Superconductivity and a van Hove singularity confined to the surface of a topological semimetal.
basic_science · Level V
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- Record sourced from PubMed, PMID 40301307.
- Also identified by DOI 10.1038/s41467-025-58024-w and PMC identifier 12041569.
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Abstract
The interplay between topology and superconductivity generated great interest in condensed matter physics. Here, we unveil an unconventional two-dimensional superconducting state in the Dirac nodal line semimetal ZrAs<sub>2</sub> which is exclusively confined to the top and bottom surfaces within the crystal's ab plane. As a remarkable consequence, we present the first clear evidence of a Berezinskii-Kosterlitz-Thouless (BKT) transition occurring solely on a material's surface-specifically, ZrAs₂-unlike the inconsistent reports on PtBi₂, CaAgP, and CaAg₁₋ₓPdₓP. Furthermore, we find that these same surfaces also host a two-dimensional van Hove singularity near the Fermi energy. This leads to enhanced electronic correlations that contribute to the stabilization of superconductivity at the surface of ZrAs<sub>2</sub>. The`surface-confined nature of the van Hove singularity and associated superconductivity, realized for the first time, allows exploring the interplay between low-dimensional quantum topology and superconductivity in a bulk material without resorting to the superconducting proximity effect.