In Search of Majorana Pair Along The Golden Path

Jagadeesh Moodera

One of the excellent examples for the topologically driven nontrivial quantum phenomena is the prediction of Majorana zero modes (MZMs or the Majorana pair) to occur in a topological superconductor (TSC) – viz., superconducting surface state of gold. [1] MZMs form when a fermion splits in a TSC into two parts well separated in space, and thus always appear in pair together with its partner. Each of the Majorana pair is an antiparticle of itself. Potter and Lee, [1] predicted that under the right conditions, a superconducting gold nanowire with (111) crystalline surface with its large Rashba spin-orbit (S-O) splitting could host the Majorana pair. In search of this golden pair, creating the needed topological superconductivity and Zeeman field in carefully optimized Au (111) surface we laid the foundation to realize MZM. [2] We experimentally achieved the needed novel stable heterostructures, to directly observe the MZM pair using a low temperature with high vector field scanning tunneling microscope - probing the superconducting gold surface having ferromagnetic EuS nano islands (that provides the crucial internal exchange field). [3] This success opens many questions about the Majorana properties enabling plenty opportunities for future investigations. Through this two-dimensional stable metal platform, with induced superconductivity of the Shockley surface states (SS) of (111)-gold (Au), we can envision a scalable system for building non-local qubits that are intrinsically fault-tolerant. In this talk I will be presenting our path towards the observation of MZMs.

[1] A. C. Potter & P. A. Lee PRL 105, 227003 (2010); PRB 85, 094516 (2012)
[2] Peng Wei, Sujit Manna, Marius Eich, Patrick Lee and J. S. Moodera, Phys. Rev. Lett. 122, 247002 (2019)
[3] Sujit Manna, Peng Wei, Yingming Xie, Kam Tuen Law, Patrick A. Lee and Jagadeesh S. Moodera, Proc. Natl. Acad. Sci. 117 (16) 8775-8782 (Apr. 21, 2020)