Long-lived, room-temperature electron spin coherence in colloidal CdS quantum dots

Abstract

Time-resolved Faraday rotation spectroscopy is used to study the electron spin coherence in colloidal CdS quantum dots. Long-lived spin coherence with dephasing time T2*>3ns has been found at room temperature. Spin dynamics unaffected by the faster carrier recombination suggests the spin signal coming from the residual electrons in the dots. A small external transverse magnetic field of 50 mT can extend T2* ∼ 2 times longer compared with that in zero magnetic field. Hyperfine interaction between electron and nuclear spins limits the dephasing time in zero or low magnetic field, while for higher magnetic fields, inhomogeneous dephasing becomes to dominate the spin dynamics.

Enhanced electron spin rotation in CdS quantum dots

“…The estimate is smaller than the measured increase of 0.2, but the g-factor of 1.965±0.006 is regarded as the gfactor of electron in CdS QDs 3.0 nm in diameter. Similar electron g-factor of 1.93 was reported for CdS QDs 5.6 nm in diameter 2 .…”

“…It is desirable for electron spins to be coherent for long time at room temperature. Time-resolved Faraday rotation (TRFR) was used to measure the excitonic population and spin rotation of electrons in CdSe and CdS QDs under the transverse magnetic field at room temperature 1,2 . Low natural abundance of nuclear spins and small hyperfine constant of Cd make spin coherence time of electrons in CdSe and CdS QDs long.…”

Room-temperature spin coherence in zinc blende CdSe quantum dots studied by time-resolved Faraday ellipticity

“…Therefore, the electron g e factor implicitly depends on the size of QDs. The g e ¼ 1.64 (d ¼5.8 nm) for current work at room temperature is much larger than g l ¼1.138 (d ¼5.7 nm) for CdSe QDs at T¼ 5 K [11], while it is a little bit smaller than g e ¼1.93 (d ¼5.6 nm) for CdS QDs at room temperature [27]. It is notable that a single g-factor is observed in the zinc blende CdSe QDs, while multiple g-factors were reported in the wurtzite CdSe QDs [11].…”

Coherent Spin Precession and Lifetime-Limited Spin Dephasing in CsPbBr3 Perovskite Nanocrystals

“…* upon application of the transverse magnetic field below 50 K to field-induced suppression of local magnetic-field inhomogeneities due to nuclear hyperfine interactions that accelerate dephasing. 20,33,[48][49][50] The highly ionic nature of the metal-halide perovskite lattice and the large Pb(6s) contribution to the carrier wavefunction at the valence-band edge favor strong Fermi-contact hyperfine coupling (Table S2). [50][51][52] Accumulation of Pb 2+ nuclear spin polarization may further exacerbate the effect of inhomogeneous nuclear magnetic fields.…”