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Variational density-matrix theory of liquid /sup 4/He at nonzero temperatures

Journal Article · · Phys. Rev. B: Condens. Matter; (United States)
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We employ the minimum principle for the Helmholtz free energy to develop a self-consistent variational theory of liquid /sup 4/He at nonzero temperatures. Using the fact (demonstrated here) that the equilibrium density matrix of a boson system has non-negative matrix elements in coordinate representation, the trial density matrix in coordinate space is chosen to be an exponentiated sum of two-body functions. Adopting the separability assumption in conjunction with the hypernetted-chain approximation, we determine these functions optimally by a coupled set of Euler-Lagrange equations for the structure function S(k,T) and the energy epsilon(k,T) of the elementary excitations. In a phenomenological study we analyze the variation of S(k,T) and epsilon(k,T) with temperature, and discuss the relationship by employing experimental data on these functions at long wavelength and around the roton minimum.
Research Organization:
School of Physics and Astronomy, University of Minnesota, 116 Church Street S.E., Minneapolis, Minnesota 55455
OSTI ID:
6297984
Journal Information:
Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 30:7; ISSN PRBMD
Country of Publication:
United States
Language:
English

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Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BOSONS
DATA
DENSITY MATRIX
ENERGY
EQUILIBRIUM
EVEN-EVEN NUCLEI
FLUIDS
FORM FACTORS
FREE ENERGY
HELIUM 4
HELIUM ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
LIQUIDS
MATRICES
NUCLEI
NUMERICAL DATA
PARTICLE PROPERTIES
PHASE VELOCITY
PHYSICAL PROPERTIES
QUASI PARTICLES
ROTONS
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
THEORETICAL DATA
THERMODYNAMIC PROPERTIES
VARIATIONAL METHODS
VELOCITY