40,954 research outputs found
Solvation forces in Ising films with long-range boundary fields: density-matrix renormalization-group study
Using the quasi-exact density-matrix renormalization-group method we
calculate the solvation forces in two-dimensional Ising films of thickness L
subject to identical algebraically decaying boundary fields with various decay
exponents p. At the bulk critical point the solvation force acquires a
universal contribution which is long-ranged in L due to the critical
fluctuations, a phenomenon known as the critical Casimir effect. For p = 2, 3
and 50, we study the scaling behaviour of the solvation force along the
pseudo-phase coexistence and along the critical and sub-critical isotherms.Comment: 9 pages, 6 figures, accepted to Molecular Physic
Exotic paired phases in ladders with spin-dependent hopping
Fermions in two-dimensions (2D) when subject to anisotropic spin-dependent
hopping can potentially give rise to unusual paired states in {\it unpolarized}
mixtures that can behave as non-Fermi liquids. One possibility is a fully
paired state with a gap for fermion excitations in which the Cooper pairs
remain uncondensed. Such a "Cooper-pair Bose-metal" phase would be expected to
have a singular Bose-surface in momentum space. As demonstrated in the context
of 2D bosons hopping with a frustrating ring-exchange interaction, an analogous
Bose-metal phase has a set of quasi-1D descendent states when put on a ladder
geometry. Here we present a density matrix renormalization group (DMRG) study
of the attractive Hubbard model with spin-dependent hopping on a two-leg ladder
geometry. In our setup, one spin species moves preferentially along the leg
direction, while the other does so along the rung direction. We find compelling
evidence for the existence of a novel Cooper-pair Bose-metal phase in a region
of the phase diagram at intermediate coupling. We further explore the phase
diagram of this model as a function of hopping anisotropy, density, and
interaction strength, finding a conventional superfluid phase, as well as a
phase of paired Cooper pairs with d-wave symmetry, similar to the one found in
models of hard-core bosons with ring-exchange. We argue that simulating this
model with cold Fermi gases on spin dependent optical lattices is a promising
direction for realizing exotic quantum states.Comment: 10 pages, 12 figure
Isospin fractionation and isoscaling in dynamical nuclear collisions
Isoscaling is found to hold for fragment yields in the antisymmetrized
molecular dynamics (AMD) simulations for collisions of calcium isotopes at 35
MeV/nucleon. This suggests the applicability of statistical considerations to
the dynamical fragment emission. The observed linear relationship between the
isoscaling parameters and the isospin asymmetry of fragments supports the above
suggestion. The slope of this linear function yields information about the
symmetry energy in low density region where multifragmentation occurs.Comment: 11 pages, 6 figure
Evidence for realignment of the charge density wave state in ErTe and TmTe under uniaxial stress via elastocaloric and elastoresistivity measurements
We report the evolution of a charge density wave (CDW) state in the quasi-2D
rare-earth tritellurides (Te for =Er,Tm) as a function of in-plane
uniaxial stress. Measurements of the elastocaloric effect, resistivity, and
elastoresistivity allow us to demonstrate the importance of in-plane
antisymmetric strain on the CDW and to establish a phase diagram. We show that
modest tensile stress parallel to the in-plane -axis can reversibly switch
the direction of the ordering wavevector between the two in-plane directions.
This work establishes Te as a promising model system for the study of
strain-CDW interactions in a quasi-2D square lattice.Comment: 18 pages, 12 figure
THEORY OF DEFECTS IN CONDUCTING POLYMERS .2. APPLICATION TO POLYACETYLENE
We exploit the approach of a previous paper, based on self-consistent quantum-chemical molecular dynamics, to investigate the energetics and dynamics of excitations in conducting polymers. The predictions include the formation energies of solitons and polarons, the phenomenon of doping by alkali atoms, luminescence quenching in cis-polyacetylene, the soliton mobility in trans-polyacetylene and the non-existence of breathers in cis-polyacetylene
Bond algebraic liquid phase in strongly correlated multiflavor cold atom systems
When cold atoms are trapped in a square or cubic optical lattice, it should
be possible to pump the atoms into excited level orbitals within each well.
Following earlier work, we explore the metastable equilibrium that can be
established before the atoms decay into the wave orbital ground state. We
will discuss the situation with integer number of bosons on every site, and
consider the strong correlation "insulating" regime. By employing a spin-wave
analysis together with a new duality transformation, we establish the existence
and stability of a novel gapless "critical phase", which we refer to as a "bond
algebraic liquid". The gapless nature of this phase is stabilized due to the
emergence of symmetries which lead to a quasi-one dimensional behavior. Within
the algebraic liquid phase, both bond operators and particle flavor occupation
number operators have correlations which decay algebraically in space and time.
Upon varying parameters, the algebraic bond liquid can be unstable to either a
Mott insulator phase which spontaneously breaks lattice symmetries, or a
phase. The possibility of detecting the algebraic liquid phase
in cold atom experiments is addressed. Although the momentum distribution
function is insufficient to distinguish the algebraic bond liquid from other
phases, the density correlation function can in principle be used to detect
this new phase of matter.Comment: 15 pages, 10 figure
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