Unambiguous detection of topological nodes via Berry monopole indicators

TL;DR

This paper introduces a novel method to detect topological band crossing nodes unambiguously by measuring the response current to a textured external field, avoiding reliance on edge mode detection.

Contribution

The work proposes a Berry monopole indicator based on bulk response currents, offering a new approach for unambiguous detection of topological nodes without edge mode analysis.

Findings

Berry monopole indicator w effectively signals proximity to topological nodes.

Response current J mirrors the texture of external field A near the nodal point.

Method provides a new bulk-based perspective for topological node detection.

Abstract

The unambiguous detection of the band topology for topological nodal systems remains an urgent problem in this field. Usually in experiments this relies on the detection for the topological edge modes, which may requires the high demands for the preparation and purifications of the materials and may give ambiguities. In this work, we propose a new approach towards the unambiguous detection of the bulk band crossing nodes of topological nodal systems without evolving the edge mode. The spirit of our proposal is to couple our targeted Hamiltonian to an weak external field $\mathbf {A}$ with a spatial varying texture in a compact manifold which may lead to the variation of the wavevector $\mathbf {k}$, and the system will have a response current $\mathbf {J}$. When the field $\mathbf {A}$ is close to the nodal point, the current $\mathbf {J}$ has the same texture as $\mathbf {A}$, indicating that we may turn the measurement for the bulk topological band crossing nodes into the measurement for the spatial texture of $\mathbf {J}$, and a Berry monopole indicator indicator $w$ can be constructed to indicate the distance between the field $\mathbf {A}$ and the band crossing node. Our findings provide an new perspective for the detection of band topology and pave the way for the further theoretical and experimental studies.