The effect of Aharanov-Bohm phase on the magnetic-field dependence of two-pulse echos in glasses at low temperatures

TL;DR

This paper investigates how the Aharanov-Bohm phase influences the magnetic-field dependence of two-pulse echoes in glasses at low temperatures, explaining several experimental features through an effective two-level system model.

Contribution

It introduces a model considering magnetic field effects via the Aharanov-Bohm phase on interacting two-level systems, explaining key experimental observations in glass echo experiments.

Findings

Explains dephasing at low magnetic fields

Describes dependence on electric field strength

Accounts for pulse separation and temperature effects

Abstract

The anomalous response of glasses in the echo amplitude experiment is explained in the presence of a magnetic field. We have considered the low energy excitations in terms of an effective two level system. The effective model is constructed on the flip-flop configuration of two interacting two level systems. The magnetic field affects the tunneling amplitude through the Aharanov-Bohm effect. The effective model has a lower scale of energy in addition to the new distribution of tunneling parameters which depend on the interaction. We are able to explain some features of echo amplitude versus a magnetic field, namely, the dephasing effect at low magnetic fields, dependence on the strength of the electric field, pulse separation effect and the influence of temperature. However this model fails to explain the isotope effects which essentially can be explained by the nuclear quadrupole moment. We will finally discuss the features of our results.