Microscopic theory of surface excitations in superfluid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>

Chang, C. C.; Cohen, Michael J.

doi:10.1103/physrevb.11.1059

Cited by 39 publications

(12 citation statements)

References 10 publications

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“…A good starting calculation for S(q ʈ ,) in the films is to use the Feynman theory of excitations 25 ͑generalized to the inhomogeneous geometry 26 ͒, where the elementary excitations are described by the ground state being modified by single density fluctuations. 22 Experience has shown that in spite of quantitative deficiencies, the qualitative features of the model are quite satisfactory.…”

Section: ͑22͒mentioning

confidence: 99%

Excitations in a thin liquidHe4film from inelastic neutron scattering

et al. 1996

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We perform a thorough analysis of the experimental dynamic structure function measured by inelastic neutron scattering for a low-temperature (Tϭ0.65 K͒ four-layer liquid 4 He film. The results are interpreted in light of recent theoretical calculations of the ͑nonvortex͒ excitations in thin liquid Bose films. The experimental system consists of four outer liquid layers, adsorbed to two solid inner 4 He layers, which are themselves adsorbed to a graphite substrate. Relatively intense surface ͑ripplon͒ and bulklike modes are observed. The analysis of the experimental data gives strong evidence for still other modes and supports the long-standing theoretical predictions of layerlike modes ͑layer phonons͒ associated with excitations propagating primarily within the liquid layers comprising the film. The results of the analysis are consistent with the occurrence of level crossings between modes, and the existence of a layer modes for which the theory predicts will propagate in the vicinity of the solid-liquid interface. The theory and experiment agree on the detailed nature of the ripplon; its dispersion at low momenta, its fall off in intensity at intermediate momenta, and the level crossings at high momentum. Similar to experiment, the theory yields an intense mode in the maxon-roton region which is intrepreted as the formation of the bulklike excitation.

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Section: ͑22͒mentioning

confidence: 99%

Excitations in a thin liquidHe4film from inelastic neutron scattering

et al. 1996

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“…Similarly, a negative temperature fluctuation will induce a continual decrease in temperature. The surface energy contribution of the zero-point motion of the phonon modes is readily obtained from (56) and (14). We find = ---+ 2F(x)-2 log tanh (60) 8zr where x = 2,rrTa/hc.…”

Section: Of Phonons Is Includedmentioning

confidence: 96%

“…The probability density is thus of the same form as before, with b 2 rcTr/hc d)~(r, T)-~ -r2 sinh (IrTr/hc) (56) and so the kinetic energy term --(h2/4m)V2~p in the total energy again has the form of a repulsive interaction. The screening length hc/~'T is approximately 5.8/~ at 1 K. Inserting (56) into (14) and considering contributions from particle separations greater than 2a, we find that the finite-temperature phonon zero-point motion contribution to the bulk energy is (when 27rTR/hc >> 1) 2 R 3 /2~rTa\ AEv=-~(hcno)~a F~--~c ) (57) where 1 x ( x cosh x~…”

Section: Of Phonons Is Includedmentioning

confidence: 99%

“…We find = ---+ 2F(x)-2 log tanh (60) 8zr where x = 2,rrTa/hc. The derivation of this expression is valid only when the total surface energy is greater than zero, since a spherical shape is assumed in (14). The low-temperature (2~-T << hc/a) expansion is…”

Section: Of Phonons Is Includedmentioning

confidence: 99%

“…Inserting (54) into(14), we find that the direct contribution of the infinite-range correlations arising out of the zero-point motion of the phonon fiat surface of area L 2, (54) similarly leads to a positive volume term and a -L z log (L/a) term. So at T = 0 the long-range part of the phonon correlations raises the bulk energy (i.e., from a variational point of view they should be left out to lower the total energy), and produces a negative R 2 log (R/a) term, as well as a negative R 2 term.…”

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confidence: 99%

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The surface of liquid 4He, based on the idea that ? i<j f(r ij) describes a droplet

Lekner

Henderson

1978

J Low Temp Phys

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We argue that the wave function 11 f(rij) describes the ground state of a droplet of liquid 4He. With this wave function, expressions for the surface energy e and the surface tension cr of liquid aBe at T = 0 are derived. Choosing particular f(r) and density profile, and the simplest pair correlation function, we plot the variation of e and cr with surface thickness t. For slow variation of density at the surface, e becomes proportional to t. The surface thickness is found to be about 4 ~. The inclusion of phonon zero-point motion correlations in the wave function leads (at T = O) to a-R 2 log R term in the energy of a droplet of radius R, implying a logarithmic divergence in both e and o'. At T > 0 the phonon correlations give a log T dependence of e and r and a negative bulk specific heat, Suggestions as to the reason for these problems are explored, but no definite conclusions are reached.

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