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Pb, Au, superconductivity, Au-plumbene, spin-orbit coupling, angle-resolved photoemission spectroscopy
NSRRC User Shu-Jung Tang's Collaborative Research Published in Advanced Science
Au deposited on Pb(111) surface forms as a PbAu alloy layer covered with an Au Kagome layer, which exhibits enhanced superconductivity and Rashba effects.
Bulk Pb is a conventional superconductor with transition temperature Tc up to 7 K. Prof. Shu-Jung Tang in physics at National Tsing Hua University, who is a long-term user and also an adjunct scientist of the NSRRC, and Prof. Chun-Liang Lin in electrophysics at National Yang Ming Chiao Tung University collaborate with each other to demonstrate that a layer of Au atoms deposited onto Pb(111) surface yet enhances Tc to 7.4 K, breaking up the proximity-effect picture based on the conventional superconductivity theory established 60–70 years ago. Moreover, due to the heavy masses of both Pb and Au atoms, the formation of the PbAu alloy induces large electron spin-orbit coupling, manifesting itself as a 2D novel material possessing both enhanced superconductivity and electron spin properties. This special 2D material is proved to be an Au-plumbene with buckled honeycomb lattice, covered by an Au Kagome layer.

The discovery of graphene with honeycomb lattice in 2004 has brought great impact to science and industry. Since then, it has been a challenging task to form new 2D materials with honeycomb lattice from different elements, the so-called xene families, for scientists. The research team had been worldly recognized for their pioneering work on germanene and silicene, respectively. They worked together to produce the first 2D xene with dual novel properties, Au-plumbene, in Taiwan. The results were published in the top journal Advanced Science on May 3, 2023. All the electronic energy band structures presented in the research were taken by angle-resolved photoemission spectroscopy at TLS 21B1 of the NSRRC.