1,644 research outputs found
Statics and dynamics of phase segregation in multicomponent fermion gas
We investigate the statics and dynamics of spatial phase segregation process
of a mixture of fermion atoms in a harmonic trap using the density functional
theory. The kinetic energy of the fermion gas is written in terms of the
density and its gradients. Several cases have been studied by neglecting the
gradient terms (the Thomas-Fermi limit) which are then compared with the
Monte-Carlo results using the full gradient corrected kinetic energy. A linear
instability analysis has been performed using the random-phase approximation.
Near the onset of instability, the fastest unstable mode for spinodal
decomposition is found to occur at . However, in the strong coupling
limit, many more modes with decay with comparable time scales.Comment: 14 figure
Reorientation transition of ultrathin ferromagnetic films
We demonstrate that the reorientation transition from out-of-plane to
in-plane magnetization with decreasing temperature as observed experimentally
in Ni-films on Cu(001) can be explained on a microscopic basis. Using a
combination of mean field theory and perturbation theory, we derive an analytic
expression for the temperature dependent anisotropy. The reduced magnetization
in the film surface at finite temperatures plays a crucial role for this
transition as with increasing temperature the influence of the uniaxial
anisotropies is reduced at the surface and is enhanced inside the film.Comment: 4 pages(RevTeX), 3 figures (EPS
Phase separation and vortex states in binary mixture of Bose-Einstein condensates in the trapping potentials with displaced centers
The system of two simultaneously trapped codensates consisting of
atoms in two different hyperfine states is investigated theoretically in the
case when the minima of the trapping potentials are displaced with respect to
each other. It is shown that the small shift of the minima of the trapping
potentials leads to the considerable displacement of the centers of mass of the
condensates, in agreement with the experiment. It is also shown that the
critical angular velocities of the vortex states of the system drastically
depend on the shift and the relative number of particles in the condensates,
and there is a possibility to exchange the vortex states between condensates by
shifting the centers of the trapping potentials.Comment: 4 pages, 2 figure
Single electron charging of impurity sites visualized by scanning gate experiments on a quantum point contact
A quantum point contact (QPC) patterned on a two-dimensional electron gas is
investigated with a scanning gate setup operated at a temperature of 300 mK.
The conductance of the point contact is recorded while the local potential is
modified by scanning the tip. Single electron charging of impurities induced by
the local potential is observed as a stepwise conductance change of the
constriction. By selectively changing the state of some of these impurities, it
is possible to observe changes in transmission resonances of the QPC. The
location of such impurities is determined, and their density is estimated to be
below 50 per \mu m^2, corresponding to less than 1 % of the doping
concentration
Magnetic Field Induced Insulating Phases at Large
Exploring a backgated low density two-dimensional hole sample in the large
regime we found a surprisingly rich phase diagram. At the highest
densities, beside the , 2/3, and 2/5 fractional quantum Hall states,
we observe both of the previously reported high field insulating and reentrant
insulating phases. As the density is lowered, the reentrant insulating phase
initially strengthens, then it unexpectedly starts weakening until it
completely dissapears. At the lowest densities the terminal quantum Hall state
moves from to . The intricate behavior of the insulating
phases can be explained by a non-monotonic melting line in the -
phase space
Wigner crystallization and metal-insulator transition of two-dimensional holes in GaAs/AlGaAs at B=0
We report the transport properties of a low disorder two-dimensional hole
system (2DHS) in the GaAs/AlGaAs heterostructure, which has an unprecedentedly
high peak mobility of , with hole density of in the temperature range of
. From their T, p, and electric field dependences, we find that
the metal-insulator transition in zero magnetic field in this exceptionally
clean 2DHS occurs at , which is in good agreement with the
critical for Wigner crystallization , predicted by
Tanatar and Ceperley for an ideally clean 2D system.Comment: 4 pages, 4 Postscript figure
Binary Bose-Einstein Condensate Mixtures in Weakly and Strongly Segregated Phases
We perform a mean-field study of the binary Bose-Einstein condensate mixtures
as a function of the mutual repulsive interaction strength. In the phase
segregated regime, we find that there are two distinct phases: the weakly
segregated phase characterized by a `penetration depth' and the strongly
segregated phase characterized by a healing length. In the weakly segregated
phase the symmetry of the shape of each condensate will not take that of the
trap because of the finite surface tension, but its total density profile still
does. In the strongly segregated phase even the total density profile takes a
different symmetry from that of the trap because of the mutual exclusion of the
condensates. The lower critical condensate-atom number to observe the complete
phase segregation is discussed. A comparison to recent experimental data
suggests that the weakly segregated phase has been observed.Comment: minor change
Asymmetric Josephson Effect in Inversion Symmetry Breaking Topological Materials
Topological materials which possess topologically protected surface states
have attracted much attention in recent years. In this work, we study the
critical current of superconductor/inversion symmetry breaking topological
material/superconductor junctions. We found surprisingly that, in topological
materials with broken inversion symmetry, the magnitude of the critical
Josephson currents at fixed magnetic field is not the same
for critical currents flowing in the opposite direction.
Moreover, the critical currents violate the relation and give rise to asymmetric Fraunhofer patterns. We
call this phenomenon asymmetric Josephson effect (AJE). AJE can be use to
detect inversion symmetry breaking in topological materials such as in quantum
spin Hall systems and Weyl semimetals.Comment: 4+ pages, 4 figures. Comments are welcom
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