Nonequilibrium and local detection of the normal fraction of a trapped two-dimensional Bose gas

Carusotto, Iacopo

doi:10.1103/physreva.84.053637

Cited by 10 publications

(13 citation statements)

References 80 publications

(130 reference statements)

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“…In fact, a quantitative measurement of the superfluid density is more generally an open question in the field of ultracold atomic gases. This is an active area of current research, 54,55 and one big hope is that in the near feature it will be possible to perform both types of measurements on identically prepared atomic samples, thus providing a direct experimental comparison of di↵erent theoretical definitions of superfluidity.…”

Section: Discussionmentioning

confidence: 99%

BKT Physics with Two-Dimensional Atomic Gases

Hadzibabic

Dalibard

2013

40 Years of Berezinskii–Kosterlitz–Thouless Theory

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In this chapter we review the recent advances in experimental investigation and theoretical understanding of Berezinskii-Kosterlitz-Thouless (BKT) physics in ultracold trapped atomic gases. We explain how to produce quasi two-dimensional (2D) samples by freezing out one degree of freedom with laser beams, and we detail the modelling of atomic interactions in this constrained geometry. We discuss some remarkable properties of the equation of state of dilute 2D Bose gases, such as its scale invariance. We also comment on the "competition" between the superfluid, BKT-driven phase transition in a homogenous 2D fluid of bosons, and the more conventional Bose-Einstein condensation that is expected for an ideal 2D Bose gas confined in a harmonic potential. We present some experimental techniques that allow one to measure the equation of state of the gas, monitor the occurrence of a BKT-driven phase transition, and observe thermally activated quantized vortices, which constitute the microscopic building block of the BKT mechanism.

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Section: Discussionmentioning

confidence: 99%

BKT Physics with Two-Dimensional Atomic Gases

Hadzibabic

Dalibard

2013

40 Years of Berezinskii–Kosterlitz–Thouless Theory

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“…Ho and Zhou [22] showed that the superfluid density can be extracted from images of rotating clouds. John, Hadzibabic and Cooper [23] identified a global spectroscopic measure of superfluidity, while Carusotto and Castin [24] investigated a local probe.…”

Section: Experimental Probes Of ρSmentioning

confidence: 99%

Superfluid Density of Weakly Interacting Bosons on a Lattice

Yanay,

Mueller

2012

Preprint

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We use a path integral approach to calculate the superfluid density of a Bose lattice gas in the limit where the number of atoms per site is large. Our analytical expressions agree with numerical results on small systems for low temperatures and relatively weak interactions. We also calculate the superfluid density and drag for two-component lattice bosons. To attain the correct results we develop tools for calculating discrete time path integrals. These tools should be broadly applicable to a range of systems which are naturally described within an overcomplete basis.

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“…Moreover, exploiting the polarization degree of freedom of polaritons, formation of spin domains [23] and half soliton trains [37][38][39] have been predicted. Finally, from a more general perspective, as the response of a quantum fluid to a phase perturbation is quantitatively related to its superfluid fraction [20,40,41], our experiment opens the way to the experimental measurement of this quantity, crucial in the theory of driven dissipative quantum fluids [42].…”

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confidence: 99%

Phase-Controlled Bistability of a Dark Soliton Train in a Polariton Fluid

et al. 2016

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We use a one-dimensional polariton fluid in a semiconductor microcavity to explore the rich nonlinear dynamics of counter-propagating interacting Bose fluids. The intrinsically driven-dissipative nature of the polariton fluid allows to use resonant pumping to impose a phase twist across the fluid. When the polariton-polariton interaction energy becomes comparable to the kinetic energy, linear interference fringes transform into a train of solitons. A novel type of bistable behavior controlled by the phase twist across the fluid is experimentally evidenced.Dark solitons are among the fundamental nonlinear collective excitations of one-dimensional (1D) quantum degenerate fluids with positive mass and repulsive interactions. They are characterized by a dip in a uniform background density and a jump in the macroscopic phase across it. The shape and size of the dip is given by the interplay of mass and nonlinearity. Because of the universality of the mechanisms necessary to their formation, dark solitons have been observed in a wide variety of systems ranging from Bose-Einstein condensates of cold atoms [1][2][3], optical fibers [4], to thin magnetic films [5]. Interestingly, dark solitons have also been observed in nonlinear open-dissipative systems, in particular, in semiconductor microcavities [6][7][8][9] and are attracting great interest in view of photonic applications [10].Semiconductor microcavities have recently appeared as an excellent platform to study the nonlinear dynamics of interacting Bose fluids in a photonic context [11]. Their elementary excitations are exciton-polaritons, bosonic quasiparticles arising from the strong coupling between quantum well excitons and photons confined in the microcavity. While their excitonic component provides significant repulsive interactions, the fast escape of photons out of the microcavity makes polaritons an intrinsically open-dissipative system, requiring continuous wave pumping to achieve a steady state. A number of quantum fluid effects have been studied in semiconductor microcavities, including superfluidity [12], diffusive Goldstone modes [13], Bogoliubov excitation spectrum [14], solitary bright waves [15,16], and the hydrodynamic nucleation of quantized vortices [17,18] and dark solitons [7,8].In addition to the possibility of in-situ and timeresolved imaging of the fluid dynamics, a remarkable feature of driven-dissipative systems is that a resonant drive allows setting the local phase of the wavefunction [11]. It is then possible to externally manipulate the boundary conditions and impose a controlled phase pattern across a polariton fluid. This was first explored in a two-dimensional polariton condensate in which a spatial vortex phase profile was imposed on the polariton field, resulting in persistent currents with high orbital momentum [19]. This technique opens up a new world for the exploration of the elementary excitations of polariton quantum fluids. In particular, it has been proposed that by imposing a phase twist across the fluid via the external...

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Nonequilibrium and local detection of the normal fraction of a trapped two-dimensional Bose gas

Cited by 10 publications

References 80 publications

BKT Physics with Two-Dimensional Atomic Gases

BKT Physics with Two-Dimensional Atomic Gases

Superfluid Density of Weakly Interacting Bosons on a Lattice

Phase-Controlled Bistability of a Dark Soliton Train in a Polariton Fluid

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