Study of superconducting properties in two-dimensional Pb₂Au honeycomb-like Moiré superlattice

Truc Nhu Huynh^1*, Ka-Weng Lei¹, Nitin Kumar¹, Kuan-Ying Song¹, Deepan Beja¹, Yu-Yao Hsu¹, Pin-Jui Hsu¹, Shu-Jung Tang^1,2

¹Physics, National Tsing Hua University, Hsinchu, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu, Taiwan

* Presenter:Truc Nhu Huynh, email:htnhunthu@gmail.com

Enhancement of critical temperature (T_c) in superconductivity is a momentous topic due to its essential applications. In recent years, multigap superconductors have been studied for the enhanced T_c. Moreover, multigap superconductors are proposed to be a new type of superconductors (intertype) and have many interesting physical properties related to particle physics. Based on theorical calculation, Pb₂Au alloy is predicted to have multigap superconductivity below 4K. Hence, it is a potential multigap superconductor candidate material. Knudsen cell evaporator was used to deposit Au to form a uniform structure on Pb(111) at room temperature (RT). Using low energy electron diffraction (LEED), scanning tunneling microcopy (STM), and angle-resolved photoemission spectroscopy (ARPES), we discovered that Au deposition on Pb(111) at different coverages lead to different surface structures, including an interesting Au nanoribbons phase. In this work, we focus on studying the superconducting properties of Au honeycomb-like structure on the top of Pb₂Au alloy at two different coverages at the temperature below T_c. Moiré superlattice and Au-honeycomb-like structure are observed on the top of Pb₂Au alloy with lattice constant of 7.4 nm and 5.9 Å, respectively. Furthermore, the temperature-dependent evolution of superconducting gap and quasiparticle interference are examined by scanning tunneling spectroscopy (STS) and STM from 0.4K to 10K.

Keywords: multigap superconductivity, intertype, Pb₂Au alloy, Au honeycomb-like structure