Spin Effects in Exciton–Polariton Condensates
Exciton–polaritons in microcavities form an unusual gas of weakly interacting bosons. It has no direct analogy in cold atomic gases, superfluids or superconductors due to its two-component spin structure: in typical planar microcavities the polaritons have two allowed spin projections to the structure axis. This is why the order parameter of a polariton condensate is a complex spinor. The magnitude and, possibly, sign of polariton–polariton interaction constant depends on the spin state of polaritons. The energy of an exciton–polariton condensate is also spin-dependent. These specific features make polariton condensates a unique laboratory for studies of spin effects in interacting Bose gases. Several new spin-dependent effects in polariton condensates have been theoretically predicted and experimentally observed during the recent decade. This review chapter addresses some of these effects: polarisation multistability, spin switching, spin rings and spin Meissner effect. In the last section we address the perspective of observation of spin superfluidity in microcavities.
KeywordsSpin Current Will Emit Trigger Pulse Spin Switching Polariton Branch
This work has been supported by the EU ITN project “CLERMONT4” and the IRSES project “POLAPHEN”. The author is deeply grateful to Yura Rubo, Tim Liew, Ivan Shelykh, Kirill Kavokin, Masha Vladimirova, Alberto Bramati, Alberto Amo, Daniele Sanvitto, Nikolay Gippius, Dima Krizhanovskii, Maurice Skolnick, Mike Kaliteevski, Konstantinos and Pavlos Lagoudakis, Luis Vina, Jeremy Baumberg and Jacqueline Bloch for many years of fruitful collaboration in the area of spin-related effects in microcavities.