17,174 research outputs found
Spin filtering implemented through Rashba and weak magnetic modulations
We present two theoretical schemes for spin filters in one-dimensional
semiconductor quantum wires with spatially modulated Rashba spin-orbit coupling
(SOC) as well as weak magnetic potential. For case I, the SOC is periodic and
the weak magnetic potential is applied uniformly along the wire. Full spin
polarizations with opposite signs are obtained within two separated energy
intervals. For case II, the weak magnetic potential is periodic while the SOC
is uniform. An ideal negative/positive switching effect for spin polarization
is realized by tuning the strength of SOC. The roles of SOC, magnetic
potential, and their coupling on the spin filtering are analyzed.Comment: 4 pages, 4 figure
The Sorting Index and Permutation Codes
In the combinatorial study of the coefficients of a bivariate polynomial that
generalizes both the length and the reflection length generating functions for
finite Coxeter groups, Petersen introduced a new Mahonian statistic ,
called the sorting index. Petersen proved that the pairs of statistics
and have the same joint distribution over
the symmetric group, and asked for a combinatorial proof of this fact. In
answer to the question of Petersen, we observe a connection between the sorting
index and the B-code of a permutation defined by Foata and Han, and we show
that the bijection of Foata and Han serves the purpose of mapping
to . We also give a type analogue of the
Foata-Han bijection, and we derive the quidistribution of and over signed
permutations. So we get a combinatorial interpretation of Petersen's
equidistribution of and . Moreover, we show that
the six pairs of set-valued statistics ,
, , ,
and are equidistributed over signed
permutations. For Coxeter groups of type , Petersen showed that the two
statistics and are equidistributed. We introduce two statistics
and for elements of and we prove that the two
pairs of statistics and are
equidistributed.Comment: 25 page
Energy Spectra of Anti-nucleons in Finite Nuclei
The quantum vacuum in a many-body system of finite nuclei has been
investigated within the relativistic Hartree approach which describes the bound
states of nucleons and anti-nucleons consistently. The contributions of the
Dirac sea to the source terms of the meson-field equations are taken into
account up to the one-nucleon loop and one-meson loop. The tensor couplings for
the - and -meson are included in the model. The overall nucleon
spectra of shell-model states are in agreement with the data. The calculated
anti-nucleon spectra in the vacuum differ about 20 -- 30 MeV with and without
the tensor-coupling effects.Comment: 4 pages, to appear in the Proceedings of MENU 2004 (Beijing, Aug. 29
-- Sept. 4, 2004
Ideal switching effect in periodic spin-orbit coupling structures
An ideal switching effect is discovered in a semiconductor nanowire with a
spatially-periodic Rashba structure. Bistable `ON' and `OFF' states can be
realized by tuning the gate voltage applied on the Rashba regions. The energy
range and position of `OFF' states can be manipulated effectively by varying
the strength of the spin-orbit coupling (SOC) and the unit length of the
periodic structure, respectively. The switching effect of the nanowire is found
to be tolerant of small random fluctuations of SOC strength in the periodic
structure. This ideal switching effect might be applicable in future spintronic
devices.Comment: 4 pages and 4 figure
Pâ64: UVâLightâModified Polyimide Films for LiquidâCrystal Alignment
Infrared, UVâvisible and Xâray photoelectron spectroscopy measurements indicate that bondâbreaking and oxidation occur during broadband UVâillumination of the polyimide film in the air. Surface tension and polarity are increased based on the measurements of contact angles. No obvious morphology change has been observed through atomic force microscopy analysis. While the polarized UVâlight generates a relatively small pretilt angle on a nonrubbed surface, it reduces the pretilt angle to some degree on a rubbed surface, depending upon the UVâlight polarization direction relative to the rubbing direction.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92039/1/1.1833863.pd
Preprint arXiv: arXiv:2209.08871 Submitted on 19 Sep 2022
We provide further analytical insights into the newly established noninteracting (free-fermion) Page curve, focusing on both the kinematic and dynamical aspects. First, we unveil the underlying canonical typicality and atypicality for random free-fermion states. The former appears for a small subsystem and is exponentially weaker than the well-known result in the interacting case. The latter explains why the free-fermion Page curve differs remarkably from the interacting one when the subsystem is macroscopically large, i.e., comparable with the entire system. Second, we find that the free-fermion Page curve emerges with unexpectedly high accuracy in some simple tight binding models in long-time quench dynamics. This contributes a rare analytical result concerning quantum thermalization on a macroscopic scale, where conventional paradigms such as the generalized Gibbs ensemble and quasi-particle picture are not applicable
- âŠ