17,272 research outputs found
Spin polarization in the Hubbard model with Rashba spin-orbit coupling on a ladder
The competition between on-site Coulomb repulsion and Rashba spin-orbit
coupling (RSOC) is studied on two-leg ladders by numerical techniques. By
studying persistent currents in closed rings by exact diagonalization, it is
found that the contribution to the current due to the RSOC V_{SO}, for a fixed
value of the Hubbard repulsion U reaches a maximum at intermediate values of
V_{SO}. By increasing the repulsive Hubbard coupling U, this spin-flipping
current is suppressed and eventually it becomes opposite to the spin-conserving
current. The main result is that the spin accumulation defined as the relative
spin polarization between the two legs of the ladder is enhanced by U. Similar
results for this Hubbard-Rashba model are observed for a completely different
setup in which two halves of the ladders are connected to a voltage bias and
the ensuing time-dependent regime is studied by the density
matrix-renormalization group technique. It is also interesting a combined
effect between V_{SO} and U leading to a strong enhancement of
antiferromagnetic order which in turn may explain the observed behavior of the
spin-flipping current. The implications of this enhancement of the spin-Hall
effect with electron correlations for spintronic devices is discussed.Comment: 7 pages, 8 figure
Properties of thermal quantum states: locality of temperature, decay of correlations, and more
We review several properties of thermal states of spin Hamiltonians with
short range interactions. In particular, we focus on those aspects in which the
application of tools coming from quantum information theory has been specially
successful in the recent years. This comprises the study of the correlations at
finite and zero temperature, the stability against distant and/or weak
perturbations, the locality of temperature and their classical simulatability.
For the case of states with a finite correlation length, we overview the
results on their energy distribution and the equivalence of the canonical and
microcanonical ensemble.Comment: v1: 10 pages, 4 figures; v2: minor changes, close to published
versio
Landscape Boolean Functions
In this paper we define a class of Boolean and generalized Boolean functions
defined on with values in (mostly, we consider
), which we call landscape functions (whose class containing generalized
bent, semibent, and plateaued) and find their complete characterization in
terms of their components. In particular, we show that the previously published
characterizations of generalized bent and plateaued Boolean functions are in
fact particular cases of this more general setting. Furthermore, we provide an
inductive construction of landscape functions, having any number of nonzero
Walsh-Hadamard coefficients. We also completely characterize generalized
plateaued functions in terms of the second derivatives and fourth moments.Comment: 19 page
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