Topological characteristics of gap closing points in nonlinear Weyl semimetals

TL;DR

This paper investigates how onsite nonlinearity affects three-dimensional Weyl semimetals, revealing that Weyl nodes can transform into nodal lines and surfaces, with proposed methods to detect these topological changes.

Contribution

It introduces the novel finding that nonlinearity causes Weyl nodes to break into nodal structures while maintaining topological charge, and proposes experimental detection methods.

Findings

Weyl nodes break into nodal lines and surfaces at different energies due to nonlinearity.

Additional nodal lines can emerge at high nonlinearity levels.

Adiabatic pumping and Aharonov-Bohm interference are effective detection methods.

Abstract

In this work we explore the effects of nonlinearity on three-dimensional topological phases. Of particular interest are the so-called Weyl semimetals, known for their Weyl nodes, i.e., point-like topological charges which always exist in pairs and demonstrate remarkable robustness against general perturbations. It is found that the presence of onsite nonlinearity causes each of these Weyl nodes to break down into nodal lines and nodal surfaces at two different energies while preserving its topological charge. Depending on the system considered, additional nodal lines may further emerge at high nonlinearity strength. We propose two different ways to probe the observed nodal structures. First, the use of an adiabatic pumping process allows the detection of the nodal lines and surfaces arising from the original Weyl nodes. Second, an Aharonov-Bohm interference experiment is particularly fruitful to capture additional nodal lines that emerge at high nonlinearity.