Quantum Interference Controls the Electron Spin Dynamics in n -GaAs

Abstract

Manifestations of quantum interference effects in macroscopic objects are rare. Weak localization is one of the few examples of such effects showing up in the electron transport through solid state. Here, we show that weak localization becomes prominent also in optical spectroscopy via detection of the electron spin dynamics. In particular, we find that weak localization controls the free electron spin relaxation in semiconductors at low temperatures and weak magnetic fields by slowing it down by almost a factor of two in n-doped GaAs in the metallic phase. The weak localization effect on the spin relaxation is suppressed by moderate magnetic fields of approximately 1 T, which destroy the interference of electron trajectories, and by increasing the temperature. The weak localization suppression causes an anomalous decrease of the longitudinal electron spin relaxation time T 1 with magnetic field, in stark contrast with the well-known magnetic-field-induced increase in T 1 . This is consistent with transport measurements, which show the same variation of resistivity with magnetic field. Our discovery opens up a vast playground to explore quantum magnetotransport effects optically in the spin dynamics.

Quantum Interference Effect on Exciton Transport in Monolayer Semiconductors

“…This effect gives rise to the coherent backscattering of excitons [33,34], and provides the key contribution to the quantum correction to the diffusion coefficient [15,16,26,31,35,36]. The weak localization is usually studied in electronic systems at reduced temperatures by the conductivity measurements [31,36,37] arXiv:1911.10528v1 [cond-mat.mes-hall] 24 Nov 2019 with very few exceptions including non-degenerate electron gases [38,39] and quite recently optically via the spin-Kerr effect [40].…”

Microscopic dynamics of electron hopping in a semiconductor quantum well probed by spin-dependent photon echoes

“…Understanding the charge and spin dynamics in condensed matter is essential for the development of novel spintronic devices in which the combination of charge transport with ultrafast spin initialization using optical pulses can be exploited [1][2][3][4][5]. In semiconductors, conduction band electrons which are localized on donor atoms or potential fluctuations, demonstrate long spin relaxation times due to suppression of spin-orbit effects [6].…”

Coherent quantum dynamics of systems with coupling-induced creation pathways

“…A particularly promising approach involves the quantum interference of multiple excitation/creation pathways, which coherently drives a system between states in the time domain. These processes have led to a diverse set of important phenomena, including governing the dynamics of electron spins in semiconductors [18], many-body oscillations in cold atoms [19], superconducting flux qubits in Josephson junctions [20], inversionless laser oscillations in atomic media [21], and polarization entanglement between photon pairs emitted from biexcitons [22], to name a few. Here, we propose and demonstrate a new class of quantum interference phenomena that result when quantum states are created in and coherently converted between propagating electromagnetic cavity modes.…”

“…Rotationally symmetric microresonators support two degenerate modes for each resonance frequency, forward (clockwise) and backward (counterclockwise) traveling, arXiv:1809.06872v1 [quant-ph] 18 Sep 2018 which do not exchange energy in the absence of coupling [26]. Thus, when photons are generated inside an uncoupled microcavity they are restricted to remain in a single propagation mode and are the result of a single creation pathway (see Fig.…”