Magnetic field decouples nodeless surface and nodal bulk orders in PdTe

TL;DR

This study uses magnetic-field-dependent spectroscopy to distinguish and analyze the surface and bulk superconducting states in PdTe, revealing how magnetic fields can decouple these states due to their different gap structures.

Contribution

It provides the first spectroscopic evidence of magnetic field-induced decoupling of surface and bulk superconducting orders in PdTe, highlighting the role of gap topology.

Findings

Weak magnetic fields suppress surface superconductivity abruptly.

Bulk nodal state persists at higher magnetic fields.

Magnetic hysteresis indicates vortex dynamics.

Abstract

Selective spectroscopic disentanglement of surface and bulk quantum orders remains an outstanding challenge in condensed matter physics. The candidate topological superconductor PdTe has recently been proposed to host a nodeless surface gap on top of a nodal bulk state, but their direct identification and mutual coupling remained experimentally elusive. Here, we employ magnetic-field-dependent Andreev reflection spectroscopy to spectroscopically disentangle these components. At zero magnetic field, the spectra exhibit a BCS-like gap structure, consistent with dominant transport through a fully gapped surface superconducting state. Strikingly, even a weak magnetic field leads to an abrupt suppression of the Andreev-enhanced conductance (AEC), while a residual AEC, attributable to the nodal bulk state, persists to much higher magnetic fields. The transition is accompanied by pronounced magnetic hysteresis pointing to the existence of vortex dynamics at low fields. Our findings suggest that the nodal bulk gap facilitates early vortex entry, which in turn disrupts the fragile surface superconductivity. These results establish a field-tunable decoupling of surface and bulk superconductivity and illustrate how distinct gap topologies can shape the global superconducting order in multichannel systems.