Near-surface Superconductivity in Topological GaSb and Bi2Se3 Whiskers

Near-surface superconductivity in topologically interesting semiconductor whiskers such as GaSb and Bi2Se3 remains an important topic for understanding unconventional pairing mechanisms and the interplay of quantum effects at the nanoscale. Bi2Se3 occupies a special place among topological materials due to its strong spin-orbit interaction and robust surface states, which create conditions for realizing topological superconductivity capable of supporting Majorana fermions and novel quantum phases. Inducing superconductivity through controlled doping or self-organized heterointerfaces provides a practical pathway without the need for extreme pressures or complex epitaxial layering, although operation still requires cryogenic temperatures typical for low-Tc superconductors. GaSb whiskers doped with tellurium and Bi2Se3 whiskers doped with palladium were synthesized by chemical vapor deposition and examined at cryogenic temperatures down to 1.5 K under magnetic fields up to 14 T. Resistance measurements revealed a sharp drop below 4.2 K in GaSb and below 5.3 K in Bi2Se3, indicating partial superconducting transitions likely confined to the near-surface regions. The upper critical magnetic field Bc(T) derived from magnetorsistance data fits the Ginzburg–Landau model, yielding coherence lengths of about 1.7 nm for GaSb and 15 nm for Bi2Se3, values comparable to or smaller than those found in high-Tc superconductors, pointing to nontrivial pairing behavior or enhanced spin-orbit-driven mechanisms. Shubnikov-de Haas oscillations observed in GaSb whiskers confirm high crystalline quality and exclude amorphization as the origin of the effect. A transition from weak antilocalization to localization and clear signatures of the Kondo interaction indicate a competition between superconducting pairing and quantum scattering processes. In doped GaSb whiskers near the MIT, partial localization of carriers and their interaction with free electrons leads to suppression of Cooper pairing at elevated temperatures. This coexistence of partial superconductivity, weak localization, and Kondo behavior demonstrates the complex balance of competing electronic correlations in these low-dimensional systems. Such findings expand the understanding of surface-limited superconductivity in topological and A3B5 semiconductor whiskers and provide a foundation for engineering heterostructures capable of hosting exotic superconducting phases useful for quantum devices.