Polyhydride superconductors have been shown to possess metallic properties with a Bardeen-Cooper-Schrieffer-type superconducting ground state. Here, we provide evidence for unconventional transport associated with a pseudogap phase in cubic cerium superhydride CeH10 (TC = 116 K) at pressure of 115-125 GPa. A large negative magnetoresistance in the non-superconducting state below 90 K, quasi T-linear electrical resistance, and a sign-change of its temperature dependence mark the emergence of this phase. We studied the magnetic phase diagrams and the upper critical fields BC2(T) of CeH10, CeH9, and CeD9 in pulsed fields up to 70 T. BC2(T) of CeH9 and CeD9 exhibits pronounced saturation at low temperatures in accordance with the Werthamer-Helfand-Hohenberg model, whereas CeH10 stands out in particular, as it does not obey this model. Our observations, therefore, reveal the unconventional nature of non-superconducting state of cerium superhydride CeH10.
@article{arxiv.2307.11742,
title = {Evidence for Pseudogap Phase in Cerium Superhydrides: CeH$_{10}$ and CeH$_9$},
author = {Dmitrii Semenok and Jianning Guo and Di Zhou and Wuhao Chen and Toni Helm and Alexander Kvashnin and Andrei Sadakov and Oleg Sobolevsky and Vladimir Pudalov and Chuanying Xi and Xiaoli Huang and Ivan Troyan},
journal= {arXiv preprint arXiv:2307.11742},
year = {2023}
}