Superfluid phases of fermions with hybridized<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>s</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>p</mml:mi></mml:math>orbitals

Yin, Shaoyu; Baarsma, J. E.; Heikkinen, Mikko; Martikainen, Jani-Petri; Törmä, Païvi

doi:10.1103/physreva.92.053616

Cited by 19 publications

(20 citation statements)

References 41 publications

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“…At this time experiments are not yet conclusive on the question of a transition [17,18]. The existence and nature of such a transition impacts the overall phase diagram for spin-imbalanced 2D Fermi gas [28][29][30][31][32]. Some work using a variational approach did not show any ground-state transition [13].…”

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confidence: 99%

Ab initioLattice Results for Fermi Polarons in Two Dimensions

Bour¹,

Lee

Hammer

et al. 2015

Phys. Rev. Lett.

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We investigate the attractive Fermi polaron problem in two dimensions using non-perturbative Monte Carlo simulations. We introduce a new Monte Carlo algorithm called the impurity lattice Monte Carlo method. This algorithm samples the path integral in a computationally efficient manner and has only small sign oscillations for systems with a single impurity. As a benchmark of the method, we calculate the universal polaron energy in three dimensions in the scale-invariant unitarity limit and find agreement with published results. We then present the first fully non-perturbative calculations of the polaron energy in two dimensions and density correlations between the impurity and majority particles in the limit of zero range interactions. We find evidence for a smooth crossover transition from fermionic quasiparticle to molecular state as a function of interaction strength.PACS numbers: 67.85. Lm, 02.70.Ss, One of the most interesting and fundamental problems in quantum many-body physics is the polaron problem, where a mobile impurity interacts with a bath of particles. With the advent of trapped ultracold atomic gases, the polaron problem can now be realized for both bosonic and fermionic baths, and also in the universal limit where the range of the particle interactions are negligible [1]. In a fermionic medium, the impurity can undergo a transition and change its quantum statistics by binding fermions from the surrounding Fermi gas [2,3]. The impurity is dressed by fluctuations of the Fermi sea forming a quasiparticle or polaron state. But with increasing particle interaction strength, molecules will form by capturing one or even two particles from the Fermi sea, and this behavior has been shown to depend on the mass ratio of the two components of the Fermi gas for the 3D case [2][3][4][5][6][7][8][9][10]. In 1D, the exact analytical solution for equal masses shows that the polaron-molecule transition is a smooth crossover [11,12].In 2D the Fermi polaron properties have been studied using different theoretical and experimental approaches, and these have predicted various scenarios for the existence or absence of a polaron-molecule transition [13][14][15][16][17][18][19][20][21]. The Fermi polaron system has been studied using diagrammatic Monte Carlo (diag MC) [20,21]. The diag MC method uses a worm algorithm to stochastically sample Feynman diagrams to high orders in the coupling constant. In this work we introduce a non-perturbative ab initio approach called impurity lattice Monte Carlo (ILMC) [22] to investigate highlyimbalanced Fermi gases. Unlike diag MC, impurity lattice Monte Carlo directly samples the path integral and so is a fully non-perturbative calculation. We present calculations for the energy of the 2D polaron and density correlations between the impurity and majority particles as a function of interaction strength. Our results show evidence for a smooth crossover from polaron to molecule.Impurity lattice Monte Carlo method. The impurity lattice Monte Carlo method is a hybrid of two Monte Carlo al...

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confidence: 99%

Ab initioLattice Results for Fermi Polarons in Two Dimensions

Bour¹,

Lee

Hammer

et al. 2015

Phys. Rev. Lett.

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“…the Lieb lattice, was first proposed in [1] as a rigorous example of itinerant ferromagnetism in the presence of on-site Hubbard interactions at half-filling. Recently, the Lieb lattice received renewed attention in the context of optical and photonic lattices [2][3][4][5][6][7], 2D superconductivity [8,9], or for its specific topological properties [10][11][12][13][14][15]. In particular, the artificial lattice realization offers the advantage of parameters controlling, leading to various regimes not available in real-atoms lattices, so that one can test a vast spectrum of theoretical prediction.…”

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confidence: 99%

Ground state spin and excitation energies in half-filled Lieb lattices

Ţolea

Niţă

2016

Phys. Rev. B

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We present detailed spectral calculations for small Lieb lattices having up to N = 4 number of cells, in the regime of half-filling, an instance of particular relevance for the nano-magnetism of discrete systems such as quantum dot arrays, due to the degenerate levels at mid-spectrum. While for the Hubbard interaction model -and even number of sites-the ground state spin is given by the Lieb theorem, the inclusion of long range interaction -or odd number of sites-make the spin state not a priori known, which justifies our approach. We calculate also the excitation energies, which are of experimental importance, and find significant variation induced by the interaction potential. One obtains insights on the mechanisms involved that impose as ground state the Lieb state with lower spin rather than the Hund one with maximum spin for the degenerate levels, showing this in the first and second order of the interaction potential for the smaller lattices. The analytical results concorde with the numerical ones, which are performed by exact diagonalization calculations or by a combined mean-field and configuration interaction method. While the Lieb state is always lower in energy than the Hund state, for strong long-range interaction, when possible, another minimal spin state is imposed as ground state.

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“…Motivated by the recently discussed topological characters of multiband models 16,24 , and based on the simplest model that describes the topological properties of a chain of spinless fermions, we study the Kitaev model with two orbital-bands. We include and discuss inter-and intraband superconducting couplings.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, topological semimetals 26 and chiral superfluidity 27 have been predicted in multiorbital models where orbitals with different symmetries interact. Two component fermionic systems with occupied s and p orbital states were shown to have a rich phase diagram in both one and two dimensions 24 . A general connection between multiband and multicomponent superconductivity has also been made 28 .…”

Section: Introductionmentioning

confidence: 99%

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4π Josephson currents in junctions of hybridized multiband superconductors

2017

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We study two-band one-dimensional superconducting chains of spinless fermions with inter and intra-band pairing. These bands hybridize and, depending on the relative angular momentum of their orbitals, the hybridization can be symmetric or anti-symmetric. The self-consistent competition between intra and inter-band superconductivity and how it is affected by the symmetry of the hybridization is investigated. In the case of anti-symmetric hybridization the intra and inter-band pairings do not coexist while in the symmetric case they do coexist and the interband pairing is shown to be dominant. The topological properties of the model are obtained through the topological invariant winding number and the presence of edge states. We find the existence of a topological phase due to the inter-band superconductivity and induced by symmetric hybridization. In this case we find a characteristic 4π-periodic Josephson current. In the case of anti-symmetric hybridization we also find a 4π-periodic Josephson current in the gapless inter-band superconducting phase, recently identified to be of Weyl-type.

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Superfluid phases of fermions with hybridizedsandporbitals

Cited by 19 publications

References 41 publications

Ab initioLattice Results for Fermi Polarons in Two Dimensions

Ab initioLattice Results for Fermi Polarons in Two Dimensions

Ground state spin and excitation energies in half-filled Lieb lattices

4π Josephson currents in junctions of hybridized multiband superconductors

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