Detecting and Distinguishing Majorana Modes through Atomic Scale Shot Noise

An exciting area of research in quantum condensed matter physics involves the exploration of Majorana bound states (MBS) to create topologically protected qubits for fault-tolerant quantum computing.

In the quest for experimental evidence of these quasiparticles, the most frequently observed indication of MBS is considered as a peak in the differential conductance spectra at zero bias voltage.

While this observation could be easily detected in scanning tunneling microscopy/spectroscopy experiments, it does not serve as a piece of conclusive evidence for the Majorana nature of a state as other topologically trivial bound states, such as Yu-Shiba-Rusinov states, can also exhibit the same zero-bias conductance peak.

In this direction, recent theoretical investigations have extensively examined how shot noise at atomic could serve as a distinctive tool to differentiate between MBS and trivial bound states in vortex matter and nanowires.

However, experimental verification of these theories has not been feasible so far due to the underlying challenge of measuring shot noise with high enough sensitivity at a nanometer resolution.

Although experimentally challenging, in this project we will combine atomically resolved differential conductance and shot noise together by using a home-built shot-noise scanning tunneling microscope (SN-STM).

The unprecedented power of this technique will be exploited to measure shot noise which provides direct evidence to distinguish the MBS from any conventional in-gap mode.

We propose to investigate a couple of different scenarios such as single atomic impurities and vortex cores in a variety of iron-based superconducting quantum material, magnetic nanostructure (1D chains) coupled to an s-wave superconductor.