115 research outputs found
Ballistic Quantum Transport: Effect of Geometrical Phases
We study the influence of nonuniform magnetic fields on the magneto
conductance of mesoscopic microstructures. We show that the coupling of the
electron spin to the inhomogenous field gives rise to effects of the Berry
phase on ballistic quantum transport and discuss adiabaticity conditions
required to observe such effects. We present numerical results for different
ring geometries showing a splitting of Aharonov-Bohm conductance peaks for
single rings and corresponding signatures of the geometrical phase in weak
localization. The latter features can be qualitatively explained in a
semiclassical approach to quantum transport.Comment: 15 pages, 6 figures. Accepted for publication in Foundations of
Physic
Entanglement production in chaotic quantum dots subject to spin-orbit coupling
We study numerically the production of orbital and spin entangled states in
chaotic quantum dots for non-interacting electrons. The introduction of
spin-orbit coupling permit us to identify signatures of time-reversal symmetry
correlations in the entanglement production previously unnoticed, resembling
weak-(anti)localization quantum corrections to the conductance. We find the
entanglement to be strongly dependent on spin-orbit coupling, showing universal
features for broken time-reversal and spin-rotation symmetries.Comment: 6 pages; extended versio
Signatures of spin-related phases in transport through regular polygons
We address the subject of transport in one-dimensional ballistic polygon
loops subject to Rashba spin-orbit coupling. We identify the role played by the
polygon vertices in the accumulation of spin-related phases by studying
interference effects as a function of the spin-orbit coupling strength. We find
that the vertices act as strong spin-scattering centers that hinder the
developing of Aharovov-Casher and Berry phases. In particular, we show that the
oscillation frequency of interference pattern can be doubled by modifying the
shape of the loop from a square to a circle.Comment: 4 pages, 4 figures. To appear in Phys. Rev.
The role of orbital dynamics in spin relaxation and weak antilocalization in quantum dots
We develop a semiclassical theory for spin-dependent quantum transport to
describe weak (anti)localization in quantum dots with spin-orbit coupling. This
allows us to distinguish different types of spin relaxation in systems with
chaotic, regular, and diffusive orbital classical dynamics. We find, in
particular, that for typical Rashba spin-orbit coupling strengths, integrable
ballistic systems can exhibit weak localization, while corresponding chaotic
systems show weak antilocalization. We further calculate the magnetoconductance
and analyze how the weak antilocalization is suppressed with decreasing quantum
dot size and increasing additional in-plane magnetic field.Comment: 5 page
Multi-channel architecture for electronic quantum-Hall interferometry
We propose a new architecture for implementing electronic interferometry in
quantum Hall bars. It exploits scattering among parallel edge channels. In
contrast to previous developments, this one employs a simply-connected mesa
admitting serial concatenation of building elements closer to optical
analogues. Implementations of Mach-Zehnder and Hambury-Brown-Twiss
interferometers are discussed together with new structures yet unexplored in
quantum electronics.Comment: 4 pages, 5 figure
Chiral Majorana Interference as a Source of Quantum Entanglement
Interferometry is a powerful tool for entanglement production and detection
in multiterminal mesoscopic systems. Here we propose a setup to produce,
manipulate and detect entanglement in the electron-hole degree of freedom by
exploiting Andreev reflection on chiral one-dimensional channels via
interferometry. We study the best possible case in which two-particle
interferometry produces superpositions of maximally entangled states. This is
achieved by mixing chiral Dirac channels through chiral Majorana modes. We show
that it is possible to extract entanglement witnesses through current
cross-correlation measurements.Comment: 5 pages, 1 figur
Conditions for Adiabatic Spin Transport in Disordered Systems
We address the controversy concerning the necessary conditions for the
observation of Berry phases in disordered mesoscopic conductors. For this
purpose we calculate the spin-dependent conductance of disordered
two-dimensional structures in the presence of inhomogeneous magnetic fields.
Our numerical results show that for both, the overall conductance and quantum
corrections, the relevant parameter defining adiabatic spin transport scales
with the square root of the number of scattering events, in generalization of
Stern's original proposal [Phys. Rev. Lett. 68, 1022 (1992)]. This could hinder
a clear-cut experimental observation of Berry phase effects in diffusive
metallic rings.Comment: 5 pages, 4 figures. To appear in Phys. Rev. B (Rapid Communications
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