Anisotropic Interaction between Two-Level Systems

TL;DR

This paper calculates the anisotropic interaction between two-level systems in amorphous materials, revealing how their orientations and positions influence their interactions, with implications for understanding disordered solids.

Contribution

It extends previous models by explicitly analyzing the orientation dependence of TLS-TLS interactions and averaging over isotropic distributions.

Findings

Interaction depends on the angle between TLS orientation and connecting line

Derived a simplified expression for the averaged interaction

Analyzed the role of TLS orientation in amorphous materials

Abstract

Using the model of interaction between two-level systems (TLS) and strain fields introduced in Phys. Rev. B 75, 064202 (2007), we calculate the TLS-TLS interaction. We particularize our calculations to amorphous materials and analyze the dependence of the interaction Hamiltonian on the orientations of the two TLSs and of the direction that connects them. Assuming isotropic distribution of the TLSs orientations, we then averaged the interaction over one of the TLSs orientations. The resulting interaction depends in a simple way on the angle between the orientation of the other TLS and the line that connects the two TLSs.