37,269 research outputs found
Spin-drag relaxation time in one-dimensional spin-polarized Fermi gases
Spin propagation in systems of one-dimensional interacting fermions at finite
temperature is intrinsically diffusive. The spreading rate of a spin packet is
controlled by a transport coefficient termed "spin drag" relaxation time
. In this paper we present both numerical and analytical
calculations of for a two-component spin-polarized cold Fermi
gas trapped inside a tight atomic waveguide. At low temperatures we find an
activation law for , in agreement with earlier calculations of
Coulomb drag between slightly asymmetric quantum wires, but with a different
and much stronger temperature dependence of the prefactor. Our results provide
a fundamental input for microscopic time-dependent spin-density functional
theory calculations of spin transport in 1D inhomogeneous systems of
interacting fermions.Comment: 7 pages, 5 figure
Valley-Polarized Quantum Anomalous Hall Phase in Bilayer Graphene with Layer-Dependent Proximity Effects
Realizations of some topological phases in two-dimensional systems rely on
the challenge of jointly incorporating spin-orbit and magnetic exchange
interactions. Here, we predict the formation and control of a fully
valley-polarized quantum anomalous Hall effect in bilayer graphene, by
separately imprinting spin-orbit and magnetic proximity effects in different
layers. This results in varying spin splittings for the conduction and valence
bands, which gives rise to a topological gap at a single Dirac cone. The
topological phase can be controlled by a gate voltage and switched between
valleys by reversing the sign of the exchange interaction. By performing
quantum transport calculations in disordered systems, the chirality and
resilience of the valley-polarized edge state are demonstrated. Our findings
provide a promising route to engineer a topological phase that could enable
low-power electronic devices and valleytronic applications.Comment: Final published version. PRB letter:
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.104.L16111
Influence of Nuclear Spin Polarization on Quantum Wire Conductance
In this work, we study a possibility to measure the transverse and
longitudinal relaxation times of a collection of polarized nuclear spins
located in the region of a quantum wire via its conductance. The interplay of
an external in-plane magnetic field, spin-orbit interaction, and the changing
field of the spin-polarized nuclei cause the conductance of the quantum wire to
evolve in time. We show that it is possible to extract the transverse and
longitudinal relaxation times of the spin-polarized nuclei from the time
dependence of the conductance.Comment: Presented at the 2004 IEEE NTC Quantum Device Technology Worksho
Spintronics: Fundamentals and applications
Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes
from the published versio
Spintronic Spin Accumulation and Thermodynamics
The spin degree of freedom can play an essential role in determining the
electrical transport properties of spin-polarized electron systems in metals or
semiconductors. In this article, I address the dependence of spin-subsystem
chemical potentials on accumulated spin-densities. I discuss both approaches
which can be used to measure this fundamental thermodynamic quantity and the
microscopic physics which determines its value in several different systems.Comment: 14 pages, 4 figures. Based on lecture given at the XVI Sitges
Conference, June 1999. Proceedings to be published by Springer-Verla
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