Thermodynamic Instabilities in Quantum Liquids

Abstract

We propose a simple generalization of the criteria for thermodynamic stability that the Landau theory of Fermi liquids provides for zero temperatures. If the latter is nonvanishing, loss in the definition of the Fermi surface inhibits a well - established relationship between each thermodynamic response strength and one selected Landau parameter. We show that an extension of the Landau parameter to a temperature dependent field allows one to formulate the stability criteria in a similar fashion as in the zero temperature case. We discuss the application of these concepts to channels other than the spin symmetric - isospin symmetric one where the response to a scalar compression field takes place.