How IFIMAC Visualized Vortices in a Topological Superconductor

Researchers have directly observed quantized superconducting vortices within the two-dimensional material γ-PtBi₂, confirming the existence of macroscopic quantum phase coherence in what is described as a putative topological superconductor. Recent findings suggested surface superconductivity with a critical temperature of 2.9 K and a critical field of 1.8 T, values orders of magnitude larger than the bulk value, but evidence of these fundamental quantum features had remained elusive. Using low-temperature Scanning Tunneling Microscopy, the team linked these vortices to Fermi arcs present on the surface of γ-PtBi₂, and also demonstrated the Josephson effect. This observation addresses questions about the robustness of phase coherence and suggests a connection between the surface states of this topological semimetal and the emergence of the superconducting phase.

The layered compound γ-PtBi₂ exhibits superconductivity at 2.9 K with a critical field of 1.8 Tesla, a finding that addresses previous concerns regarding phase coherence within the material. These observations are significant given γ-PtBi₂’s classification as a topological semimetal, possessing Fermi arcs at its surface that connect bulk Weyl points. The team’s work extends beyond vortex identification; demonstration of the Josephson effect further solidifies the superconducting state. The researchers report observing quantized superconducting vortices and the Josephson effect, demonstrating a coherent quantum state. This detailed analysis, achieved through low-temperature STM, offers a new understanding of superconductivity in topological semimetals and their potential for quantum technologies.

Confirming superconductivity in layered materials like γ-PtBi₂ has been complicated by questions surrounding the maintenance of phase coherence. While previous studies indicated a critical temperature significantly higher than the bulk value, direct observation of key superconducting phenomena remained elusive. The demonstration of the Josephson effect alongside vortex identification solidifies the understanding of γ-PtBi₂ as a two-dimensional superconductor, offering new insights into the behavior of these materials and potentially enabling novel quantum devices.