Time reversal of pseudo-spin 1/2 degrees of freedom

TL;DR

This paper classifies pseudo-spin 1/2 systems based on their behavior under time reversal, revealing two types with distinct symmetry properties and discussing observable consequences for experimental identification.

Contribution

It introduces a new classification of pseudo-spin 1/2 degrees of freedom based on their time reversal properties, expanding understanding of spin-like systems.

Findings

Two types of pseudo-spin 1/2 distinguished by time reversal behavior

Observable differences between the two pseudo-spin types

Physical examples illustrating the second type's unique properties

Abstract

We show that pseudo-spin 1/2 degrees of freedom can be categorized in two types according to their behavior under time reversal. One type exhibits the properties of ordinary spin whose three Cartesian components are all odd under time reversal. For the second type, only one of the components is odd while the other two are even. We discuss several physical examples for this second type of pseudo-spin and highlight observable consequences that can be used to distinguish it from ordinary spin.