Investigating Sub-Coherence Length Confinement in Superfluid ³He using Nanofluidic Helmholtz Resonators

Superfluid ³He under strong confinement has attracted significant interest due to the observation of novel phases not present in the bulk [1, 2, 3]. Interactions with confining surfaces cause pair-breaking and significantly alter the free energy landscape of potential phases. We have studied the effects of confinement on superfluid phases of ³He using nanofluidic Helmholtz resonators, examining phase diagrams [3] and critical velocities in the A-phase [4]. The next generation of Helmholtz resonators are designed to provide sub-coherence length confinement in superfluid ³He [5], enabling us to probe phase transitions where traditional Ginzburg-Landau theory becomes inadequate. Additionally, we plan to use ⁴He preplating to modify the boundary conditions and study the effect of surface scattering [6]. Thus, we can investigate flow profiles and surface interactions under nanoscale confinement, offering new insights into hydrodynamics at the quantum level.

1. J.I.A. Li, A.M. Zimmerman, J. Pollanen, C.A. Collett and W.P. Halperin, Phys. Rev. Lett. 114, 105302 (2015).

2. L.V. Levitin, B. Yager, L. Sumner, B. Cowan, A.J. Casey, J. Saunders, N. Zhelev, R.G. Bennett and J.M. Parpia, Phys. Rev. Lett. 122, 085301 (2019).

3. A.J. Shook, V. Vadakkumbatt, P. Senarath Yapa, C. Doolin, R. Boyack, P.H. Kim, G.G. Popowich, F. Souris, H. Christani, J. Maciejko and J.P. Davis, Phys. Rev. Lett. 124, 015301 (2020).

4. A.J. Shook, E. Varga, I. Boettcher and J.P. Davis, Phys. Rev. Lett. 132, 156001 (2024).

5. E. Varga, C. Undershute and J.P. Davis, Phys. Rev. Lett. 129, 145301 (2022).

6. M.R. Freeman and R.C. Richardson, Phys. Rev. B 41, 11011 (1990).