28 research outputs found
Multi-particle composites in density-imbalanced quantum fluids
We consider two-component one-dimensional quantum gases with density
imbalance. While generically such fluids are two-component Luttinger liquids,
we show that if the ratio of the densities is a rational number, p/q, and mass
asymmetry between components is sufficiently strong, one of the two eigenmodes
acquires a gap. The gapped phase corresponds to (algebraic) ordering of
(p+q)-particle composites. In particular, for attractive mixtures, this implies
that the superconducting correlations are destroyed. We illustrate our
predictions by numerical simulations of the fermionic Hubbard model with
hopping asymmetry.Comment: 4+ pages, 1 figure, published versio
Luttinger liquid of trimers in Fermi gases with unequal masses
We investigate one dimensional attractive Fermi gases in spin-dependent
optical lattices. We show that three-body bound states - "trimers" - exist as
soon as the two tunneling rates are different. We calculate the binding energy
and the effective mass of a single trimer. We then show numerically that for
finite and commensurate densities an energy gap
appears, implying that the gas is a one-component Luttinger liquid of trimers
with suppressed superfluid ordering. The boundaries of this novel phase are
given. We discuss experimental situations to test our predictions.Comment: 4 pages, 4 figures. Final accepted versio
Superfluid Interfaces in Quantum Solids
One scenario for the non-classical moment of inertia of solid He-4 discovered
by Kim and Chan [Nature 427, 225 (2004)] is the superfluidity of
micro-crystallite interfaces. On the basis of the most simple model of a
quantum crystal--the checkerboard lattice solid--we show that the superfluidity
of interfaces between solid domains can exist in a wide range of parameters. At
strong enough inter-particle interaction, a superfluid interface becomes an
insulator via a quantum phase transition. Under the conditions of particle-hole
symmetry, the transition is of the standard U(1) universality class in 3D,
while in 2D the onset of superfluidity is accompanied by the interface
roughening, driven by fractionally charged topological excitations.Comment: 4 revtex4 page
High Precision Measurement of the Thermal Exponent for the Three-Dimensional XY Universality Class
Simulations results are reported for critical point of the two-component
field theory. The correlation length exponent is measured to high
precision with the result . This value is in agreement with
recent simulation results [Campostrini \textit{et al}., Phys. Rev. B
\textbf{63}, 214503 (2001)], and marginally agrees with the most recent
space-based measurements of the superfluid transition in He [Lipa
\textit{et al}., Phys. Rev. B \textbf{68}, 174518 (2003)].Comment: a reference adde
The impact of the injection protocol on an impurity's stationary state
We examine stationary state properties of an impurity particle injected into
a one-dimensional quantum gas. We show that the value of the impurity's end
velocity lies between zero and the speed of sound in the gas, and is determined
by the injection protocol. This way, the impurity's constant motion is a
dynamically emergent phenomenon whose description goes beyond accounting for
the kinematic constraints of Landau approach to superfluidity. We provide exact
analytic results in the thermodynamic limit, and perform finite-size numerical
simulations to demonstrate that the predicted phenomena are within the reach of
the existing ultracold gases experiments.Comment: main text+supplemental, 14 pages, 3 figures; v2: title, introduction,
and summary modified, 3 refs. adde
Dimensional crossover on multileg attractive- Hubbard ladders
We study the ground state properties of a polarized two-component Fermi gas
on multileg attractive- Hubbard ladders. Using exact diagonalization and
density matrix renormalization group method simulations, we construct grand
canonical phase diagrams for ladder widths of up to and varying
perpendicular geometries, characterizing the quasi-one-dimensional regime of
the dimensional crossover. We unveil a multicritical point marking the onset of
partial polarization in those phase diagrams, a candidate regime of
finite-momentum pairing. We compare our findings with recent experimental and
theoretical studies of quasi-one-dimensional polarized Fermi gases.Comment: 6 pages, 5 figure