Dynamical Consequences of Time-Reversal Symmetry for Systems with Odd Number of Electrons: Conical Intersections, Semiclassical Dynamics, and Topology

TL;DR

This paper explores how time-reversal symmetry and electron count affect conical intersections, revealing topological invariants and providing exact semiclassical solutions that demonstrate topologically protected wavepacket features.

Contribution

It identifies topological invariants associated with conical intersections in systems with different electron counts and time-reversal symmetry, and derives exact semiclassical solutions.

Findings

Topological invariants differ between even and odd electron systems.

Exact semiclassical solutions reveal topologically protected wavepacket features.

Wavepacket structures serve as robust evidence of passing through conical intersections.

Abstract

In this manuscript we identify the main differences between the effects of Kramers symmetry on the systems with even and odd number of electrons, the ways how the aforementioned symmetry affects the structure of the Conical Seams (CSs), and how it shows up in semiclassical propagation of nuclear wavepackets, crossing the CSs. We identify the topological invariants, associated with CSs, in three cases: even and odd number of electrons with time-reversal symmetry, as well as absence of the latter. We obtain asymptotically exact semiclassical analytical solutions for wavepackets scattered on a CS for all three cases, identify topological features in a non-trivial shape of the scattered wavepacket, and connect them to the topological invariants, associated with CSs. We argue that, due to robustness of topology, the non-trivial wavepacket structure is a topologically protected evidence of a wavepacket having passed through a CS, rather than a feature of a semiclassical approximation.