Charge-Induced Instability of theHe4Solid-Superfluid Interface

The interface between crystalline and superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, when charged with negative ions, is deformed as a result of melting and crystallization processes. As long as the electric field normal to the interface is below a critical value, the deformation is stable and reversible. Above the critical field a charge-induced instability of the crystal is observed, which resembles the electrohydrodynamic instability of liquid surfaces.