3,031 research outputs found
Unambiguous probe of parity-mixing of Cooper pairs in noncentrosymmetric superconductors
We propose an experimental scheme to detect unambiguously parity-mxing of
Cooper pairs in noncentrosymmetric superconductors, which utilizes crossed
Andreev reflection processes between two oppositely spin-polarized normal metal
leads and a noncentrosymmetric superconductor. It is demonstrated that a
non-local conductance exhibits a clear signature of parity breaking of Cooper
pairs, and thus, can be a direct probe for the parity-mixing.Comment: 4 pages, 2figure
Signature of superconducting states in cubic crystal without inversion symmetry
The effects of absence of inversion symmetry on superconducting states are
investigated theoretically. In particular we focus on the noncentrosymmetric
compounds which have the cubic symmetry like LiPtB. An appropriate
and isotropic spin-orbital interaction is added in the Hamiltonian and it acts
like a magnetic monopole in the momentum space. The consequent pairing
wavefunction has an additional triplet component in the pseudospin space, and a
Zeeman magnetic field can induce a collinear supercurrent
with a coefficient . The effects of anisotropy embedded in the cubic
symmetry and the nodal superconducting gap function on are also
considered. From the macroscopic perspectives, the pair of mutually induced
and magnetization can affect the distribution of magnetic
field in such noncentrosymmetric superconductors, which is studied through
solving the Maxwell equation in the Meissner geometry as well as the case of a
single vortex line. In both cases, magnetic fields perpendicular to the
external ones emerge as a signature of the broken symmetry.Comment: 16 pages in pre-print forma
âAm I Sick or Just Discarded?â : Psychiatry, Health Care Reform, and the Rise of Geriatrics in America, 1931-1954
Between 1931 and 1941, the United States population over the age of sixty-five increased by over 35 percent. These individuals, however, did not receive increased support. Rather, American politicians and society at large labeled the elderly a âburden,â and passed off their care to the overworked medical personnel of state and federal mental institutions. Sparked by clinical exposure to the influx of elderly patients to mental institutions, Massachusetts psychiatrist David Rothschild identified an erroneous assumption in care practices for senile patients. In many cases, physicians preemptively diagnosed those admitted to state and federal institutions with some form of senile dementia, without considering their personal history. Personal histories unveiled socioeconomic status, racial and gender discrimination, as well as traumatic experiences faced by many of these patients. Psychiatryâs unruly search for the biological underpinnings of mental illness overshadowed a psychiatric framework that considered both biological and social factors. Rothschild was determined to change such a mindset. Through tedious research, confrontation, and public addresses, Rothschild fostered a psychodynamic model for discerning senile psychoses. Promulgating this model, Winfred Overholserâsuperintendent of St. Elizabeths, the first federal institution for the mentally illâpushed for increased appropriations, endorsed a national health care program and developed some of the first geriatric psychiatric facilities. Using primary source newspaper articles, government hearings and proceedings, radio recordings, and census data, this thesis explores the rise, and subsequent fall, of social psychiatry through the lens of national health care reform and the path to Medicare. Such an analysis reveals the importance of refocusing psychiatric and political efforts on social structures, rather than exclusively changes in the individual
Tunnelling between non-centrosymmetric superconductors with significant spin-orbit splitting studied theoretically within a two-band treatment
Tunnelling between non-centrosymmetric superconductors with significant
spin-orbit splitting is studied theoretically in a two-band treatment of the
problem. We find that the critical Josephson current may be modulated by
changing the relative angle between the vectors describing absence of inversion
symmetry on each side of the junction. The presence of two gaps also results in
multiple steps in the quasiparticle current-voltage characteristics. We argue
that both these effects may help to determine the pairing states in materials
like CePtSi, UIr and CdReO. We propose experimental tests of
these ideas, including scanning tunnelling microscopy.Comment: 5 pages, 1 figure. Minor changes. Some new references added.
Journal-ref. adde
Enhanced triplet superconductivity in noncentrosymmetric systems
We study pairing symmetry of noncentrosymmetric superconductors based on the
extended Hubbard model on square lattice near half-filling, using the random
phase approximation. We show that d+f-wave pairing is favored and the triplet
f-wave state is enhanced by Rashba type spin-orbit coupling originating from
the broken inversion symmetry. The enhanced triplet superconductivity stems
from the increase of the effective interaction for the triplet pairing and the
reduction of the spin susceptibility caused by the Rashba type spin-orbit
coupling which lead to the increase of the triplet component and the
destruction of the singlet one, respectively.Comment: 5 pages, 5 figure
Self-dual solitons in N=2 supersymmetric semilocal Chern-Simons theory
We embed the semilocal Chern-Simons-Higgs theory into an N=2 supersymmetric
system. We construct the corresponding conserved supercharges and derive the
Bogomol'nyi equations of the model from supersymmetry considerations. We show
that these equations hold provided certain conditions on the coupling constants
as well as on the Higgs potential of the system, which are a consequence of the
huge symmetry of the theory, are satisfied. They admit string-like solutions
which break one half of the supersymmetries --BPS Chern-Simons semilocal cosmic
strings-- whose magnetic flux is concentrated at the center of the vortex. We
study such solutions and show that their stability is provided by supersymmetry
through the existence of a lower bound for the energy, even though the manifold
of the Higgs vacuum does not contain non-contractible loops.Comment: 12 pages, LaTeX, no figures, to appear in Modern Physics Letters
Supersymmetric Electroweak Cosmic Strings
We study the connection between supersymmetry and a topological bound
in a two-Higgs-doublet system with an gauge group. We derive the Bogomol'nyi equations from
supersymmetry considerations showing that they hold provided certain conditions
on the coupling constants, which are a consequence of the huge symmetry of the
theory, are satisfied. Their solutions, which can be interpreted as electroweak
cosmic strings breaking one half of the supersymmetries of the theory, are
studied. Certain interesting limiting cases of our model which have recently
been considered in the literature are finally analyzed.Comment: 20 pages, RevTe
Dramatic robustness of a multiple delay dispersed interferometer to spectrograph errors: how mixing delays reduces or cancels wavelength drift
We describe demonstrations of remarkable robustness to instrumental noises by using a multiple delay externally dispersed interferometer (EDI) on stellar observations at the Hale telescope. Previous observatory EDI demonstrations used a single delay. The EDI (also called âTEDIâ) boosted the 2,700 resolution of the native TripleSpec NIR spectrograph (950-2450 nm) by as much as 10x to 27,000, using 7 overlapping delays up to 3 cm. We observed superb rejection of fixed pattern noises due to bad pixels, since the fringing signal responds only to changes in multiple exposures synchronous to the applied delay dithering. Remarkably, we observed a ~20x reduction of reaction in the output spectrum to PSF shifts of the native spectrograph along the dispersion direction, using our standard processing. This allowed high resolution observations under conditions of severe and irregular PSF drift otherwise not possible without the interferometer. Furthermore, we recently discovered an improved method of weighting and mixing data between pairs of delays that can theoretically further reduce the net reaction to PSF drift to zero. We demonstrate a 350x reduction in reaction to a native PSF shift using a simple simulation. This technique could similarly reduce radial velocity noise for future EDIâs that use two delays overlapped in delay space (or a single delay overlapping the native peak). Finally, we show an extremely high dynamic range EDI measurement of our ThAr lamp compared to a literature ThAr spectrum, observing weak features (~0.001x height of nearest strong line) that occur between the major lines. Because of individuality of each reference lamp, accurate knowledge of its spectrum between the (unfortunately) sparse major lines is important for precision radial velocimetry
Andreev reflection from non-centrosymmetric superconductors and Majorana bound state generation in half-metallic ferromagnets
We study Andreev reflection at an interface between a half metal and a
superconductor with spin-orbit interaction. While the absence of minority
carriers in the half metal makes singlet Andreev reflection impossible, the
spin-orbit interaction gives rise to triplet Andreev reflection, i.e., the
reflection of a majority electron into a majority hole or vice versa. As an
application of our calculation, we consider a thin half metal film or wire
laterally attached to a superconducting contact. If the half metal is disorder
free, an excitation gap is opened that is proportional to the spin-orbit
interaction strength in the superconductor. For electrons with energy below
this gap a lateral half-metal--superconductor contact becomes a perfect triplet
Andreev reflector. We show that the system supports localized Majorana end
states in this limit.Comment: 14 pages, 3 figure
Phases of dual superconductivity and confinement in softly broken N=2 supersymmetric Yang-Mills theories
We study the electric flux tubes that undertake color confinement in N=2
supersymmetric Yang-Mills theories softly broken down to N=1 by perturbing with
the first two Casimir operators. The relevant Abelian Higgs model is not the
standard one due to the presence of an off-diagonal coupling among different
magnetic U(1) factors. We perform a preliminary study of this model at a
qualitative level. BPS vortices are explicitely obtained for particular values
of the soft breaking parameters. Generically however, even in the ultrastrong
scaling limit, vortices are not critical but live in a "hybrid" type II phase.
Also, ratios among string tensions are seen to follow no simple pattern. We
examine the situation at the half Higgsed vacua and find evidence for solutions
with the behaviour of superconducting strings. In some cases they are solutions
to BPS equations.Comment: 15 pages, 1 figure, revtex; v2: typos corrected, final versio
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