Contact resistance and phase slips in mesoscopic superfluid-atom transport

S. Eckel, Jeffrey G. Lee, F. Jendrzejewski, C. J. Lobb, G. K. Campbell, and W. T. Hill, III

Phys. Rev. A 93, 063619 – Published 15 June 2016

Abstract

We experimentally measure transport of superfluid, bosonic atoms in a mesoscopic system: a small channel connecting two large reservoirs. Starting far from equilibrium (superfluid in a single reservoir), we observe first resistive flow transitioning at a critical current into superflow, characterized by oscillations. We reproduce this full evolution with a simple electronic circuit model. We compare our fitted conductance to two different microscopic phenomenological models. We also show that the oscillations are consistent with LC oscillations as estimated by the kinetic inductance and effective capacitance in our system. Our experiment provides an attractive platform to begin to probe the mesoscopic transport properties of a dilute, superfluid, Bose gas.

Received 26 October 2015

DOI:https://doi.org/10.1103/PhysRevA.93.063619

Physics Subject Headings (PhySH)

Bosons Superfluidity Transport phenomena

Atomic, Molecular & Optical

Authors & Affiliations

S. Eckel, Jeffrey G. Lee, F. Jendrzejewski, C. J. Lobb, G. K. Campbell, and W. T. Hill, III^*

Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899, USA

^*wth@umd.edu

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 93, Iss. 6 — June 2016

Reuse & Permissions

Access Options

Article Available via CHORUS

Download Accepted Manuscript

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
In situ images of a BEC of $495 (16) \times 10^{3} {}^{23}{Na}$ atoms in the dumbbell-shaped potential for trapping parameters that yield an equilibrium 1D density of atoms in the channel of 790(25) $μ m^{- 1}$ . Atoms are initially trapped in the left reservoir. At time $t = 0$ ms, a gate is removed, and the atoms are allowed to flow freely between the reservoirs.
Reuse & Permissions
Figure 2
(a) Example 10-ms time-of-flight (TOF) images of the condensate after the atom number imbalance has reached equilibrium (612 ms after opening the gate). In almost all TOF images, we observe vortices, primarily in the initially empty reservoir, showing evidence of the Feynman mechanism for vortex production [32]. (b) In the Feynman model, superfluid flows out of a channel into a reservoir. When the flow rate exceeds a critical value, vortex-antivortex pairs are created.
Reuse & Permissions
Figure 3
Normalized atom number imbalance between the two reservoirs vs time, for a total atom number of $472 (22) \times 10^{3}$ . The three plots shown are for different one-dimensional densities of atoms in the channel $n_{1D}$ : red circles, 790(25) $μ m^{- 1}$ ; green triangles, 665(16) $μ m^{- 1}$ ; and blue inverted triangles, 599(17) $μ m^{- 1}$ . For clarity, decay measurements are artificially offset vertically by 0.5. Solid curves are fits to the expected dynamics from the circuit shown in the inset (see text).
Reuse & Permissions
Figure 4
Calculated reservoir chemical potential $μ$ (green points) vs atom number $N$ . The magenta line shows the best-fit power law. Inset: Measured power required in the gate beam to trap all the atoms in the source with the Thomas-Fermi calculated chemical potential $μ$ . The dashed red line shows a linear fit and confirms the expected scaling.
Reuse & Permissions
Figure 5
Measured conductance $G$ vs (a) the one-dimensional density of atoms in the channel, $n_{1D}$ , and (b) the height of the optical potential, $U_{m}$ . The solid black line is a linear fit, and the colored curves are the fits to the Feynman conductance (see text). Experimental data are grouped by total atom number: violet squares, $472 (22) \times 10^{3}$ ; cyan inverted triangle, $331 (11) \times 10^{3}$ ; green triangles, $229 (9) \times 10^{3}$ ; red circles, $125 (6) \times 10^{3}$ . Violet squares correspond to the data shown in Fig. 3.
Reuse & Permissions
Figure 6
Comparison between experimentally observed and theoretical values for both (a) the period of LC oscillation and (b) the critical velocity for vortex production in the system. In both plots, the data points are the values for each decay measurement (run), and the solid line is the weighted mean of these values, with the standard deviation represented by the shaded region. Experimental data are grouped by total atom number and delineated by color and symbol as in Fig. 5.
Reuse & Permissions

Physical Review A

covering atomic, molecular, and optical physics and quantum information