Third law of thermodynamics and the shape of the phase diagram for systems with a first-order quantum phase transition

摘要

The Third Law of Thermodynamics constrains the phase diagram of{systems witha first-order quantum phase transition. For zero conjugate field, thecoexistence curve has an infinite slope at T=0. If a tricritical point existsat T>0, then the associated tricritical wings are perpendicular to the T=0plane, but not to the zero-field plane. These results are based on the thirdlaw and basic thermodynamics only, and are completely general. As an explicitexample we consider the ferromagnetic quantum phase transition in clean metals,where a first-order quantum phase transition is commonly observed.