Surface Superconductivity in Topologically Nontrivial AuSn₄ using AC Magnetization

Chin-Wei Lin^1*, Hong-Zhang Liang¹, I-Nan Chen², Chia Nung Kuo³, Chin Shan Lue³, Li-Min Wang¹

¹Department of Physics/Graduate Institute of Applied Physics, National Taiwan University, Taipei, Taiwan
²Instrumentation Center, National Taiwan University, Taipei, Taiwan
³Department of Physics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Chin-Wei Lin, email:d05245001@ntu.edu.tw

Superconductors with nontrivial band topology are of significant interest due to their capacity to host quasiparticles such as Majorana fermions, which have potential applications in quantum computing. However, identifying bulk superconductors that combine intrinsic superconductivity with topological characteristics remains challenging. A primary difficulty lies in distinguishing topological surface states, as these are often obscured by dominant bulk superconductivity effects. In this study, we use AC magnetization to examine the superconducting properties of AuSn₄, an intermetallic compound with complex crystal symmetry and strong spin–orbit coupling, as a candidate for intrinsic topological superconductivity. Our AC magnetization measurements reveal an unusual diamagnetic response that persists beyond the bulk upper critical field H_c2, indicating possible surface superconductivity. This response extends close to the surface-critical field H_c3, suggesting a distinct transition associated with unique surface superconducting states. Our results demonstrate the effectiveness of AC magnetization techniques in probing topological superconductors and provide insights into the surface properties of bulk superconducting materials.

Keywords: Surface Superconductivity, Unconventional Superconductivity, AC Magnetization