole mechanism [10][11][12] and, in the case of spatial inhomogeneity, affected also by spin diffusion [13,14].…”