Berlin 2015 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 95: Spintronics: Mobile Electrons and Holes (jointly with HL, MA)

TT 95.4: Vortrag

Donnerstag, 19. März 2015, 10:45–11:00, ER 164

Electric control of spin transport in GaAs (111)B quantum wells — •Alberto Hernández-Mínguez, Klaus Biermann, and Paulo Santos — Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany

The main challenge towards the use of electron spins in semiconductors is the control of the dephasing mechanisms that reduce the spin lifetime below the spin manipulation time. In III-V semiconductors, the main relaxation processes are related to the spin-orbit interaction (SOI). In the case of GaAs(111) quantum wells (QWs), the SOI can be efficiently suppressed for out-of-plane spins by applying an electric field, E_z, transverse to the QW plane. In this case, the contribution to the SOI induced by E_z compensates the intrinsic SOI due to the zinc-blende lattice and spin lifetimes of tenths of ns are observed.

In this contribution, we show experimental studies of both carrier and spin diffusion in a GaAs(111) QW under the effect of vertical electric fields. Spin polarized electron-hole pairs are optically generated in the QW by a tightly focused laser beam. The carrier and spin dynamics are studied by spatially and time-resolved photoluminescence. We show that the enhancement of the spin lifetime due to SOI compensation allows the transport of out-of-plane electron spins over distances exceeding 10 µm. In addition to the spin lifetime, the spin diffusion coefficient D_s also depends on E_z. For the carrier densities and temperatures studied, D_s shows a maximum of approx. 50 cm²/s at SOI compensation, where it approaches the values observed for the carrier diffusion coefficient under the same experimental conditions.