Exotic paired phases in ladders with spin-dependent hopping

Journal Article · Tue Mar 15 04:00:00 EDT 2011 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.83.115104· OSTI ID:21538188

Feiguin, Adrian E; Fisher, Matthew P. A. ^[1]

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1. Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071 (United States)

Fermions in two dimensions, when subject to anisotropic spin-dependent hopping, can potentially give rise to unusual paired states in unpolarized mixtures that can behave as non-Fermi liquids. One possibility is a fully paired state with a gap for fermion excitations in which the Cooper pairs remain uncondensed. Such a ''Cooper-pair Bose-metal'' phase would be expected to have a singular Bose surface in momentum space. As demonstrated in the context of two-dimensional bosons hopping with a frustrating ring-exchange interaction, an analogous Bose-metal phase has a set of quasi-one-dimensional descendant states when put on a ladder geometry. Here we present a density matrix renormalization group study of the attractive Hubbard model with spin-dependent hopping on a two-leg ladder geometry. In our setup, one spin species moves preferentially along the leg direction, while the other does so along the rung direction. We find compelling evidence for the existence of a novel Cooper-pair Bose-metal phase in a region of the phase diagram at intermediate coupling. We further explore the phase diagram of this model as a function of hopping anisotropy, density, and interaction strength, finding a conventional superfluid phase as well as a phase of paired Cooper pairs with d-wave symmetry, similar to the one found in models of hard-core bosons with ring exchange. We argue that simulating this model with cold Fermi gases on spin-dependent optical lattices is a promising direction for realizing exotic quantum states.

• OSTI ID: 21538188
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 11 Vol. 83; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANGULAR MOMENTUM
ANISOTROPY
COOPER PAIRS
COUPLING
CRYSTAL MODELS
D WAVES
DENSITY
DENSITY MATRIX
DIAGRAMS
ELEMENTS
ENERGY-LEVEL TRANSITIONS
EXCHANGE INTERACTIONS
EXCITATION
FERMI GAS
HUBBARD MODEL
INFORMATION
INTERACTIONS
INTERMEDIATE COUPLING
MATHEMATICAL MODELS
MATRICES
METALS
ONE-DIMENSIONAL CALCULATIONS
PARTIAL WAVES
PARTICLE PROPERTIES
PHASE DIAGRAMS
PHYSICAL PROPERTIES
QUANTUM STATES
RENORMALIZATION
SPIN
SUPERFLUIDITY
SURFACES
SYMMETRY
TWO-DIMENSIONAL CALCULATIONS