20,181 research outputs found
Bound States and Critical Behavior of the Yukawa Potential
We investigate the bound states of the Yukawa potential , using different algorithms: solving the Schr\"odinger
equation numerically and our Monte Carlo Hamiltonian approach. There is a
critical , above which no bound state exists. We study the
relation between and for various angular momentum quantum
number , and find in atomic units, , with , ,
, and .Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in
China
Generalized seniority for the shell model with realistic interactions
The generalized seniority scheme has long been proposed as a means of
dramatically reducing the dimensionality of nuclear shell model calculations,
when strong pairing correlations are present. However, systematic benchmark
calculations, comparing results obtained in a model space truncated according
to generalized seniority with those obtained in the full shell model space, are
required to assess the viability of this scheme. Here, a detailed comparison is
carried out, for semimagic nuclei taken in a full major shell and with
realistic interactions. The even-mass and odd-mass Ca isotopes are treated in
the generalized seniority scheme, for generalized seniority v<=3. Results for
level energies, orbital occupations, and electromagnetic observables are
compared with those obtained in the full shell model space.Comment: 13 pages, 8 figures; published in Phys. Rev.
Monte Carlo Hamiltonian of lattice gauge theory
We discuss how the concept of the Monte Carlo Hamiltonian can be applied to
lattice gauge theories.Comment: "Non-Perturbative Quantum Field Theory: Lattice and Beyond",
Guangzhou, China 200
The magnetoresistance and Hall effect in CeFeAsO: a high magnetic field study
The longitudinal electrical resistivity and the transverse Hall resistivity
of CeFeAsO are simultaneously measured up to a magnetic field of 45T using the
facilities of pulsed magnetic field at Los Alamos. Distinct behaviour is
observed in both the magnetoresistance Rxx({\mu}0H) and the Hall resistance
Rxy({\mu}0H) while crossing the structural phase transition at Ts \approx 150K.
At temperatures above Ts, little magnetoresistance is observed and the Hall
resistivity follows linear field dependence. Upon cooling down the system below
Ts, large magnetoresistance develops and the Hall resistivity deviates from the
linear field dependence. Furthermore, we found that the transition at Ts is
extremely robust against the external magnetic field. We argue that the
magnetic state in CeFeAsO is unlikely a conventional type of spin-density-wave
(SDW).Comment: 4 pages, 3 figures SCES2010, To appear in J. Phys.: Conf. Ser. for
SCES201
Superconductivity and Phase Diagram in (LiFe)OHFeSeS
A series of (LiFe)OHFeSeS (0 x 1)
samples were successfully synthesized via hydrothermal reaction method and the
phase diagram is established. Magnetic susceptibility suggests that an
antiferromagnetism arising from (LiFe)OH layers coexists with
superconductivity, and the antiferromagnetic transition temperature nearly
remains constant for various S doping levels. In addition, the lattice
parameters of the both a and c axes decrease and the superconducting transition
temperature T is gradually suppressed with the substitution of S for Se,
and eventually superconductivity vanishes at = 0.90. The decrease of T
could be attributed to the effect of chemical pressure induced by the smaller
ionic size of S relative to that of Se, being consistent with the effect of
hydrostatic pressure on (LiFe)OHFeSe. But the detailed
investigation on the relationships between and the crystallographic
facts suggests a very different dependence of on anion height from
the Fe2 layer or -Fe2- angle from those in FeAs-based superconductors.Comment: 6 pages, 6 figure
Doping evoluton of antiferromagnetic order and structural distortion in LaFeAsOF
We use neutron scattering to study the structural distortion and
antiferromagnetic (AFM) order in LaFeAsOF as the system is doped
with fluorine (F) to induce superconductivity. In the undoped state, LaFeAsO
exhibits a structural distortion, changing the symmetry from tetragonal (space
group ) to orthorhombic (space group ) at 155 K, and then
followed by an AFM order at 137 K. Doping the system with F gradually decreases
the structural distortion temperature, but suppresses the long range AFM order
before the emergence of superconductivity. Therefore, while superconductivity
in these Fe oxypnictides can survive in either the tetragonal or the
orthorhombic crystal structure, it competes directly with static AFM order.Comment: reference update
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