1,090 research outputs found
Theory of the Little-Parks effect in spin-triplet superconductors
The celebrated Little-Parks effect in mesoscopic superconducting rings has
recently gained great attention due to its potential to probe half-quantum
vortices in spin-triplet superconductors. However, despite the large number of
works reporting anomalous Little-Parks measurements attributed to
unconventional superconductivity, the general signatures of spin-triplet
pairing in the Little-Parks effect have not yet been systematically
investigated. Here we use Ginzburg-Landau theory to study the Little-Parks
effect in a spin-triplet superconducting ring that supports half-quantum
vortices; we calculate the field-induced Little-Parks oscillations of both the
critical temperature itself and the residual resistance resulting from thermal
vortex tunneling below the critical temperature. We observe two separate
critical temperatures with a single-spin superconducting state in between and
find that, due to the existence of half-quantum vortices, each minimum in the
upper critical temperature splits into two minima for the lower critical
temperature. From a rigorous calculation of the residual resistance, we confirm
that these two minima in the lower critical temperature translate into two
maxima in the residual resistance below and establish the general conditions
under which the two maxima can be practically resolved. In particular, we
identify a fundamental trade-off between sharpening each maximum and keeping
the overall magnitude of the resistance large. Our results will guide
experimental efforts in designing mesoscopic ring geometries for probing
half-quantum vortices in spin-triplet candidate materials on the device scale
Parity Mixed Doublets in A = 36 Nuclei
The -circular polarizations () and asymmetries
() of the parity forbidden M1 + E2 -decays: MeV) and MeV)
MeV) are investigated theoretically. We use the recently proposed
Warburton-Becker-Brown shell-model interaction. For the weak forces we discuss
comparatively different weak interaction models based on different assumptions
for evaluating the weak meson-hadron coupling constants. The results determine
a range of values from which we find the most probable values:
= for and = for .Comment: RevTeX, 17 pages; to appear in Phys. Rev.
Nonlinear PDEs for Fredholm determinants arising from string equations
String equations related to 2D gravity seem to provide, quite naturally and
systematically, integrable kernels, in the sense of Its-Izergin-Korepin and
Slavnov. Some of these kernels (besides the "classical" examples of Airy and
Pearcey) have already appeared in random matrix theory and they have a natural
Wronskian structure, given by one of the operators in the string relation
, namely . The kernels are intimately related to
wave functions for Gel'fand-Dickey reductions of the KP hierarchy. The Fredholm
determinants of these kernels also satisfy Virasoro constraints leading to PDEs
for their log derivatives, and these PDEs depend explicitly on the solutions of
Painlev\'e-like systems of ODEs equivalent to the relevant string relations. We
give some examples coming from critical phenomena in random matrix theory
(higher order Tracy-Widom distributions) and statistical mechanics (Ising
models).Comment: Accepted for publication on the AMS Contemporary Mathematics Series,
36 page
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