Majorana bound states in topological Josephson junctions

Much of modernmesoscopic physics focuses on studying hybrid superconducting structures: systems that combine superconductors with other materials such as semiconductors, ferromagnets, and graphene. When properly engineered, these devices display emergent physical properties that are absent in their individual constituents. An early example of such a device is the two-terminal Josephson junction: two superconducting terminals connected by a region without superconductivity. Josephson junctions give rise to a plethora of interesting phenomena, including quantized voltage steps and macroscopic quantum coherence. Experimental and theoretical advances in Josephson devices have led to numerous technological applications, such as sensitive magnetic field detectors, rapid single flux quantum logic, metrological voltage standards, and superconducting qubits.
Semiconductors with strong spin-orbit coupling proximitized with a superconductor are another prominent example of hybrid devices. Although semiconductors and conventional superconductors have been well understood for decades, their combination is predicted to yield a new state of matter known as topological superconductivity. Topological superconductors hostMajorana bound states: topologically protected quasiparticles with non-abelian statistics that are promising candidates to realize fault-tolerant qubits. Reliably creating and manipulating Majorana modes remains one of the outstanding challenges inmodern condensed matter physics.