Spin relaxation via exchange with donor impurity-bound electrons

Qing, Lan; Li, Jing; Appelbaum, Ian; Dery, Hanan

doi:10.1103/physrevb.91.241405

Cited by 11 publications

(6 citation statements)

References 61 publications

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“…29). All these endeavours put forward the subtle role played by impurities in introducing extrinsic spin-relaxation channels5960 that in bulk Ge emerge at low temperatures and drastically prevail over the intrinsic but slower Elliott–Yafet process. By spatially separating conduction band electrons residing in the Ge QW from their parent donor atoms embedded in the SiGe barriers, we prevent the impurity-induced bottleneck pertaining to experiments utilizing bulk Ge wafers, and eventually resolve long-lived spins despite the low temperature operation.…”

Section: Resultsmentioning

confidence: 99%

Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

et al. 2016

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Control of electron spin coherence via external fields is fundamental in spintronics. Its implementation demands a host material that accommodates the desirable but contrasting requirements of spin robustness against relaxation mechanisms and sizeable coupling between spin and orbital motion of the carriers. Here, we focus on Ge, which is a prominent candidate for shuttling spin quantum bits into the mainstream Si electronics. So far, however, the intrinsic spin-dependent phenomena of free electrons in conventional Ge/Si heterojunctions have proved to be elusive because of epitaxy constraints and an unfavourable band alignment. We overcome these fundamental limitations by investigating a two-dimensional electron gas in quantum wells of pure Ge grown on Si. These epitaxial systems demonstrate exceptionally long spin lifetimes. In particular, by fine-tuning quantum confinement we demonstrate that the electron Landé g factor can be engineered in our CMOS-compatible architecture over a range previously inaccessible for Si spintronics.

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Section: Resultsmentioning

confidence: 99%

Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

et al. 2016

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“…The spin polarization of localized electrons in the presence of a magnetic field is established when they are captured or through exchange interactions with spinpolarized delocalized electrons. 115 In devices where the gate voltage is tuned to the neutral regime, delocalized electrons and holes are introduced by photo-doping (i.e., electrons and holes from dissociated excitons). Here, we assume that exchange interactions between localized and delocalized electrons are more effective in polarizing the localized electrons compared with the relatively slow spin-lattice processes that flip the spin of an isolated lo- calized electron.…”

Section: The Magnetic-field Dependence Of the Phonon-assisted Recombi...mentioning

confidence: 99%

“…Here, we assume that exchange interactions between localized and delocalized electrons are more effective in polarizing the localized electrons compared with the relatively slow spin-lattice processes that flip the spin of an isolated lo- calized electron. 115 The ratio between the majority and minority spin densities of localized electrons is then approaching the respective ratio of the delocalized electron system. Assuming a small density of delocalized electrons such that E F < k B T , and denoting the effective g-factor in the bottom of the conduction band by g cb , we can then write that…”

Section: The Magnetic-field Dependence Of the Phonon-assisted Recombi...mentioning

confidence: 99%

Localization-induced optical properties of monolayer transition-metal dichalcogenides

Van Tuan,

Dery

2019

Preprint

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Impurities play an important role during recombination processes in semiconductors. Their important role is sharpened in atomically-thin transition-metal dichalcogenides whose two-dimensional character renders electrons and holes highly susceptible to localization caused by remote charged impurities. We study a multitude of phenomena that arise from the interaction of localized electrons with excitonic complexes. Emphasis is given to the amplification of the phonon-assisted recombination of biexcitons when it is mediated by localized electrons, showing that this mechanism can explain recent photoluminescence experiments in ML-WSe2. In addition, the magnetic-field dependence of this mechanism is analyzed. The results of this work point to (i) an intriguing coupling between the longitudinal-optical and homopolar phonon modes that can further elucidate various experimental results, (ii) the physics behind a series of localization-induced optical transitions in tungsten-based materials, and (iii) the importance of localization centers in facilitating the creation of biexcitons and exciton-exciton annihilation processes.

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“…2. Before a scattering event: We randomize a value for the free flight duration with the help of the direct technique [9,79,80]…”

Section: Supplemental Information: Exciton Valley Depolarization In M...mentioning

confidence: 99%

Exciton valley depolarization in monolayer transition-metal dichalcogenides

Yang,

Robert,

et al. 2019

Preprint

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The valley degree of freedom is a sought-after quantum number in monolayer transition-metal dichalcogenides. Similar to optical spin orientation in semiconductors, the helicity of absorbed photons can be relayed to the valley (pseudospin) quantum number of photoexcited electrons and holes. Also similar to the quantum-mechanical spin, the valley quantum number is not a conserved quantity. Valley depolarization of excitons in monolayer transition-metal dichalcogenides due to long-range electron-hole exchange typically takes a few ps at low temperatures. Exceptions to this behavior are monolayers MoSe2 and MoTe2 wherein the depolarization is much faster. We elucidate the enigmatic anomaly of these materials, finding that it originates from Rashba-induced coupling of the dark and bright exciton branches next to their degeneracy point. When photoexcited excitons scatter during their energy relaxation between states next to the degeneracy region, they reach the light cone after losing the initial helicity. The valley depolarization is not as fast in monolayers WSe2, WS2 and likely MoS2 wherein the Rashba-induced coupling is negligible.

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Spin relaxation via exchange with donor impurity-bound electrons

Cited by 11 publications

References 61 publications

Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

Strong confinement-induced engineering of the g factor and lifetime of conduction electron spins in Ge quantum wells

Localization-induced optical properties of monolayer transition-metal dichalcogenides

Exciton valley depolarization in monolayer transition-metal dichalcogenides

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