Violation of Pauli paramagnetic limit and topological transition in Al nanofilms grown by molecular beam epitaxy

Ching-Chen Yeh^1*, Guan-Ming Su¹, Bi-Yi Wu¹, Yu-Chen Yeh¹, Chih-Yuan Wang¹, Wei-Ren Syong¹, Yen-Ting Fan², Sheng-Di Lin², Lee Chow³, Chi-Te Liang¹

¹Physics, National Taiwan University, Taipei, Taiwan
²Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan
³Physics, University of Central Florida, Orlando, FL, USA

* Presenter:Ching-Chen Yeh, email:mu293937@gmail.com

In this work, we report extensive transport measurements on Al nanofilms on GaAs (as-grown thickness ranging from 3 nm to 4 nm) grown by molecular beam epitaxy (MBE). Such MBE-grown Al nanofilms exhibit outstanding properties: a higher critical temperature (around 2.2 K, depending on the thickness) compared to that of bulk aluminum (1.2 K) and a high critical magnetic field which goes beyond the Pauli paramagnetic limit in the thinnest sample (3-nm thick). We also observed the Berezinskii-Kosterlitz-Thouless (BKT) transition, a topological transition in two dimensions.

Keywords: Superconductivity, Pauli paramagnetic limit, Topological transition, Aluminum nanofilms