Orateur
Description
Two-dimensional superconductors should exhibit a Berezinskii–Kosterlitz–Thouless (BKT) transition, and the 𝑇-dependence of the superfluid stiffness should distinguish between nodal or gapped order parameter symmetries. However, this picture dramatically changes when large scale inhomogeneities and spatially correlated disorder are taken into account, washing out BKT signatures. At the same time, superconducting percolative transitions can give rise to apparent unconventional features.
Random resistor and random impedance network (RRN/RIN) [1,2] models capture this phenomenology, naturally explaining features such as residual resistivity [1], non-linear IV characteristics [3], and unconventional stiffness [4,5].
In twisted multilayer graphene, we use elasticity theory to show how single site impurities can generate twist angle inhomogeneities. By mapping them into their corresponding local critical temperatures, we compute their finite-frequency conductance with the RIN.
Our calculations are consistent with recent microwave transport experiments [6,7,8] and gives a quantitative explanation of the reproducibility issues reported in twisted bilayer graphene devices [9]. Moreover, we identify the real part of the conductivity to be a key diagnostic observable to probe the relevance of correlated disorder.
References:
[1] G. Venditti, I. Maccari, M. Grilli, and S. Caprara, Condens. Mat. 5(2) (2020)
[2] G. Venditti, I. Maccari, M. Grilli, and S. Caprara, Nanomat. 11(8) (2021)
[3] G. Venditti, J. Biscaras, S. Hurand, N. Bergeal, J. Lesueur, A. Dogra, R. C. Budhani, Mintu Mondal, John Jesudasan, Pratap Raychaudhuri, S. Caprara, and L. Benfatto, Phys. Rev. B 100 (2019) 064506.
[4] G. Venditti, I. Maccari, A. Jouan, G. Singh, R. C. Budhani, C. Feuillet-Palma, J. Lesueur, N. Bergeal, S. Caprara, M. Grilli, SciPost Phys. 15 239 (2023)
[5] I. Maccari, L. Rademaker, G. Venditti, How twist angle inhomogeneity masks the BKT transition and the order parameter symmetry, arXiv: 2606.17191 (2026)
[6] J. M. Park et al., Science 10.1126/science.adv8376 (2025)
[7] Banerjee et al,Nature 638, 93–98 (2025)
[8] Mukherjee et al, Nature Materials 24, 1400–1406 (2025)
[9] Chun Ning Lau et al, Nature 602 41-50 (2022)