Evidence of topological superconductivity in planar Josephson junctions

• Published in: Nature (London) Vol. 569; no. 7754; pp. 89 - 92
• Main Authors: Fornieri, Antonio, Whiticar, Alexander M., Setiawan, F., Portolés, Elías, Drachmann, Asbjørn C. C., Keselman, Anna, Gronin, Sergei, Thomas, Candice, Wang, Tian, Kallaher, Ray, Gardner, Geoffrey C., Berg, Erez, Manfra, Michael J., Stern, Ady, Marcus, Charles M., Nichele, Fabrizio
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-05-2019; Nature Publishing Group
• Subjects: 639/766/119/1003; 639/766/119/2792; Aluminum; Analysis; Arsenic; Arsenides; Bias; Conductance; Confining; Control; Critical field (superconductivity); Dependence; Electric properties; Electrodynamics; Fault tolerance; Fermions; Heterostructures; Humanities and Social Sciences; Indium arsenides; Josephson junctions; Letter; Magnetic fields; Methods; multidisciplinary; Nanowires; Phase transitions; Quantum computing; Quantum electrodynamics; Resistance; Science; Science (multidisciplinary); Spectroscopic analysis; Spectroscopy; Spectrum analysis; Superconductivity; Superconductor junctions; Superconductors; Topological superconductors; Denmark
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-019-1068-8

Majorana zero modes—quasiparticle states localized at the boundaries of topological superconductors—are expected to be ideal building blocks for fault-tolerant quantum computing
1
,
2
. Several observations of zero-bias conductance peaks measured by tunnelling spectroscopy above a critical magnetic field have been reported as experimental indications of Majorana zero modes in superconductor–semiconductor nanowires
3
–
8
. On the other hand, two-dimensional systems offer the alternative approach of confining Majorana channels within planar Josephson junctions, in which the phase difference
φ
between the superconducting leads represents an additional tuning knob that is predicted to drive the system into the topological phase at lower magnetic fields than for a system without phase bias
9
,
10
. Here we report the observation of phase-dependent zero-bias conductance peaks measured by tunnelling spectroscopy at the end of Josephson junctions realized on a heterostructure consisting of aluminium on indium arsenide. Biasing the junction to
φ
 ≈ π reduces the critical field at which the zero-bias peak appears, with respect to
φ
 = 0. The phase and magnetic-field dependence of the zero-energy states is consistent with a model of Majorana zero modes in finite-size Josephson junctions. As well as providing experimental evidence of phase-tuned topological superconductivity, our devices are compatible with superconducting quantum electrodynamics architectures
11
and are scalable to the complex geometries needed for topological quantum computing
9
,
12
,
13
.
Evidence is found for phase-tunable Majorana zero modes in scalable two-dimensional Josephson junctions produced by top-down fabrication.