Zero-bias peaks and splitting in an Al–InAs nanowire topological superconductor as a signature of Majorana fermions

Majorana fermions are the only fermionic particles that are expected to be their own antiparticles. While in high-energy physics the Majorana is an elementary particle, in condensed matter physics one of its manifestations is an emergent quasi-particle at zero energy state. These quasi-particles were predicted to exist in 1d at the two ends of a ‘p-wave’ or ‘topological superconductor’. In this talk I will show how we induce the topological phase in an InAs nanowire in proximity to an S-wave superconductor by the combination of spin-orbit coupling and external magnetic field. The signature of Majorana is verified by measuring distinct zero bias conductance peak (ZBP) in tunneling experiment. We contact the S-wave superconducting strip on a suspended InAs nanowire followed by a normal contact at the end of the nanowire; the barrier and the chemical potential are tuned using local and global gates. I will concentrate on the characteristics of the distinct ZBP, and its splitting in energy, both appearing only with a magnetic field applied perpendicular to spin-orbit direction. I will also show the dependence of the peak height and width on the system’s parameters, such as, chemical potential, magnetic field and its orientation, and the electrons’ temperature. While not providing a definite proof of a Majorana state, the experimental data strongly support its existence.

References:
‘Zero-bias peaks and splitting in an Al–InAs nanowire topological superconductor as a signature of Majorana fermions’
AnindyaDas, Yuval Ronen, Yonatan Most, Yuval Oreg, MotyHeiblum and HadasShtrikman.
Nature Physics, Published online: 11th November, 2012(arXiv:1205.7073).