Contemporary Insights into Electronic Structure and Microscopic Transport in Nodal-Line Semimetals

TL;DR

This review comprehensively discusses the theoretical and experimental aspects of nodal-line semimetals, emphasizing symmetry protection, topological features, and their unique electronic and transport properties.

Contribution

It provides a unified overview of the classification, symmetry considerations, experimental signatures, and potential applications of nodal-line semimetals, highlighting recent advances.

Findings

Nodal-line semimetals exhibit characteristic surface states called drumhead bands.

Symmetry breaking can induce transitions from nodal-line to other topological phases.

Angle-resolved photoemission spectroscopy effectively probes the electronic structure of these materials.

Abstract

Topological semimetals have emerged as an important class of quantum materials with novel electronic responses and unconventional transport phenomena. Among them, nodal-line semimetals are distinguished by band crossings that extend along one-dimensional lines in momentum space rather than occurring at discrete points, forming closed loops, chains, or extended lines. The stability of these nodal structures is governed by crystalline symmetries such as mirror, spin-rotation, and nonsymmorphic operations, which give rise to characteristic topological invariants and surface states, including drumhead-like bands. In this review, we present a comprehensive overview of the theoretical framework and experimental realization of nodal-line semimetals, with particular emphasis on symmetry protection and the consequences of symmetry breaking. We discuss the classification of nodal-line structures, their evolution into other topological phases, and their signatures in electronic structure measurements and transport phenomena. Special attention is given to insights obtained from angle-resolved photoemission spectroscopy and related probes. By bringing together symmetry analysis, band topology, and experimental observations, this review aims to clarify the relationship between topology, magnetism, and measurable electronic responses in nodal-line semimetals. These considerations highlight their potential as a versatile platform for next-generation topological electronic functionalities and emergent quantum phenomena beyond conventional paradigms.