Hole-spin initialization and relaxation times in InAs/GaAs quantum dots

Francois Fras (1) , Benoit Eble (1) , Pascale Desfonds (1) , Frédéric Bernardot (1) , Christophe Testelin (1) , Maria Chamarro (1) , Audrey Miard (2) , Aristide Lemaître (2)

1 INSP - Institut des Nanosciences de Paris
2 LPN - Laboratoire de photonique et de nanostructures

We study, at low temperature and zero magnetic field, the hole-spin dynamics in InAs/GaAs quantum dots. We measure the hole-spin relaxation time at a time scale longer than the dephasing time (about ten nanoseconds), imposed by the hole-nuclear hyperfine coupling. We use a pump-probe configuration and compare two experimental techniques based on differential absorption. The first one works in the time domain, and the second one is a new experimental method, the dark-bright time-scanning spectroscopy (DTS), working in the frequency domain. The measured hole-spin relaxation times, using these two techniques, are very similar, in the order of TNh≈1 μs. It is mainly imposed by the inhomogeneous hole hyperfine coupling in the hole localization volume. The DTS technique allows us also to measure the hole-spin initialization time τi. The hole spin is initialized by a periodic train of circularly polarized pulses at 76 MHz; we have observed that τi decreases as the power density increases, and we have measured a minimum value of τi≈100 ns in good agreement with a simple model [see B. Eble, P. Desfonds, F. Fras, F. Bernardot, C. Testelin, M. Chamarro, A. Miard, and A. Lemaître, Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.81.045322 81, 045322 (2010)].

Mots clés: Spin relaxation and scattering; Optical creation of spin polarized carriers; Quantum dots; III-V semiconductors; hyperfine interaction; spin initialization

Domaines: Physique Quantique [quant-ph]

Francois Fras, Benoit Eble, Pascale Desfonds, Frédéric Bernardot, Christophe Testelin, et al.. Hole-spin initialization and relaxation times in InAs/GaAs quantum dots. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2011, 84, pp.125431. ⟨10.1103/PHYSREVB.84.125431⟩. ⟨hal-00913531⟩