Shock Waves in a Superfluid with Higher-Order Dispersion

Abstract

Higher-order dispersion can lead to intriguing dynamics that are becoming a focus of modern hydrodynamics research. Such systems occur naturally, for example in shallow water waves and nonlinear optics, for which several types of novel dispersive shocks structures have been identified. Here we introduce ultracold atoms as a tunable quantum simulations platform for higher-order systems. Degenerate quantum gases are well controlled model systems for the experimental study of dispersive hydrodynamics in superfluids and have been used to investigate phenomena such as vortices, solitons, dispersive shock waves and quantum turbulence. With the advent of Raman-induced spin-orbit coupling, the dispersion of a dilute gas Bose-Einstein condensate can be modified in a flexible way, allowing for detailed investigations of higher-order dispersion dynamics. Here we present a combined experimental and theoretical study of shock structures generated in such a system. The breaking of Galilean invariance by the spin-orbit coupling allows two different types of shock structures to emerge simultaneously in a single system. Numerical simulations suggest that the behavior of these shock structures is affected by interactions with vortices in a manner reminiscent of emerging viscous hydrodynamics due to an underlying quantum turbulence in the system. This result suggests that spin-orbit coupling can be used as a powerful means to tun the effective viscosity in cold-atom experiments serving as quantum simulators of turbulent hydrodynamics, with applications from condensed matter and optics to quantum simulations of neutron stars.dispersive shock waves ( s) that develop from non-linear interactions in the system [11]. A prototypical example of this is demonstrated in Fig. 1 showing the results of one-dimensional numerical simulations using realistic parameters to form the single component dispersion, shown in Fig. 6.Shock waves generated in a superfluid medium are typically

What is a quantum shock wave?

“…In the TG limit of infinitely strong interactions, where the phase coherence length is the same as the mean interparticle separation, the shock wave oscillations are absent for a sufficiently wide density bump (wider than the said mean interparticle separation). Apart from explaining the origin of density ripples in dispersive quantum shock waves, our results may serve as a test bed for new theoretical and computational techniques for many-body dynamics, such as the generalized hydrodynamics [51][52][53], and may shed new light in the understanding of dispersive shock waves in a variety of other contexts, such as in electronic systems described by the Calogero-Sutherland model and Korteweg-de Vries equations [1,8,54], or superfluids with higher-order dispersion [55]. K.V.K.…”

Quantum-torque-induced breaking of magnetic domain walls in ultracold gases

“…4), strongly suggest that these excitations are closely related to magnetic shock waves [22][23][24]. Shock waves have been studied in single component ultracold systems [25,26] and very recently, in the presence of spin-orbit coupling [27]. However, the LLE in the presence of both transverse magnetic field and anisotropy are not integrable and have been shown to present a chaotic behavior [28].…”