Majorana or Not? An Insight from Atomic-Scale Shot-Noise

The search for non-abelian states of matter has become a central theme of modern quantum material research. The ability to identify and control such states is essential for developing fault-tolerant quantum computers. Notably, Majorana zero modes are of special interest, as they can serve as the foundation for topological qubits. A robust zero-bias conductance peak, observed in scanning tunneling spectra, is often regarded as the primary signature of a Majorana zero mode. Yet similar features can also arise from trivial bound states, raising a long-standing challenge of how to distinguish genuine Majoranas from imposters. In my talk, I will address this problem with a new approach, atomic-scale shot-noise spectroscopy, that goes beyond conductance measurements. Through a detailed investigation on multiple defect- and vortex-bound zero-bias states in the widely studied (putative) topological superconductor Fe(Se,Te), I will show that while differential conductance measurements might sometimes fail to detect an imposter Majorana state locally, noise measurements consistently provide a conclusive diagnostic, offering a powerful complementary probe. Looking ahead, this technique can be applied to other reported platforms, including end-localized zero modes in ferromagnetic atomic chains on superconductors and vortex cores in topological insulator-superconductor hybrids, to verify whether their Majorana-like signature in tunneling conductance can pass the shot-noise test.