Momentum-space imaging of Cooper pairing in a half-Dirac-gas topological superconductor

• Published in: Nature physics 2014-12, Vol.10 (12), p.943-950
• Main Authors: Xu, Su-Yang, Alidoust, Nasser, Belopolski, Ilya, Richardella, Anthony, Liu, Chang, Neupane, Madhab, Bian, Guang, Huang, Song-Hsun, Sankar, Raman, Fang, Chen, Dellabetta, Brian, Dai, Wenqing, Li, Qi, Gilbert, Matthew J., Chou, Fangcheng, Samarth, Nitin, Hasan, M. Zahid
• Format: Article
• Language: English
• Subjects: 140/146; 639/301/119/1003; 639/766/119/2792; 639/766/119/544; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Degrees of freedom; Electrons; Imaging; Mathematical analysis; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Platforms; Quantum physics; Studies; Superconductivity; Superconductors; Supersymmetry; Theoretical; Topology; Two dimensional
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys3139

Superconductivity involving topological Dirac electrons has recently been proposed as a platform between concepts in high-energy and condensed-matter physics. It has been predicted that supersymmetry and Majorana fermions, both of which remain elusive in particle physics, may be realized through emergent particles in these particular superconducting systems. Using artificially fabricated topological-insulator–superconductor heterostructures, we present direct spectroscopic evidence for the existence of Cooper pairing in a weakly interacting half Dirac gas. Our studies reveal that two dimensional topological superconductivity in a helical Dirac gas is distinctly different from that in an ordinary two-dimensional superconductor in terms of the spin degrees of freedom of electrons. We further show that the pairing of Dirac electrons can be suppressed by time-reversal symmetry-breaking impurities, thereby removing the distinction. Our demonstration and momentum-space imaging of Cooper pairing in a half-Dirac-gas two-dimensional topological superconductor serve as a critically important platform for future testing of fundamental physics predictions such as emergent supersymmetry and topological quantum criticality. Supersymmetry and Majorana fermions that are their own antiparticles are both concepts from particle physics that may become testable in condensed-matter systems. The observation of Cooper pairs in a helical Dirac gas brings this goal a step closer.