Ballistic spin transport in exciton gases

Abstract

Traditional spintronics relies on spin transport by charge carriers, such as electrons in semiconductor crystals. The challenges for the realization of long-range electron spin transport include rapid spin relaxation due to electron scattering. Scattering and, in turn, spin relaxation can be effectively suppressed in excitonic devices where the spin currents are carried by electrically neutral bosonic quasi-particles: excitons or exciton-polaritons. They can form coherent quantum liquids that carry spins over macroscopic distances. The price to pay is a finite life-time of the bosonic spin carriers. We present the theory of exciton ballistic spin transport which may be applied to a range of systems supporting bosonic spin transport, in particular, to indirect excitons in coupled quantum wells. We describe the effect of spin-orbit interaction for the electron and the hole on the exciton spin, account for the Zeeman effect induced by external magnetic fields and long range and short range exchange splittings of the exciton resonances. We also consider exciton transport in the non-linear regime and discuss the definitions of the exciton spin current, polarization current and spin conductivity.

Effects of Fermion Exchange on the Polarization of Exciton Condensates

“…in the range of the threshold distance d * for the switch of the condensate polarisation. This switch induced by fermion exchanges strikingly contrasts with recent theoretical studies [21][22][23][24] that have emphasized the role played by spin-orbit interactions in Bose-Einstein condensation of excitons.…”

Roton-maxon spectrum and instability for weakly interacting dipolar excitons in a semiconductor layer

“…In sufficiently thin QWs, systems of dipolar excitons have 2D behavior, because dynamics of dipolar exciton systems is quantized in the tight direction, and dipole moments of all excitons are equal and normal to the QW plane. Persistent currents [7], superfluidity [20,21], Josephson-like effect [22], anomalous optical properties [23], and spin effects [24][25][26][27][28] 2D dipolar excitons have been considered. Outstanding findings [29,30] have been reported on exciton BEC in e-e bilayer in strong magnetic fields.…”

Pancharatnam-Berry Phase in a Condensate of Indirect Excitons

“…This makes excitons a unique interface between matter and light, and in turn, a model system for exploring the Pancharatnam-Berry phase. Recent studies led to the discovery of polarization textures in light emission of indirect excitons (IXs) [12][13][14][15][16][17][18][19][20][21] and exciton-polaritons [22][23][24]. In this work, we report on experimental observation of the Pancharatnam-Berry phase in a condensate of IXs.…”