Negative Differential Conductivity in an Interacting Quantum Gas

Labouvie, Ralf; Santra, B.; Heun, Simon; Wimberger, Sandro; Ott, Herwig

doi:10.1103/physrevlett.115.050601

Cited by 119 publications

(177 citation statements)

References 38 publications

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“…quadratically with J, which is characteristic for an incoherent transport process [19]. In the presence of dissipation we find that below a critical dissipation rate γ RB , the lattice site refills completely, reaching again a superfluid steady-state as discussed above (Fig.…”

Section: Fig 3 (A)mentioning

confidence: 60%

“…To visualize this effect we show in Fig. 2(c) the current-voltage characteristic for the steady-states, converting atom number difference in chemical potential difference [19]. The graph displays the well-known behaviour of a superconductor, where a supercurrent is present for vanishing voltage.…”

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confidence: 99%

“…Steady-states have the peculiar property that they can be attractor states of the phase space dynamics. Controlling an open quantum system can therefore be a robust way to prepare well-designed quantum states.In the experiment, we study a weakly-interacting, superfluid Bose-Einstein condensate of rubidium atoms in a one-dimensional periodic potential with high occupancy per site [17,19]. Each site contains a small condensate (N 0 ≈ 700 atoms in the center of the trap) and all of them are connected via the tunneling coupling J, which is controlled by the height of the optical lattice.…”

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confidence: 99%

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Bistability in a Driven-Dissipative Superfluid

et al. 2016

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We experimentally study a driven-dissipative Josephson junction array, realized with a weakly interacting Bose Einstein condensate residing in a one-dimensional optical lattice. Engineered losses on one site act as a local dissipative process, while tunneling from the neighboring sites constitutes the driving force. We characterize the emerging steady-states of this atomtronic device. With increasing dissipation strength γ the system crosses from a superfluid state, characterized by a coherent Josephson current into the lossy site to a resistive state, characterized by an incoherent hopping transport. For intermediate values of γ, the system exhibits bistability, where a superfluid and a resistive branch coexist. We also study the relaxation dynamics towards the steady-state, where we find a critical slowing down, indicating the presence of a non-equilibrium phase transition.PACS numbers: 03.75. Lm, 74.40.Gh, 03.65.Yz, 42.50.Dv Non-equilibrium steady-states constitute fix points of the phase space dynamics of classical and quantum systems [1][2][3]. They emerge under the presence of a driving force and lie at the heart of transport phenomena such as heat conduction [4][5][6] or current flow [7][8][9]. They also naturally appear in open quantum systems [10,11] and are connected to the study of non-equilibrium thermodynamics and non-equilibrium quantum phase transitions [12]. It has been pointed out that engineering open quantum systems can induce a phase space dynamics which drives the quantum system in a pure state by solely dissipative means [13][14][15][16]. Controlling and understanding the non-equilibrium steady-states of an open many-body quantum system therefore offers new routes for quantum state engineering and out-of-equilibrium quantum dynamics. Here, we investigate the steady-states of a driven-dissipative Josephson junction array realized with a Bose-Einstein condensate in a one-dimensional optical lattice [17]. Varying the strength of the dissipation, the system can be tuned from superfluid to resistive transport. In between, it exhibits a region of bistability. The peculiar transport properties make such devices promising elements for complex atomtronic circuits. At the same time, they are an interesting candidate to study generic properties of an open quantum system. Our results manifest the high potential of open system control in ultracold quantum gases.Open quantum systems are characterized by the competition between the intrinsic unitary dynamics, governed by the Hamilton operator H, and the coupling to the environment, which induces non-unitary time evolution and quantum jumps, described by jump operators (â i ,â i † ) which act on the system with rates γ i [10]. The time evolution of the density matrix ρ in Markov approximation is then described by a master equation in Lindblad form [18]:FIG. 1. Schematics of the experiment. One site of an array of superfluids is subject to an incoherent local loss process with rate γ. The coherent tunneling coupling between the reservoir sites is given b...

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confidence: 60%

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Bistability in a Driven-Dissipative Superfluid

et al. 2016

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“…Additional features at higher filling At or above n F = 1/2 or n B = 1, strong interactions lead to additional phenomena. For example, negative differential conductance (NDC), where the current decreases as the driving force increases, has been discussed in fermions [32] and observed in bosons [57]. In isolated systems, energy conservation can lead to dynamically insulating phases [32,58].…”

Section: (B) and (D)mentioning

confidence: 99%

Quantification of the memory effect of steady-state currents from interaction-induced transport in quantum systems

Lai

Chien

2017

Phys. Rev. A

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Dynamics of a system in general depends on its initial state and how the system is driven, but in many-body systems the memory is usually averaged out during evolution. Here, interacting quantum systems without external relaxations are shown to retain long-time memory effects in steady states. To identify memory effects, we first show quasi-steady state currents form in finite, isolated Bose and Fermi Hubbard models driven by interaction imbalance and they become steady-state currents in the thermodynamic limit. By comparing the steady state currents from different initial states or ramping rates of the imbalance, long-time memory effects can be quantified. While the memory effects of initial states are more ubiquitous, the memory effects of switching protocols are mostly visible in interaction-induced transport in lattices. Our simulations suggest the systems enter a regime governed by a generalized Fick's law and memory effects lead to initial-state dependent diffusion coefficients. We also identify conditions for enhancing memory effects and discuss possible experimental implications.

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“…Besides the clear gravitational analogue, the study of such quasi-stationary scenarios is of general interest for the investigation of atom quantum transport [30][31][32][33][34][35][36][37], within the emergent field of atomtronics [38,39]. For instance, the considered setup can be used to provide a quasi-stationary supersonic current, with a well controlled atom velocity.…”

Section: Introductionmentioning

confidence: 99%

Quantum Transport in the Black‐Hole Configuration of an Atom Condensate Outcoupled Through an Optical Lattice

2017

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The outcoupling of a Bose-Einstein condensate through an optical lattice provides an interesting scenario to study quantum transport phenomena or the analog Hawking effect as the system can reach a quasi-stationary black-hole configuration. We devote this work to characterize the quantum transport properties of quasi-particles on top of this black-hole configuration by computing the corresponding scattering matrix. We find that most of the features can be understood in terms of the usual Schrödinger scattering. In particular, a transmission band appears in the spectrum, with the normal-normal transmission dominating over the anomalous-normal one. We show that this picture still holds in a realistic experimental situation where the actual Gaussian envelope of the optical lattice is considered. A peaked resonant structure is displayed near the upper end of the transmission band, which suggests that the proposed setup is a good candidate to provide a clear signal of spontaneous Hawking radiation.

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Negative Differential Conductivity in an Interacting Quantum Gas

Cited by 119 publications

References 38 publications

Bistability in a Driven-Dissipative Superfluid

Bistability in a Driven-Dissipative Superfluid

Quantification of the memory effect of steady-state currents from interaction-induced transport in quantum systems

Quantum Transport in the Black‐Hole Configuration of an Atom Condensate Outcoupled Through an Optical Lattice

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