259 research outputs found
Theory of Neutron Diffraction from the Vortex Lattice in UPt3
Neutron scattering experiments have recently been performed in the
superconducting state of UPt3 to determine the structure of the vortex lattice.
The data show anomalous field dependence of the aspect ratio of the unit cell
in the B phase. There is apparently also a change in the effective coherence
length on the transition from the B to the C phases. Such observations are not
consistent with conventional superconductvity. A theory of these results is
constructed based on a picture of two-component superconductivity for UPt3. In
this way, these unusual observations can be understood. There is a possible
discrepancy between theory and experiment in the detailed field dependence of
the aspect ratio.Comment: 11 pages; uses REVTEX, APS and PRABIB styles; 2 Postscript figure
files include
Theory of Electron Spin Relaxation in ZnO
Doped ZnO is a promising material for spintronics applications. For such
applications, it is important to understand the spin dynamics and particularly
the spin coherence of this II-VI semiconductor. The spin lifetime
has been measured by optical orientation experiments, and it shows a surprising
non-monotonic behavior with temperature. We explain this behavior by invoking
spin exchange between localized and extended states. Interestingly, the effects
of spin-orbit coupling are by no means negligible, in spite of the relatively
small valence band splitting. This is due to the wurtzite crystal structure of
ZnO. Detailed analysis allows us to characterize the impurity binding energies
and densities, showing that optical orientation experiments can be used as a
characterization tool for semiconductor samples.Comment: 7 pages, 1 figure: minor changes Accepted by Phys. Rev.
Vortex lattice structures of SrRuO
The vortex lattice structures of SrRuO for the odd parity
representations of the superconducting state are examined for the magnetic
field along the crystallographic directions. Particular emphasis is placed upon
the two dimensional representation which is believed to be relevant to this
material. It is shown that when the zero-field state breaks time reversal
symmetry, there must exist two superconducting transitions when there is a
finite field along a high symmetry direction in the basal plane. Also it is
shown that a square vortex lattice is expected when the field is along the
-axis. The orientation of the square lattice with respect to the underlying
ionic lattice yields information as to which Ru 4d orbitals are relevant to the
superconducting state.Comment: 5 pages, 2 figure
model of superconducting UPt
The phase diagram of superconducting UPt is explained in a
Ginzburg-Landau theory starting from the hypothesis that the order parameter is
a pseudo-spin singlet which transforms according to the representation
of the point group. We show how to compute the positions of the phase
boundaries both when the applied field is in the basal plane and when it is
along the c-axis. The experimental phase diagrams as determined by longitudinal
sound velocity data can be fit using a single set of parameters. In particular
the crossing of the upper critical field curves for the two field directions
and the apparent isotropy of the phase diagram are reproduced. The former is a
result of the magnetic properties of UPt and their contribution to the free
energy in the superconducting state. The latter is a consequence of an
approximate particle-hole symmetry. Finally we extend the theory to finite
pressure and show that, in contrast to other models, the model
explains the observed pressure dependence of the phase boundaries.Comment: RevTex, 29 pages, 18 PostScript figures in a uuencoded, gzipped tar
file. PostScript version of paper, tar file of PostScript figures and
individual PostScript figures are also available via anonymous ftp at
ftp://nym.physics.wisc.edu/anonymou/papers/upt3
Single-shot measurement of triplet-singlet relaxation in a Si/SiGe double quantum dot
We investigate the lifetime of two-electron spin states in a few-electron
Si/SiGe double dot. At the transition between the (1,1) and (0,2) charge
occupations, Pauli spin blockade provides a readout mechanism for the spin
state. We use the statistics of repeated single-shot measurements to extract
the lifetimes of multiple states simultaneously. At zero magnetic field, we
find that all three triplet states have equal lifetimes, as expected, and this
time is ~10 ms. At non-zero field, the T0 lifetime is unchanged, whereas the T-
lifetime increases monotonically with field, reaching 3 seconds at 1 T.Comment: 4 pages, 3 figures, supplemental information. Typos fixed; updated to
submitted versio
Inequities in treatments and outcomes among patients hospitalized with hypertrophic cardiomyopathy in the United States
Background Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiac disease. In small studies, sociodemographic factors have been associated with disparities in septal reduction therapy, but little is known about the association of sociodemographic factors with HCM treatments and outcomes more broadly. Methods and Results Using the National Inpatient Survey from 2012 to 2018, HCM diagnoses and procedures were identified b
Association between diagnosis code expansion and changes in 30-day risk-adjusted outcomes for cardiovascular diseases
BACKGROUND In January 2011, Centers for Medicare and Medicaid Services expanded the number of inpatient diagnosis codes from 9 to 25, which may influence comorbidity counts and risk-adjusted outcome rates for studies spanning January 2011. This study examines the association between (1) limiting versus not limiting diagnosis codes after 2011, (2) using inpatient-only versus inpatient and outpatient data, and (3) using logistic regression versus the Centers for Medicare and Medicaid Services risk-standardized methodology and changes in risk-adjusted outcomes. METHODS AND RESULTS Using 100% Medicare inpatient and outpatient files between January 2009 and December 2013, we created 2 cohorts of fee-for-service beneficiaries aged ≥65 years. The acute myocardial infarction cohort and the heart failure cohort had 578 728 and 1 595 069 hospitalizations, respectively. We calculate comorbidities using (1) inpatient-only limited diagnoses, (2) inpatient-only unlimited diagnoses, (3) inpatient and outpatient limited diagnoses, and (4) inpatient and outpatient unlimited diagnoses. Across both cohorts
- …