64,009 research outputs found
su(2) and su(1,1) displaced number states and their nonclassical properties
We study su(2) and su(1,1) displaced number states. Those states are
eigenstates of density-dependent interaction systems of quantized radiation
field with classical current. Those states are intermediate states
interpolating between number and displaced number states. Their photon number
distribution, statistical and squeezing properties are studied in detail. It is
show that these states exhibit strong nonclassical properties.Comment: 10 pages, 3 figure
Renormalization Group Study of the Electron-phonon Interaction in the High Tc Cuprates
We generalize the numerical renormalization group scheme to study the
phonon-mediated retarded interactions in the high Tc cuprates. We find that
three sets of phonon-mediated retarded quasiparticle scatterings grow under RG
flow. These scatterings share the following common features: 1) the initial and
final quasiparticle momenta are in the antinodal regions, and 2) the scattering
amplitudes have a symmetry. All three sets of retarded interaction
are driven to strong coupling by the magnetic fluctuations around .
After growing strong, these retarded interaction will trigger density wave
orders with d-wave symmetry. However, due to the d-wave form factor they will
leave the nodal quasiparticle unaffected. We conclude that the main effect of
electron-phonon coupling in the cuprates is to promote these density wave
orders.Comment: 4 pages, 3 figures, references added, added more details about
others' previous studie
Influence of rotational instability on the polarization structure of SrTiO3
The k-space polarization structure and its strain response in SrTiO3 with
rotational instability are studied using a combination of first-principles
density functional calculations, modern theory of polarization, and analytic
Wannier-function formulation. (1) As one outcome of this study, we rigorously
prove-both numerically and analytically-that folding effect exists in
polarization structure. (2) After eliminating the folding effect, we find that
the polarization structure for SrTiO3 with rotational instability is still
considerably different from that for non-rotational SrTiO3, revealing that
polarization structure is sensitive to structure distortion of oxygen-octahedra
rotation and promises to be an effective tool for studying material properties.
(3) Furthermore, from polarization structure we determine the microscopic
Wannier-function interactions in SrTiO3. These interactions are found to vary
significantly with and without oxygen-octahedra rotation.Comment: 25 pages, 7 figure
Intersection theory and the Alesker product
Alesker has introduced the space of {\it smooth
valuations} on a smooth manifold , and shown that it admits a natural
commutative multiplication. Although Alesker's original construction is highly
technical, from a moral perspective this product is simply an artifact of the
operation of intersection of two sets. Subsequently Alesker and Bernig gave an
expression for the product in terms of differential forms. We show how the
Alesker-Bernig formula arises naturally from the intersection interpretation,
and apply this insight to give a new formula for the product of a general
valuation with a valuation that is expressed in terms of intersections with a
sufficiently rich family of smooth polyhedra.Comment: further revisons, now 23 page
Transition to the Giant Vortex State in an Harmonic Plus Quartic Trap
We consider a rapidly rotating Bose-condensed gas in an harmonic plus quartic
trap. At sufficiently high rotation rates the condensate acquires an annular
geometry with the superposition of a vortex lattice. With increasing rotation
rate the lattice evolves into a single ring of vortices. Of interest is the
transition from this state to the giant vortex state in which the circulation
is carried by only a central vortex. By analyzing the Gross-Pitaevskii energy
functional variationally, we have been able to map out the phase boundary
between these two states as a function of the rotation rate and the various
trapped gas parameters. The variational results are in good qualitative
agreement with those obtained by means of a direct numerical solution of the
Gross-Pitaevskii equation.Comment: 19 pages, 10 figure
Bulk Entanglement Spectrum Reveals Quantum Criticality within a Topological State
A quantum phase transition is usually achieved by tuning physical parameters
in a Hamiltonian at zero temperature. Here, we demonstrate that the ground
state of a topological phase itself encodes critical properties of its
transition to a trivial phase. To extract this information, we introduce a
partition of the system into two subsystems both of which extend throughout the
bulk in all directions. The resulting bulk entanglement spectrum has a
low-lying part that resembles the excitation spectrum of a bulk Hamiltonian,
which allows us to probe a topological phase transition from a single
wavefunction by tuning either the geometry of the partition or the entanglement
temperature. As an example, this remarkable correspondence between topological
phase transition and entanglement criticality is rigorously established for
integer quantum Hall states.Comment: 5 pages, 2 figures, 3 pages of Supplementary Materia
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