Study of shock waves and solitons in bulk superfluid He4

Abstract

Properties of shock waves and solitons in superfluid 4 He were studied by time-resolved shadowgraph experiments and theoretical density functional theory calculations. Pressure estimates for shock waves and the bright soliton limit (0.2 MPa) were provided and compared with the semiclassical Rankine-Hugoniot theory. Overall, the shock wave amplitude-velocity relationship was observed to be linear at least up to 175 kg/m 3. At high amplitudes, the shock waves decay into sound waves in the wake as well as a bright soliton train in the front. This suggests that the experimental shadowgraph data in Phys. Rev. Lett. 120, 035302 (2018) corresponds to such a train structure rather than an individual bright soliton. With reference to theoretical calculations, a new approach based on accelerating wall embedded in the liquid is proposed for generating single solitons in superfluid helium. This process is also predicted to produce dark solitons in superfluid helium, which have not yet been observed experimentally. At low soliton amplitudes, collision with an exponentially repulsive wall results in nearly lossless reflection, which is accompanied by soliton inversion from dark to bright or bright to dark.

Merging of superfluid helium nanodroplets with vortices

“…Bright solitons in thin 4 He films adsorbed on solid substrates have been observed [38][39][40][41], and also in bulk superfluid 4 He [42,43]; so far, dark solitons have not been detected in superfluid 4 He. Instead, they have been observed in BECs [44][45][46][47][48].…”

Soliton–mean field interaction in Korteweg–de Vries dispersive hydrodynamics

“…Superfluids are another medium in which nonlinearity due to particle interactions and dispersion resulting from quantum matter wave interference lead to solitons and DSWs. [17][18][19][20] Solitons and DSWs have also been studied in stressed solids and magnetic materials. [21][22][23] The motivation for this focused review is the rapid and varied mathematical developments on this problem that have occurred within only a few years.…”

“…There has been significant interest in the propagation of large‐scale mean fields in spatial and fiber nonlinear optics, 13–16 where fundamental DSW properties have been favorably compared with Whitham modulation theory. Superfluids are another medium in which nonlinearity due to particle interactions and dispersion resulting from quantum matter wave interference lead to solitons and DSWs 17–20 . Solitons and DSWs have also been studied in stressed solids and magnetic materials 21–23 …”

Free surface lump wave dynamics of a saturated superfluid 4 He film with nontrivial boundary condition at the substrate surface

“…In an interesting recent work [16], the first experimental observation of bright soliton has been done in bulk superfluid 4 He. Some properties of shock waves in superfluid 4 He has been explored by time-resolved shadowgraph experiments in [17]. It has been shown that shock waves in superfluid helium evolve on a nanosecond time scale [18].…”