Abstract
The excitation modes of two-dimensional liquid 4He are approached from two angles: Firstly, the phonon-roton spectrum is calculated and the related transition currents examined to gain insight into the detailed microscopic structure of the excitations and to look for possible evidence of the proposed spontaneous formation of vortex-antivortex pairs at low densities. The roton excitation is interpreted as a resonance effect in which the wavelength of the long-range density fluctuation matches favorably with the short-range oscillations caused by two-particle correlations. Contrary to the 3D case, no backflow rolls are observed in the two-body current at high momenta. The calculations reproduce reasonably the density dependence of the spectrum, and the saturation of the high-momentum part following from the decay processes of excitations is satisfactorily predicted. The stability of the liquid ground state is then studied by searching for soft modes. It is found that at densities near the expected liquid-solid phase transition the energy of the liquid can be lowered by changing the symmetry of the pair distribution function from spherical to non-spherical. This two-body structure indicates the point-group symmetry of the emerging solid phase to be hexagonal.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
REFERENCES
B. E. Clements et al., Phys. Rev. B 53, 12242 (1996).
.J. M. Kosterlitz and D. J. Thouless, J. Phys. C 6, 1181 (1973).
C. E. Campbell, R. Folk, and E. Krotscheclr. J. Low Temp. Phys. 105, 13 (1996).
S. Giorgini, J. Boronat, and J. Casulleras, Phys. Rev. B 54, 6099 (1996).
M. Saarela and F.V. Kusmartsev, Phys. Lett. A 202, 317 (1995).
P. A. Whitloclr, G. V. Chester, and M. H. Kalos, Phys. Rev. B 38, 2418 (1988).
M. C. Gordillo and D. M. Ceperley, Phys. Rev. B 58, 6447 (1998).
E. Krotscheck, Phys. Rev. B 31, 4258 (1985).
M. Saarela and J. Suominen, in Condensed Matter Theories, edited by J. Keller (Plenum, New York, 1989), Vol. 4, p. 377.
B. E. Clements et al., Phys. Rev. B 50, 6958 (1994).
V. Apaja and M. Saarela, Phys. Rev. B 57, 5358 (1998).
V. Apaja, J. Halinen, and M. Saarela, Physica B, in press.
V. Apaja, Ph.D. Thesis (University of Oulu, Oulu, 1999).
L. Castillejo et al., Phys. Rev. B 20, 3631 (1979).
A. D. Jackson et al., Phys. Rev. B 24, 105 (1981).
V. Apaja, J. Halinen, and M. Saarela, J. Low Temp. Phys. 113, 909 (1998).
R. E. Grisenti and L. Reatto, J. Low Temp. Phys. 109, 477 (1997).
V. Apaja et al., Phys. Rev. B 55, 12925 (1997).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Halinen, J., Apaja, V., Gernoth, K.A. et al. Excitations and Stability of 2D Liquid 4He. Journal of Low Temperature Physics 121, 531–536 (2000). https://doi.org/10.1023/A:1017542906483
Issue Date:
DOI: https://doi.org/10.1023/A:1017542906483