Anisotropic Superconductivity under an in-plane magnetic field using Corbino electrodes and its implication: From Fe (Te, Se)/Bi₂Te_3 to Fe (Te, Se)/SrTiO₃

Emergent physical phenomena like superconductivity are highly promising for advancements in quantum computing and sensing. Among these, topological superconductivity stands out as a revolutionary solution, as it addresses the long-standing challenge of achieving fault-tolerant quantum computing through the realization of robust and resilient qubits. Symmetry breaking in physics often signals remarkable phenomena. In superconductors, rotational symmetry breaking gives rise to nematic superconductivity, theoretically linked to unconventional Cooper pair pairing. Electrical transport experiments are commonly used to probe rotational symmetry breaking, with Corbino geometry being a widely used tool due to its symmetric device design, enabling azimuthally isotropic electron flow and eliminating geometric artifacts. In this work, using epitaxially grown Fe(Te, Se)/Bi₂Te₃ thin films, we observe mild six-fold oscillations superposed on dominant two-fold oscillations in the superconducting vortex state. We attribute the two-fold oscillations, surprisingly, to a failure of Corbino geometry in providing truly isotropic electron flow, as confirmed in a polycrystalline s-wave superconductor, MoRe, under similar conditions. By isolating the two-fold background, we uncover intrinsic six-fold oscillations, which we propose originate from interfacial superconductivity contributed by the underlying topological layer, Bi₂Te₃. These findings challenge conventional assumptions about Corbino geometry and highlight the interplay between topology and superconductivity. Ongoing experiments aim to unravel the precise origins of these intrinsic observations.