Dielectric susceptibility and heat capacity of ultra-cold glasses in magnetic fields

Abstract

Recent experiments demonstrated unexpected, even intriguing properties of certain glassy materials in magnetic field at low temperatures. We have studied the magnetic field dependence of the static dielectric susceptibility and the heat capacity of glasses at low temperatures. We present a theory in which we consider the coupling of the tunnelling motion to nuclear quadrupoles in order to evaluate the static dielectric susceptibility. In the limit of weak magnetic field we find the resonant part of the susceptibility increasing like B 2 while for the large magnetic field it behaves as 1/B. In the same manner we consider the coupling of the tunnelling motion to nuclear quadrupoles and angular momentum of tunnelling particles in order to find the heat capacity. Our results show the Schotky peak for the angular momentum part, and B 2 dependence for nuclear quadrupoles part of heat capacity, respectively. We discuss whether or not this approach can provide a suitable explanation for such magnetic properties.

Quadrupole effect on the heat conductivity of cold glasses

“…where these overlaps are dependent on the angle θ. (here θ is the angle between two axis of the Nuclear quadrupole in each wells 17 : e R 1 , e L 1 )…”

“…Several generalizations of the standard TLS model have been reported after the anomalous behavior of glasses in a magnetic field. According to these solutions, the models can be divided into "orbital" 10,11,12,13 and "spin" models (nuclear quadrupole effect) 14,15,16,17 . The "orbital" models can provide an explanation for some of the magnetic field effects by considering the flux dependence of the tunneling splitting.…”