3,507 research outputs found
Momentum-space Aharonov-Bohm interferometry in Rashba spin-orbit coupled Bose-Einstein condensates
Since the recent experimental realization of synthetic Rashba spin-orbit
coupling paved a new avenue for exploring and engineering topological phases in
ultracold atoms, a precise, solid detection of Berry phase has been desired for
unequivocal characterization of system topology. Here, we propose a scheme to
conduct momentum-space Aharonov-Bohm interferometry in a Rashba spin-orbit
coupled Bose-Einstein condensate with a sudden change of in-plane Zeeman field,
capable of measuring the Berry phase of Rashba energy bands. We find that the
Berry phase with the presence of a Dirac point is directly revealed by a robust
dark interference fringe, and that as a function of external Zeeman field is
characterized by the contrast of fringes. We also build a variational model
describing the interference process with semiclassical equations of motion of
essential dynamical quantities, which lead to agreeable trajectories and
geometric phases with the real-time simulation of Gross-Pitaevskii equation.
Our study would provide timely guidance for the experimental detection of Berry
phase in ultracold atomic systems and help further investigation on their
interference dynamics in momentum space.Comment: 9 pages, 6 figure
Ground-state phase diagram of an anisotropic spin- model on the triangular lattice
Motivated by the recent experiment on a rare-earth material YbMgGaO [Y.
Li \textit{et al.}, Phys. Rev. Lett. \textbf{115}, 167203 (2015)], which found
that the ground state of YbMgGaO is a quantum spin liquid, we study the
ground-state phase diagram of an anisotropic spin- model that was proposed
to describe YbMgGaO. Using the density-matrix renormalization group method
in combination with the exact diagonalization, we calculate a variety of
physical quantities, including the ground-state energy, the fidelity, the
entanglement entropy and spin-spin correlation functions. Our studies show that
in the quantum phase diagram there is a phase and two distinct
stripe phases. The transitions from the two stripe phases to the
phase are of the first order. However, the transition between the two stripe
phases is not the first order, which is different from its classical
counterpart. Additionally, we find no evidence for a quantum spin liquid in
this model. Our results suggest that additional terms may be also important to
model the material YbMgGaO. These findings will stimulate further
experimental and theoretical works in understanding the quantum spin liquid
ground state in YbMgGaO.Comment: minor change
Non-Hermitian Disorder-induced Topological insulators
Recent studies of disorder or non-Hermiticity induced topological insulators
inject new ingredients for engineering topological matter. Here we consider the
effect of purely non-Hermitian disorders, a combination of these two
ingredients, in a 1D chiral symmetric lattice with disordered gain and loss.
The increasing disorder strength can drive a transition from trivial to
topological insulators, characterizing by the change of topological winding
number defined by localized states in the gapless and complex bulk spectra. The
non-Hermitian critical behaviors are characterized by the biorthogonal
localization length of zero energy edge modes, which diverges at the critical
transition point and establishes the bulk-edge correspondence. Furthermore, we
show that the bulk topology may be experimentally accessed by measuring the
biorthogonal chiral displacement , which converges to the winding
number through time-averaging and can be extracted from proper
Ramsey-interference sequences. We propose a scheme to implement and probe such
non-Hermitian disorder driven topological insulators using photons in coupled
micro-cavities.Comment: 4 pages, 5 figures and Supplementary Material
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