[15a-501-1~10] 10.4 Semiconductor spintronics, superconductor, multiferroics

▲ [15a-501-4] Origin of long-lived spin dynamics in undoped GaAs quantum wells

〇Haruki Sanada¹, Yoji Kunihashi¹, Yusuke Tanaka¹, Hideki Gotoh¹, Koji Onomitsu¹, Makoto Kohda², Junsaku Nitta², Tetsuomi Sogawa¹ (1.NTT-BRL, 2.Tohoku Univ.)

Keywords:spin relaxation, spin orbit interaction, dark exciton

Finding a way to preserve spins in non-magnetic semiconductors is essential for future spin-based electronics. The spins of excitons have been widely explored because the polarization-dependent selection rule of inter-band optical transition provides rich information about their spins. However, the time scale on which we can measure the exciton spins is limited by the radiative lifetime, which is often less than 1 ns. In this report, we discuss the origin of the unexpectedly long decay time (>10 ns) of a Kerr rotation (KR) signal observed in an undoped GaAs quantum well (QW). We consider a probable cause of the observed long KR decay is the existence of spin-polarized dark excitons. Additional data also gave us the opportunity to discuss spin diffusion and spin-orbit interaction for the dark excitons, which have not previously been closely investigated. The ability to access the dark exciton spins might offer the possibility of memorizing quantum information in solid state systems.