Theory of Temperature Dependence of Elementary Excitation Energy
Assuming that the total Hamiltonian of liquid helium is completely diagonalized by a unitary operator, we can introduce “dressed-boson” operators as the unitary transformation of creation and annihilation operators of a helium atom. Then we can make a new viewpoint for the elementary excitation of liquid helium on the basis of the concept of the “dressed-boson”. The temperature dependence of the elementary excitation energy is studied. It is verified that the elementary excitation with a small momentum softens as the temperature approaches λ-point. The detection of the softening is proposed.
KeywordsLiquid Helium Thermodynamic Limit Unitary Transformation Annihilation Operator Helium Atom
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