Yen Lee Loh

Single- and two-particle energy gaps across the disorder-driven superconductor–insulator transition

After decades of research, the microscopic details of the superconductor–insulator transition in two-dimensions, which is driven by the presence of disorder, are revealed by simulations. These include a phase transition from a gapped superconductor to a gapped insulator, for example.

Detecting the Elusive Larkin-Ovchinnikov Modulated Superfluid Phases for Imbalanced Fermi Gases in Optical Lattices

We show that Larkin-Ovchinnikov (LO) states with modulated superfluid order parameters have a considerably larger range of stability in a lattice than in the continuum. We obtain the phase diagram for the 3D cubic attractive Hubbard model with an unequal population of up and down fermions using the Bogoliubov-de Gennes fully self-consistent method. We find a strong modulation of the local polarization that should provide a distinct signature for detection of the LO phase. The shell structure in the presence of a trap generates singularities in the density at the phase boundaries and provide additional evidence for the LO phase. Depending on specific parameters, the LO ground state occurs over a large range of population imbalance, involving 80% of the atoms in the trap, and can exist up to an entropy s ∼ 0.5kB per fermion.

Fermions in 3D optical lattices: cooling protocol to obtain antiferromagnetism.

A major challenge in realizing antiferromagnetic and superfluid phases in optical lattices is the ability to cool fermions. We determine the equation of state for the 3D repulsive Fermi-Hubbard model as a function of the chemical potential, temperature, and repulsion using unbiased determinantal quantum Monte Carlo methods, and we then use the local density approximation to model a harmonic trap. We show that increasing repulsion leads to cooling but only in a trap, due to the redistribution of entropy from the center to the metallic wings. Thus, even when the average entropy per particle is larger than that required for antiferromagnetism in the homogeneous system, the trap enables the formation of an antiferromagnetic Mott phase.

Thermodynamics of Ising spins on the triangular kagome lattice: Exact analytical method and Monte Carlo simulations

A new class of two-dimensional magnetic materials

Dynamical Conductivity across the Disorder-Tuned Superconductor-Insulator Transition

{\mathrm{Cu}}_{9}{X}_{2}{(\mathrm{cpa})}_{6}\ensuremath{\cdot}x{\mathrm{H}}_{2}\mathrm{O}

Dimers on the triangular kagome lattice

(

Efficient algorithm for random-bond ising models in 2D

\mathrm{cpa}=2

Noise predictions for STM in systems with local electron nematic order

-carboxypentonic acid;

Frequency and temperature dependence of the optical conductivity of granular metals : A path-integral approach

X=\mathrm{F},\mathrm{Cl},\mathrm{Br}

Proposal for interferometric detection of the topological character of modulated superfluidity in ultracold Fermi gases

) was recently fabricated in which Cu sites form a triangular kagome lattice (TKL). As the simplest model of geometric frustration in such a system, we study the thermodynamics of Ising spins on the TKL using exact analytic method as well as Monte Carlo simulations. We present the free energy, internal energy, specific heat, entropy, sublattice magnetizations, and susceptibility. We describe the rich phase diagram of the model as a function of coupling constants, temperature, and applied magnetic field. For frustrated interactions in the absence of applied field, the ground state is a spin liquid phase with residual entropy per spin