Crossing of Specific Heat Curves in some correlated Fermion systems

TL;DR

This paper explains the crossing of specific heat curves in correlated fermion systems as a consequence of proximity to a quantum critical point, highlighting a crossover from quantum to classical fluctuations near a characteristic temperature.

Contribution

It demonstrates that the crossing of specific heat curves is linked to quantum criticality and crossover phenomena, providing a theoretical framework within spin fluctuation theory.

Findings

Crossing points occur near the crossover temperature T^*.

Behavior is related to quantum critical points in fermion systems.

Crossing is explained by homogeneous functions of control parameters.

Abstract

Specific heat versus temperature curves for various pressures, or magnetic fields (or some other external control parameter) have been seen to cross at a point or in a very small range of temperatures in many correlated fermion systems. We show that this behavior is related to the vicinity of a quantum critical point in these systems which leads to a crossover at some temperature T^* from quantum to classical fluctuation regime. The temperature at which the curves cross turns out to be near T^*. We have discussed the case of the normal phase of liquid Helium three and the heavy fermion systems CeAl3 and UBe13 in detail within the spin fluctuation theory. When the crossover scale is any homogeneous function of these control parameters there is always crossing at a point.