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6952121 
Journal Article 
Unconventional superconductivity in the single-atom-layer alloy Si(111)-root 3 x root 3-(Tl, Pb) 
Nakamura, T; Kim, H; Ichinokura, S; Takayama, A; Zotov, A; Saranin, AA; Hasegawa, Y; Hasegawa, S; , 
2018 
AMER PHYSICAL SOC 
COLLEGE PK 
WOS:000447463700006 
We present results of low-temperature scanning tunneling microscopy/spectroscopy measurements on the one-atom-layer superconductor, Si(111)-root 3 x root 3-(Tl, Pb) which has a spin-split band structure due to the Rashba-Bychkov effect. It was revealed that it has a multiple superconducting gap Delta with significant anisotropy and sizable magnitude of 2 Delta/k(B)T(C) similar to 8.6 (k(B) is the Boltzmann constant and T-C is the critical superconducting temperature). Under the magnetic field, a dip structure was observed even at the core of the vortex. The dip structure was like a "pseudogap" because it remained up to 2 T, well above the upper critical magnetic field determined in the transport measurements (similar to 0.7 T). This unconventional behavior suggests the possibility of spin-triplet Cooper pairs related to parity-broken superconductors.