Spin Response of a Magnetic Monopole and Quantum Hall Response in Topological Lattice Models through Local Invariants and Light

TL;DR

This paper develops a geometrical framework connecting magnetic monopoles, quantum Hall effects, and topological lattice models, revealing how local invariants and light responses characterize topological phase transitions.

Contribution

It introduces an effective magnetic moment for monopoles, relates it to quantum Hall currents, and links local invariants with topological phase transitions in lattice models.

Findings

Magnetic susceptibility quantized within topological phases

Relation between local invariants and quantum Hall response

Numerical analysis of topological invariants in lattice models

Abstract

Here, we elaborate on and develop the geometrical approach introduced in K. Le Hur, Physics Reports 1104 1-42 (2025) between the magnetic monopole created from a radial field, quantum physics and topological lattice models through quantum phase transitions. We introduce an effective magnetic moment for a monopole when applying an additional source field along z-direction which also mediates the quantum phase transition. We present its relation with the transverse pumped quantum Hall current. The magnetic susceptibility can be introduced as a measure of the topological invariant i.e. it remains quantized within the topological phase until the transition. We show the relation with two-dimensional topological lattice models such as a honeycomb Haldane model in real space. We develop the theory and present a numerical analysis between local invariants in momentum space introduced from Dirac points, correlation functions and the responses to circularly polarized light. We develop the formalism for coupled-planes materials including the possibility of quantum spin Hall effect and address a relation between the Ramanujan infinite alternating series and an interface in real space with a topological number one-half.