Experimental realization of two-dimensional Dirac nodal line fermions in monolayer Cu<sub>2</sub>Si.
basic_science · Level V
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- Record sourced from PubMed, PMID 29044100.
- Also identified by DOI 10.1038/s41467-017-01108-z and PMC identifier 5647340.
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Abstract
Topological nodal line semimetals, a novel quantum state of materials, possess topologically nontrivial valence and conduction bands that touch at a line near the Fermi level. The exotic band structure can lead to various novel properties, such as long-range Coulomb interaction and flat Landau levels. Recently, topological nodal lines have been observed in several bulk materials, such as PtSn<sub>4</sub>, ZrSiS, TlTaSe<sub>2</sub> and PbTaSe<sub>2</sub>. However, in two-dimensional materials, experimental research on nodal line fermions is still lacking. Here, we report the discovery of two-dimensional Dirac nodal line fermions in monolayer Cu<sub>2</sub>Si based on combined theoretical calculations and angle-resolved photoemission spectroscopy measurements. The Dirac nodal lines in Cu<sub>2</sub>Si form two concentric loops centred around the Γ point and are protected by mirror reflection symmetry. Our results establish Cu<sub>2</sub>Si as a platform to study the novel physical properties in two-dimensional Dirac materials and provide opportunities to realize high-speed low-dissipation devices.