Abstract

I will present how high-pressure research provides insight into optimising superconductivity. I will present studies of hydride superconductors, where high-energy lattice phonons couple to hydrogen orbitals in structures stabilised at very high pressures only. Record superconductivity has been discovered in H3S , LaH10, YH9 , and other hydride compounds [1–3]. However, experimental studies of superconductivity in hydrides remain an enormous challenge. We have characterised superconductivity in H3S and we have discovered the new superconductor La4H23 [4]. These measurements have been made possible through developments of robust thin-film methods for high-pressure research. In TiSe2, we observe a dome of superconductivity around the quantum critical point of the charge-density-wave order [5]. We show that superconductivity only emerges once a Lifshitz transition releases electron and hole pockets connected by the wave vector of the charge order. This suggests s± superconductivity mediated by CDW fluctuations analogue to some of the iron pnictide superconductors.

[1] Kong, P. et al. Nature Communications 12, 5075 (2021).

[2] Somayazulu, M. et al. Phys. Rev. Lett. 122, 027001 (2019).

[3] Drozdov, A. P. et al. Nature 525, 73 (2015).

[4] Cross, S. et al. Phys. Rev. B 109 , L020503 (2024).

[5] Hinlopen, R. D. H. et al. arXiv:2308.02475 (2023).