Momentum-Space Josephson Effects

Hou, Jue; Luo, Xi-Wang; Sun, Kuei; Bersano, Thomas; Gokhroo, Vandna; Mossman, Sean; Engels, Peter; Zhang, Chuanwei

doi:10.1103/physrevlett.120.120401

Cited by 31 publications

(32 citation statements)

References 60 publications

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“…In order to understand the origin of this degeneracy we look into the distribution of the tunneling current initiated by these excitations. The transverse tunneling current density can be written in the following form Inserting here the wave function (12,13) we get…”

Section: General Properties Of the Bogoliubov Spectrummentioning

confidence: 99%

“…These effects have been initially studied for coupled condensates in double-well traps [1][2][3][4][5][6] and coherently coupled spinor condensates [7,8]. In recent years Josephson effects were also observed and analyzed in more exotic systems such as fermionic superfluids [9], polariton condensates [10], spin-orbit coupled BECs [11,12] and condensates with attractive interaction [13].…”

Section: Introductionmentioning

confidence: 99%

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Collective excitations and tunneling dynamics in long bosonic Josephson junctions

2019

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We investigate the low-energy dynamics of two coupled anisotropic Bose-Einstein condensates forming a long Josephson junction. The theoretical study is performed in the framework of the two-dimensional Gross-Pitaevskii equation and the Bogoliubov-de Gennes formalism. We analyze the excitation spectrum of the coupled Bose condensates and show how low-energy excitations of the condensates lead to multiple-frequency oscillations of the atomic populations in the two wells. This analysis generalizes the standard bosnic Josephson euqation approach. We also develop a one-dimensional hydrodynamic model of the coupled condensates, that is capable to reproduce the excitation spectrum and population dynamics of the system.

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Section: General Properties Of the Bogoliubov Spectrummentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Collective excitations and tunneling dynamics in long bosonic Josephson junctions

2019

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“…The Rabi oscillations shown here are driven by a weak lattice which is slightly stronger than the mean field interaction strength. This character may be indicative of the dynamics underlying momentum-space Josephson junctions [37], which is beyond the scope of these experimental observations.Stripe-phase ground state stability. While previous arguments have indicated that we reliably prepare the appropriate spin-momentum mixtures to achieve a highcontrast stripe-phase, those mixtures must be coherent over a long period of time to produce the expected density modulation for further investigation of dynamical 0.0 0.5 1.0 1.5 2.0 Time after quench [ms] −1.0 −0.5 0.0 0.5…”

mentioning

confidence: 94%

“…However, recent works have attempted to sidestep these difficulties in creative ways, leading to experimental observations of some signatures of superfluid stripe phases in different systems [31][32][33][34].Despite these significant advances, the quest for a robust and long-lived platform for the experimental investigations of stripe-phase properties remains. In this Letter, we show that the superposition of two local band minima to form a supersolid-like ground state can be robustly achieved by means other than atomic interactions.Specifically, we engineer momentum-space hopping between two local band minima in a SOC BEC driven by a weak optical lattice [35][36][37]. The coupling between different momenta through static or moving optical lattices has been widely used in ultracold atomic gases for engineering versatile types of physics [38][39][40][41], but momentum states involved in such coupling schemes are usually not local band minima and thus have short lifetime.…”

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confidence: 99%

Experimental realization of a long-lived striped Bose-Einstein condensate induced by momentum-space hopping

et al. 2019

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In the past few decades, the search for supersolid-like phases has attracted great attention in condensed matter and ultracold atom communities. Here we experimentally demonstrate a route for realizing a superfluid stripe-phase in a spin-orbit coupled Bose-Einstein condensate by employing a weak optical lattice to induce momentum-space hopping between two spin-orbit band minima. We characterize the striped ground state as a function of lattice coupling strength and spin-orbit detuning and find good agreement with mean-field simulations. We observe coherent Rabi oscillations in momentum space between two band minima and demonstrate a long lifetime of the ground state. Our work offers an exciting new and stable experimental platform for exploring superfluid stripe-phases and their exotic excitations, which may shed light on the properties of supersolid-like states.Introduction. Supersolids are an exotic phase of matter which simultaneously possess the crystalline properties of a solid and the unique flow properties of a superfluid [1]. Such simultaneous breaking of continuous translational symmetry and U(1) gauge symmetry was first predicted for solid helium [2,3], but convincing evidence of a supersolid state in this system has remained elusive [4]. In recent years, the experimental realization of spin-orbit coupling (SOC) in ultracold atomic gases [5][6][7][8][9][10][11][12][13][14][15][16][17] has opened a new pathway for demonstrating long-sought supersolidlike states [18][19][20][21][22][23][24][25][26][27][28][29][30].The lowest energy band in the SOC dispersion is characterized by two local minima at distinct momenta [5]. For a narrow range of system parameters, mean-field interactions within a Bose-Einstein condensate (BEC) favor a ground state which is composed of a coherent superposition of two plane-wave states at the dispersion minima [22]. This superposition leads to density modulations in real space, or stripes, therefore breaking translational symmetry while maintaining the superfluid phase correlation of a BEC. Such a stripe-phase was initially proposed for SOC BECs where the pseudospins are defined by two atomic hyperfine states [5]. While great experimental progress has been made in exploring the rich physics of such SOC systems, a ground state superfluid stripe-phase has not been observed in this context. The necessary parameter space is prohibitively sensitive to magnetic field fluctuations and the resulting density modulation is weak. However, recent works have attempted to sidestep these difficulties in creative ways, leading to experimental observations of some signatures of superfluid stripe phases in different systems [31][32][33][34].Despite these significant advances, the quest for a robust and long-lived platform for the experimental investigations of stripe-phase properties remains. In this Letter, we show that the superposition of two local band minima to form a supersolid-like ground state can be robustly achieved by means other than atomic interactions.Specifically, we engineer momen...

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“…This has opened a whole new research field of strongly correlated systems with potential applications in quantum technology and quantum simulation of condensed-matter problems [4][5][6][7][8]. One such well-studied example is the system of a few interacting bosons in a double-well potential [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].BEC in a symmetric double-well potential, popularly known as the bosonic Josephson junction (BJJ) [29], provides a paradigm model which is used to study many fundamental quantum features like quantum entanglement [30], and to construct atom interferometers such as a Mach-Zehnder interferometer [31]. BJJ dynamics has been studied quite thoroughly both theoretically and experimentally [9-13, 19, 22, 29, 32-50].…”

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confidence: 99%

Many-body quantum dynamics of an asymmetric bosonic Josephson junction

Haldar

Alon

2019

New J. Phys.

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The out-of-equilibrium quantum dynamics of an interacting Bose gas trapped in a one-dimensional asymmetric double-well potential is studied by solving the many-body Schrödinger equation numerically accurately. We examine how the gradual loss of symmetry of the confining trap affects the macroscopic quantum tunneling dynamics of the system between the two wells. In an asymmetric double well, the two wells are not equivalent anymore, say, the left well is deeper than the right one. Accordingly, we analyze the dynamics by initially preparing the condensate in both the left and the right wells. The dynamics of the system is characterized by the time evolution of a few physical quantities of increasing many-body complexity, namely, the survival probability, depletion and fragmentation, and the many-particle position and momentum variances. In particular, we have examined the frequencies and amplitudes of the oscillations of the survival probabilities, the time scale for the development of fragmentation and its degree, and the growth and oscillatory behavior of the many-particle position and momentum variances. There is an overall suppression of the oscillations of the survival probabilities in an asymmetric double well, except for resonant values of asymmetry for which the one-body ground state energy in the right well matches with one of the one-body excited states in the left well, thereby resulting in resonantly enhanced tunneling from the right well ground state. Overall, depending on whether the condensate is initially prepared in the left or right well, the repulsive inter-atomic interactions affect the survival probabilities differently. For a sufficiently strong repulsive interaction, the system is found to become fragmented. The degree of fragmentation depends both on the asymmetry of the trap and the initial well in which the condensate is prepared in a non-trivial manner. Furthermore, we show that the phenomenon of resonantly enhanced tunneling can be accompanied by a large degree of fragmentation (depletion) for the strong (weak) interaction. The many-particle position and momentum variances follow the density oscillations of the system in the asymmetric double well and bears prominent signatures of the degree of depletion or fragmentation, depending on the strength of the interactions. These quantities further exhibit a fine structure signifying a breathing-mode oscillation. Finally, a universality of fragmentation for systems made of different numbers of particles but the same interaction parameter is also found and its dependence on the asymmetry is investigated. The phenomenon is robust despite the asymmetry of the junction and admits a macroscopically-large fragmented condensate characterized by a diverging many-particle position variance. This is as far as one can get from the dynamics of the density in the junction.recently. This has opened a whole new research field of strongly correlated systems with potential applications in quantum technology and quantum simulation of condensed-matter problems [...

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Momentum-Space Josephson Effects

Cited by 31 publications

References 60 publications

Collective excitations and tunneling dynamics in long bosonic Josephson junctions

Collective excitations and tunneling dynamics in long bosonic Josephson junctions

Experimental realization of a long-lived striped Bose-Einstein condensate induced by momentum-space hopping

Many-body quantum dynamics of an asymmetric bosonic Josephson junction

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