Emergent Zeeman-Resilient Superconductivity Beyond the Spin-Paramagnetic Limit in Ultrathin NiBi3

arXiv (Cornell University)

Abstract

The spin-paramagnetic limit sets a fundamental magnetic-field bound for conventional superconductors. Here we show that ultrathin NiBi$_3$ films develop a highly field-resilient superconducting state, with in-plane critical fields surpassing the spin-paramagnetic limit even above 0.9T$_C$. This enhancement is activated by dimensional confinement and depends sensitively on film thickness and morphology. Standard mechanisms, including strong spin-orbit coupling and multiband superconductivity, fail to quantitatively explain the observed robustness. These findings uncover an unconventional pathway for Zeeman-resistant superconductivity in low-dimensional materials beyond known Ising and Rashba scenarios, and further support earlier theoretical predictions of triplet pairing in low-dimensional NiBi$_3$.

Authors 7

1. Gabriel Sant’ana Aachen Kamerlingh Onnes-Huygens Laboratory

   Leiden University · Universidade Federal do Rio Grande do Sul · Huygens Institute for History and Culture of the Netherlands

   Affiliation as printed

   Instituto de Física , Universidade Federal do Rio Grande do Sul , 91501-970 Porto Alegre , Brazil

   Kamerlingh Onnes-Huygens Laboratory , Leiden University , P.O. Box 9504 , 2300 RA Leiden , The Netherlands

2. Leonardo Pessoa da Silva

   Universidade Federal do Rio Grande do Sul

   Affiliation as printed

   Instituto de Física , Universidade Federal do Rio Grande do Sul , 91501-970 Porto Alegre , Brazil

3. P. Schio

   Brazilian Center for Research in Energy and Materials

   Affiliation as printed

   Centro Nacional de Pesquisa em Energia e Materiais , CP 6192 , 13083-970 Campinas , SP , Brazil

4. David Möckli

   Universidade Federal do Rio Grande do Sul

   Affiliation as printed

   Instituto de Física , Universidade Federal do Rio Grande do Sul , 91501-970 Porto Alegre , Brazil

5. J. Aarts Aachen Kamerlingh Onnes-Huygens Laboratory

   Leiden University · Huygens Institute for History and Culture of the Netherlands

   Affiliation as printed

   Kamerlingh Onnes-Huygens Laboratory , Leiden University , P.O. Box 9504 , 2300 RA Leiden , The Netherlands

6. Kaveh Lahabi Aachen Kamerlingh Onnes-Huygens Laboratory

   Leiden University · Huygens Institute for History and Culture of the Netherlands

   Affiliation as printed

   Kamerlingh Onnes-Huygens Laboratory , Leiden University , P.O. Box 9504 , 2300 RA Leiden , The Netherlands

7. Milton A. Tumelero

   Universidade Federal do Rio Grande do Sul

   Affiliation as printed

   Instituto de Física , Universidade Federal do Rio Grande do Sul , 91501-970 Porto Alegre , Brazil