In condensed matter, Majorana bound states (MBSs) are predicted to obey exotic non-Abelian statistic and can be exploited for fault-tolerant qubits. Theoretical works suggested MBSs can be created by engineering topological superconductor based on one-dimensional semiconductor with spin-orbit coupling in contact with a conventional s-wave superconductor. Significant experimental effort has since then been dedicated to this system. While many results are encouraging, recently there are major concerns about disorder, small topological gap which effectively creates a competition with trivial Andreev bound state physics mimicking some of these observations.
In this talk, I will first present our effort to engineer MBSs in hybrid superconductor/semiconductor nanowire systems. We observed stable zero bias peaks (ZBPs) at finite fields as a possible signature of MBSs and mapped out a phase diagram of the ZBPs, which is consistent with calculations for a finite-length topological nanowire. While the observation is promising, we noticed topologically trivial states are rather generic in nanowire systems and can mimic most of the behaviors of MBSs. To better identify MBSs, we fabricate three-terminal nanowire devices in the Majorana configuration, allowing tunnelling measurements across both nanowire ends. We demonstrate the three-terminal geometry offers a new way to identify non-Majorana states even if local two-terminal measurements are consistent with MBSs. Moreover, the identification of delocalized states enables us to estimate the disorder strength in our systems.
In the last part of the talk, I will discuss planar Josephson junction built on two-dimensional electron gas (2DEG) with strong spin-orbit coupling and induced superconductivity as another promising platform for realizing MBSs and topological superconductivity. Apart from ZBPs, we searched for other signals of topological superconductivity in this system. To make the Josephson system more hospitable to MBSs, we explored different junction geometries and observed enhanced supercurrent and enhanced diode effect efficiency under the presence of a periodic potential.
The speaker received his PhD at University of Pittsburgh, specializing in hybrid semiconductor-superconductor systems. His research mainly focuses on topological superconductivity and Majorana bound states at interfaces of hybrid superconductor-semiconductor systems. He also has a broad interest in nanoscale physics with emphasis on new materials/device development for quantum information. Now a postdoctoral researcher at New York University, he is working closely with material scientists to explore planar Josephson junction built on two-dimensional electron gas as the platform for Majorana bound states and topological superconductivity. His achievements have been featured in journals such as Nature Physics, Science Advances and Physical Review Letters.
Tencent Meeting link: https://meeting.tencent.com/dm/08SjxY4bpsl6 Meeting ID: 365742662