Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 41: Spin Phenomena in Semiconductors

HL 41.2: Talk

Wednesday, March 19, 2025, 16:00–16:15, H17

Carrier spin coherence in inas/inalgaas quantum dots emitting in the telecom range — •Vitalie Nedelea — Technische Universität Dortmund, Dortmund, Germany

This study focuses on the carrier spin coherence in quantum dots(QDs), which are promising candidates for entanglement with an emitted photon as well as entanglement of two remote spins induced by measuring of two indistinguishable photons. The Samples, grown by molecular beam epitaxy, consist of 5.5nm InAs monolayers separated by InAlGaAs barriers. A Si δ-doped layer, at a distance of 15 nm from the QD layer, provides resident electrons. Differential transmission reveals a double exponential decay behaviour, with a short exciton(X) decay time of 0.5ns and the long indirect molecular X decay time of 2ns. The dependence of the Larmor frequencies on the transversal magnetic field (BV) gives us information about the carrier g-factor, |ge|=1.88 for the electron and |gh|=0.6 for the hole. The hole spin dephasing saturates at a higher value of T2*=1.4ns than the electron T2*=0.6ns, which could be explained by the weaker hyperfine coupling of the hole. The decay of the FR signal as a function of fm gives TS=0.3μs and extrapolating the power dependence to zero gives the spin relaxation time T1=0.5μs. The wide spread of g-factors and long spin relaxation times are promising candidates for the spin mode locking (SML) effect. In the ensemble of QDs, the sum of the multiple oscillating signals with Larmor frequencies corresponding to ωR contributes to the SML. Measured dependence of the SML on the BV reveal that the signal is related to the hole spins.

Keywords: spintronics; telecom; quantum dots