Jun 2017
Jun 1-Jun 10 Biao Huang, Jun 11-Jun 20 Haiyuan Zou, Jun 21-Jun 30 Zehan Li
Jun 12 arXiv:1706.03076 [pdf, ps, other] One-dimensional Repulsive Fermi Gas in a Tunable Periodic Potential Sebastiano Pilati, Luca Barbiero, Rosario Fazio, Luca Dell'Anna Comments: 6 pages, 5 figures Subjects: Quantum Gases (cond-mat.quant-gas) By using unbiased continuos-space quantum Monte Carlo simulations, we investigate the ground state properties of a one-dimensional repulsive Fermi gas subjected to a commensurate periodic optical lattice (OL) of arbitrary intensity. The equation of state and the magnetic structure factor are determined as a function of the interaction strength and of the OL intensity. In the weak OL limit, Yang's theory for the energy of a homogeneous Fermi gas is recovered. In the opposite limit (deep OL), we analyze the convergence to the Lieb-Wu theory for the Hubbard model, comparing two approaches to map the continuous-space to the discrete-lattice model: the first is based on (noninteracting) Wannier functions, the second effectively takes into account strong-interaction effects within a parabolic approximation of the OL wells. We find that strong antiferromagnetic correlations emerge in deep OLs, and also in very shallow OLs if the interaction strength approaches the Tonks-Girardeau limit. In deep OLs we find quantitative agreement with density matrix renormalization group calculations for the Hubbard model. The spatial decay of the antiferromagnetic correlations is consistent with quasi long-range order even in shallow OLs, in agreement with previous theories for the half-filled Hubbard model. Jun 19 arXiv:1706.05023 [pdf, ps, other] Optimal inhomogeneity for pairing in Hubbard systems with next-nearest-neighbor hopping Gideon Wachtel, Shirit Baruch, Dror Orgad Comments: 6 pages, 8 figuresSubjects: Superconductivity (cond-mat.supr-con)Previous studies have shown that bipartite Hubbard systems with inhomogeneous hopping amplitudes can exhibit higher pair-binding energies than the uniform model. Here we examine whether this result holds for systems with a more generic band structure. To this end, we use exact diagonalization and the density matrix renormalization group method to study the 4x4 Hubbard cluster and the two-leg Hubbard ladder with checkerboard-modulated nearest-neighbor hopping, t, and next-nearest-neighbor (diagonal) hopping, t_d. We find that the strongest pairing continues to occur at an intermediate level of inhomogeneity. While the maximal pair-binding energy is enhanced by a positive t_d/t, it is suppressed and appears at weaker repulsion strengths and smaller hole concentrations when t_d/t is negative. We point out a possible connection between the pairing maximum and the magnetic properties of the system.
