7,402 research outputs found

### Neutrinoless double-beta decay matrix elements in large shell-model spaces with the generator-coordinate method

We use the generator-coordinate method with realistic shell-model
interactions to closely approximate full shell-model calculations of the matrix
elements for the neutrinoless double-beta decay of $^{48}$Ca, $^{76}$Ge, and
$^{82}$Se. We work in one major shell for the first isotope, in the
$f_{5/2}pg_{9/2}$ space for the second and third, and finally in two major
shells for all three. Our coordinates include not only the usual axial
deformation parameter $\beta$, but also the triaxiality angle $\gamma$ and
neutron-proton pairing amplitudes. In the smaller model spaces our matrix
elements agree well with those of full shell-model diagonalization, suggesting
that our Hamiltonian-based GCM captures most of the important valence-space
correlations. In two major shells, where exact diagonalization is not currently
possible, our matrix elements are only slightly different from those in a
single shell.Comment: 8 pages, 7 figure

### Searching for high-$K$ isomers in the proton-rich $A\sim80$ mass region

Configuration-constrained potential-energy-surface calculations have been
performed to investigate the $K$ isomerism in the proton-rich $A\sim80$ mass
region. An abundance of high-$K$ states are predicted. These high-$K$ states
arise from two and four-quasi-particle excitations, with $K^{\pi}=8^{+}$ and
$K^{\pi}=16^{+}$, respectively. Their excitation energies are comparatively
low, making them good candidates for long-lived isomers. Since most nuclei
under studies are prolate spheroids in their ground states, the oblate shapes
of the predicted high-$K$ states may indicate a combination of $K$ isomerism
and shape isomerism

### Normal heat conduction in one dimensional momentum conserving lattices with asymmetric interactions

The heat conduction behavior of one dimensional momentum conserving lattice
systems with asymmetric interparticle interactions is numerically investigated.
It is found that with certain degree of interaction asymmetry, the heat
conductivity measured in nonequilibrium stationary states converges in the
thermodynamical limit, in clear contrast to the well accepted viewpoint that
Fourier's law is generally violated in low dimensional momentum conserving
systems. It suggests in nonequilibrium stationary states the mass gradient
resulted from the asymmetric interactions may provide an additional phonon
scattering mechanism other than that due to the nonlinear interactions.Comment: 4 pages, 4 figure

### The upper critical field and its anisotropy in LiFeAs

The upper critical field $\mu_0H_{c2}(T_c)$ of LiFeAs single crystals has
been determined by measuring the electrical resistivity using the facilities of
pulsed magnetic field at Los Alamos. We found that $\mu_0H_{c2}(T_c)$ of LiFeAs
shows a moderate anisotropy among the layered iron-based superconductors; its
anisotropic parameter $\gamma$ monotonically decreases with decreasing
temperature and approaches $\gamma\simeq 1.5$ as $T\rightarrow 0$. The upper
critical field reaches 15T ($H\parallel c$) and 24.2T ($H\parallel ab$) at
$T=$1.4K, which value is much smaller than other iron-based high $T_c$
superconductors. The temperature dependence of $\mu_0H_{c2}(T_c)$ can be
described by the Werthamer-Helfand-Hohenberg (WHH) method, showing orbitally
and (likely) spin-paramagnetically limited upper critical field for $H\parallel
c$ and $H\parallel ab$, respectively.Comment: 5 pages,5 figure

### Reduced dynamics with renormalization in solid-state charge qubit measurement

Quantum measurement will inevitably cause backaction on the measured system,
resulting in the well known dephasing and relaxation. In this report, in the
context of solid--state qubit measurement by a mesoscopic detector, we show
that an alternative backaction known as renormalization is important under some
circumstances. This effect is largely overlooked in the theory of quantum
measurement.Comment: 12 pages, 4 figure

- â€¦