Hysteresis in a quantized superfluid ‘atomtronic’ circuit

Abstract

is an emerging interdisciplinary field that seeks new functionality by creating devices and circuits where ultra-cold atoms, often superfluids, play a role analogous to the electrons in electronics. Hysteresis is widely used in electronic circuits, e.g., it is routinely observed in superconducting circuits 3 and is essential in rf-superconducting quantum interference devices [SQUIDs] 4 . Furthermore, hysteresis is as fundamental to superfluidity 5 (and superconductivity) as quantized persistent currents [6][7][8] , critical velocity [9][10][11][12][13][14] , and Josephson effects 15,16 . Nevertheless, in spite of multiple theoretical predictions 5,[17][18][19] , hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate (BEC).Here we demonstrate hysteresis in a quantized atomtronic circuit: a ring of superfluid BEC obstructed by a rotating weak link. We directly detect hysteresis between quantized circulation states, in contrast to superfluid liquid helium experiments that observed hysteresis directly in systems where the quantization of flow could not be observed 20 and indirectly in systems that showed quantized flow 21,22 . Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The 1 arXiv:1402.2958v2 [cond-mat.quant-gas]

Probing the circulation of ring-shaped Bose-Einstein condensates

“…Thus it follows that we should be able to rely on the TDGPE to also be a reliable predictor of the dynamics of the condensate cloud after release. This conclusion may be contrasted with recent work [17][18][19], [20] which indicates that some of the dynamics of the in-situ cloud (e.g., phase-slippage due to vortex dynamics) may not be as well predicted by zero-temperature mean-field theory.…”

Conical refraction: fundamentals and applications

“…The numerical simulations agree well with the experimental results on the dynamics of a trapped 87 Rb BEC in the PDR of CR. In addition to the advantages commented above in terms of power efficiency and beam quality, the minimum (and practically null) intensity circle offered by the toroidal dark trap avoids photon scattering and presents no corrugation of the potential minimum at the focal plan, at variance with techniques based on LG beams [209] or amplitude masks [210][211][212]. A range of applications of this technique can be envisioned: for optimized beam geometries, i.e., small w 0 , R 0 , and z R , the toroidal dark focus of the PDR generated by CR could be used to built an all-optical trap for BECs using a single beam.…”

“…For ultra-cold atoms, dark ORPs have the advantage of substantially reducing atom heating and decoherence rates [198] because of the low rate of spontaneous photon scattering as well as producing intrinsically flat potential minima. Blue-detuned ORPs have been experimentally reported by means of LG beams generated with spatial light modulators (SLMs) [209] and by amplitude masks [210][211][212]. These two techniques might experience the following limitations: (i) a significant fraction of the input power is lost and, therefore, it does not contribute to create the optical trap, (ii) the smoothness and, therefore, the quality of the trapping potential is limited by the size and number of pixels for the SLMs and the resolution of the printing system for the amplitude masks, and (iii) an accurate control on the position and alignment of the optical elements being used is required.…”

Dimensional reduction in Bose-Einstein condensed clouds of atoms confined in tight potentials of any geometry and any interaction strength

“…Soon after solitary waves were observed in an elongated trap [2] and in a more oblate one [3]. More recently toroidal and annular traps have been built, and even persistent currents have been observed, see, e.g., [4][5][6][7][8][9][10][11][12]. Remarkably, it has also become possible to manipulate the shape of the trapping potentials to a very high degree, see, e.g., Ref.…”