In a clean high-Tc superconductor you do not see the gap.
Kamarás K, Herr SL, Porter CD, Tache N, Tanner DB, Etemad S, Venkatesan T, Chase E, Inam A, Wu XD, Hegde MS, Dutta B.
Kamarás K, et al. Among authors: tache n.
Phys Rev Lett. 1990 Jan 1;64(1):84-87. doi: 10.1103/PhysRevLett.64.84.
Phys Rev Lett. 1990.
PMID: 10041279
No abstract available.