Equilibrium shape of 4He crystals near critical surface directions
L.A. Melnikovskya,b aKapitza Institute of Physical Problems, Russian Academy of Sciences, ul. Kosygina 2, Moscow, 117334, Russian Federation bNational Research University Higher School of Economics, ul. Myasnitskaya 20, Moscow, 101000, Russian Federation
Conditions for applicability of mean field theory to the thermodynamics of the 4He crystal surface are determined. Although the faceting transition itself is of Berezinsky—Kosterlitz—Thouless type, the thermodynamic potential outside a narrow neighborhood of the transition temperature can be expanded in the spirit of the Landau theory of second-order phase transitions. The Ginzburg—Levanyuk parameter is estimated. The singular behavior of the surface stiffness near critical directions observed for essentially non-critical temperatures is explained.
Keywords: quantum crystals, phase transitions, surface phenomena, Berezinsky—Kosterlitz—Thouless transitions PACS:05.70.Np, 67.80.−s, 68.35.−p, 68.35.Rh (all) DOI:10.3367/UFNe.2017.12.038352 URL: https://ufn.ru/en/articles/2018/11/g/ Citation: Andreev A F, Melnikovsky L A "Equilibrium shape of 4He crystals near critical surface directions" Phys. Usp.61 1090–1093 (2018)