7,864 research outputs found
Radio-frequency dressed atoms beyond the linear Zeeman effect
We evaluate the impact that nonlinear Zeeman shifts have on resonant radio-frequency (RF) dressed traps in an atom-chip configuration. The degeneracy of the resonance between Zeeman levels is lifted at large intensities of a static field, modifying the spatial dependence of the atomic adiabatic potential. In this context, we find effects that are important for the next generation of atom chips with tight trapping: in particular, that the vibrational frequency of the atom trap is sensitive to the RF frequency and, depending on the sign of the Landé factor, can produce significantly weaker, or tighter trapping when compared to the linear regime of the Zeeman effect. We take 87 Rb as an example and find that it is possible for the trapping frequency on F = 1 to exceed that of the F = 2 hyperfine manifold
Floquet Fractional Chern Insulator in Doped Graphene
Fractional Chern insulators are theoretically predicted states of electronic
matter with emergent topological order. They exhibit the same universal
properties as the fractional quantum Hall effect, but dispose of the need to
apply a strong magnetic field. However, despite intense theoretical work, an
experimental realization for these exotic states of matter is still lacking.
Here we show that doped graphene turns into a fractional Chern insulator, when
irradiated with high-intensity circularly polarized light. We derive the
effective steady state band structure of light-driven graphene using Floquet
theory and subsequently study the interacting system with exact numerical
diagonalization. The fractional Chern insulator state equivalent to the 1/3
Laughlin state appears at 7/12 total filling of the honeycomb lattice (1/6
filling of the upper band). The state also features spontaneous ferromagnetism
and is thus an example of the spontaneous breaking of a continuous symmetry
along with a topological phase transition.Comment: 10 page
A semi-infinite matrix analysis of the BFKL equation
The forward BFKL equation is discretised in virtuality space and it is shown
that the diffusion into infrared and ultraviolet momenta can be understood in
terms of a semi-infinite matrix. The square truncation of this matrix can be
exponentiated leading to asymptotic eigenstates sharing many features with the
BFKL gluon Green's function in the limit of large matrix size. This truncation
is closely related to a representation of the XXX Heisenberg spin chain with SL(2) invariance where the Hamiltonian acts on a
symmetric double copy of the harmonic oscillator. A simple modification of the
BFKL matrix suppressing the infrared modes generates evolution with energy
compatible with unitarity.Comment: Small changes, same conclusions, matching the published version in
EPJ
Atom chips with two-dimensional electron gases: theory of near surface trapping and ultracold-atom microscopy of quantum electronic systems
We show that current in a two-dimensional electron gas (2DEG) can trap
ultracold atoms m away with orders of magnitude less spatial noise than
a metal trapping wire. This enables the creation of hybrid systems, which
integrate ultracold atoms with quantum electronic devices to give extreme
sensitivity and control: for example, activating a single quantized conductance
channel in the 2DEG can split a Bose-Einstein condensate (BEC) for atom
interferometry. In turn, the BEC offers unique structural and functional
imaging of quantum devices and transport in heterostructures and graphene.Comment: 5 pages, 4 figures, minor change
Population bound effects on bosonic correlations in non-inertial frames
We analyse the effect of bounding the occupation number of bosonic field
modes on the correlations among all the different spatial-temporal regions in a
setting in which we have a space-time with a horizon along with an inertial
observer. We show that the entanglement between A (inertial observer) and R
(uniformly accelerated observer) depends on the bound N, contrary to the
fermionic case. Whether or not decoherence increases with N depends on the
value of the acceleration a. Concerning the bipartition A-antiR (Alice with an
observer in Rindler's region IV), we show that no entanglement is created
whatever the value of N and a. Furthermore, AR entanglement is very quickly
lost for finite N and for infinite N. We will study in detail the mutual
information conservation law found for bosons and fermions. By means of the
boundary effects associated to N finiteness, we will show that for bosons this
law stems from classical correlations while for fermions it has a quantum
origin. Finally, we will present the strong N dependence of the entanglement in
R-antiR bipartition and compare the fermionic cases with their finite N bosonic
analogs. We will also show the anti-intuitive dependence of this entanglement
on statistics since more entanglement is created for bosons than for their
fermion counterparts.Comment: revtex 4, 12 pages, 10 figures. Added Journal ref
Nonholonomic constraints in -symplectic Classical Field Theories
A -symplectic framework for classical field theories subject to
nonholonomic constraints is presented. If the constrained problem is regular
one can construct a projection operator such that the solutions of the
constrained problem are obtained by projecting the solutions of the free
problem. Symmetries for the nonholonomic system are introduced and we show that
for every such symmetry, there exist a nonholonomic momentum equation. The
proposed formalism permits to introduce in a simple way many tools of
nonholonomic mechanics to nonholonomic field theories.Comment: 27 page
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