Density-functional theory for the crystalline phases of a two-dimensional dipolar Fermi gas

Zyl, Brandon P. van; Kirkby, W.; Ferguson, W. G.

doi:10.1103/physreva.92.023614

Cited by 12 publications

(29 citation statements)

References 28 publications

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“…With a self-consistent solution of the gap and number equations, we have compared the interlayer superfluidity in the unscreened case with the NS and the SS ones. We have observed that within our NS scheme the bilayer system becomes unstable towards the density wave instability at small layer spacings, in agreement with many similar studies [39][40][41]. But once the effects of interlayer pairing are included in the screening this instability goes away.…”

Section: Discussionsupporting

confidence: 91%

Interplay of interlayer pairing and many-body screening in a bilayer of dipolar fermions

Mazloom¹,

Abedinpour²

2018

Phys. Rev. B

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In a bilayer system of fermionic dipoles, a full control over the strength of the attractive interactions between two layers leads to the BCS-BEC crossover. Here, using the BCS mean field theory, we study such a crossover in symmetric bilayers of ultracold dipolar fermions with their dipole moments being perpendicular to layers. In particular, we investigate how the pairing between two layers and the many-body screening of interlayer interaction affect each other. We compare results for pairings obtained with three different approximations for the interlayer interactions namely, bare dipoledipole interaction, the random-phase approximation for screening obtained in the normal phase, and the self-consistent superfluid phase screening within the random-phase approximation. We find that at weak couplings the screening further suppresses the pairing while at strong couplings, the screening would be suppressed due to the pairing gap in the quasi-particle spectrum. Therefore a self-consistent treatment of both screening and pairing on equal footings is necessary for obtaining a correct picture of the phase diagram and order parameter at both small and large layer spacings and densities. We also notice that the highly speculated density-wave instability in bilayers with the parallel polarization of dipoles in two layers is simply an artifact of the incorrect screening scheme.

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Section: Discussionsupporting

confidence: 91%

Interplay of interlayer pairing and many-body screening in a bilayer of dipolar fermions

Mazloom¹,

Abedinpour²

2018

Phys. Rev. B

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“…Therefore inhomogeneous density phases such as density waves or quantum droplets [31] would be naturally expected in this regime. Here, we should mention that the density-wave instability within different approximations has been also predicted for ultracold dipolar systems with anisotropic dipole-dipole interaction [32][33][34][35] as well as in layered dipolar structures [36][37][38]. However, its emergence in a single-layer system, with a purely isotropic dipole-dipole interaction has been the subject of much dispute [39,40].…”

Section: Discussionmentioning

confidence: 99%

Phase diagram and dynamics of Rydberg-dressed fermions in two dimensions

2017

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We investigate the ground-state properties and the collective modes of a two-dimensional twocomponent Rydberg-dressed Fermi liquid in the dipole-blockade regime. We find instability of the homogeneous system toward phase separated and density ordered phases, using the Hartree-Fock and random-phase approximations, respectively. The spectral weight of collective density oscillations in the homogenous phase also signals the emergence of density-wave instability. We examine the effect of exchange-hole on the density-wave instability and on the collective mode dispersion using the Hubbard local-field factor. arXiv:1706.03222v1 [cond-mat.quant-gas]

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“…While the stripe or density-wave phase is naturally expected in an isolated two-dimensional (2D) system of tilted dipolar bosons [21,22] and fermions [23][24][25][26][27][28][29] due to the anisotropy of the dipole-dipole interaction, this instability has been the subject of much dispute in the limit of perpendicular dipoles, where the inter-particle interaction is isotropic. While mean-field approximation [23] as well as density-functional theory (DFT) [30] and Singwi-Tosi-Land-Sjölander (STLS) [25] calculations all predict stripe phase formation at relatively low interaction strength for 2D dipolar fermions, quantum Monte Carlo (QMC) simulations suggest that the stripe phase never becomes energetically favorable, up to the liquid-to-solid phase transition for perpendicular bosons [22] and fermions [31].…”

Section: Introductionmentioning

confidence: 99%

Density-wave instability and collective modes in a bilayer system of antiparallel dipoles

2018

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We consider a bilayer of dipolar particles in which the polarization of dipoles is perpendicular to the planes, in the antiparallel configuration. Using accurate static structure factor ( ) S q data from hypernetted-chain (HNC) and Fermi HNC calculations, respectively for an isolated layer of dipolar bosons and dipolar fermions, we construct effective screened intralayer interactions. Adopting the random-phase approximation for interlayer interactions, we investigate the instability of these homogeneous bilayer systems towards the formation of density waves by studying the poles of the density-density response function. We have also studied the collective modes of these systems and find that the dispersion of their antisymmetric collective mode signals the emergence of the density wave instability as well.

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Density-functional theory for the crystalline phases of a two-dimensional dipolar Fermi gas

Cited by 12 publications

References 28 publications

Interplay of interlayer pairing and many-body screening in a bilayer of dipolar fermions

Interplay of interlayer pairing and many-body screening in a bilayer of dipolar fermions

Phase diagram and dynamics of Rydberg-dressed fermions in two dimensions

Density-wave instability and collective modes in a bilayer system of antiparallel dipoles

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