80 research outputs found
Simple mechanisms that impede the Berry phase identification from magneto-oscillations
The phase of quantum magneto-oscillations is often associated with the Berry
phase and is widely used to argue in favor of topological nontriviality of the
system (Berry phase ). Nevertheless, the experimentally determined
value may deviate from arbitrarily, therefore more care should be
made analyzing the phase of magneto-oscillations to distinguish trivial systems
from nontrivial. In this paper we suggest two simple mechanisms dramatically
affecting the experimentally observed value of the phase in three-dimensional
topological insulators: (i) magnetic field dependence of the chemical
potential, and (ii) possible nonuniformity of the system. These mechanisms are
not limited to topological insulators and can be extended to other
topologically trivial and non-trivial systems.Comment: 9 pages, 4 figures, in published version the title was change
Quantum Interference Controls the Electron Spin Dynamics in n-GaAs
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 -doped GaAs in the metallic phase. The weak localization effect on
the spin relaxation is suppressed by moderate magnetic fields of about 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 with magnetic field, in
stark contrast with well-known magnetic field induced increase in . This
is consistent with transport measurements which show the same variation of
resistivity with magnetic field. Our discovery opens a vast playground to
explore quantum magneto-transport effects optically in the spin dynamics.Comment: 8 pages, 3 figure
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