Fermiology of a topological line-nodal compound CaSb2 and its implication to superconductivity: angle-resolved photoemission study

TL;DR

This study uses angle-resolved photoemission spectroscopy to explore the Fermi-surface topology of CaSb2, a topological line-nodal superconductor, revealing key features related to its superconductivity and potential for topological control.

Contribution

It provides the first detailed Fermi-surface mapping of CaSb2, highlighting the importance of a 3D hole pocket and the effects of sample doping on its topological and superconducting properties.

Findings

3D hole pocket at G point is common in samples.

Carrier doping level varies with fabrication conditions.

Presence of the electron pocket correlates with superconductivity.

Abstract

We performed angle-resolved photoemission spectroscopy with micro-focused beam on a topological line-nodal compound CaSb2 which undergoes a superconducting transition at the onset Tc~1.8 K, to clarify the Fermi-surface topology relevant to the occurrence of superconductivity. We found that a three-dimensional hole pocket at the G point is commonly seen for two types of single-crystalline samples fabricated by different growth conditions. On the other hand, the carrier-doping level estimated from the position of the chemical potential was found to be sensitive to the sample fabrication condition. The cylindrical electron pocket at the Y(C) point predicted by the calculations is absent in one of the two samples, despite the fact that both samples commonly show superconductivity with similar Ts's. This suggests a key role of the three-dimensional hole pocket to the occurrence of superconductivity, and further points to an intriguing possibility to control the topological nature of superconductivity by carrier tuning in CaSb2.