Strain-engineering Mott-insulating La2CuO4

• Published in: Nature communications Vol. 10; no. 1; p. 786
• Main Authors: Ivashko, O., Horio, M., Wan, W., Christensen, N. B., McNally, D. E., Paris, E., Tseng, Y., Shaik, N. E., Rønnow, H. M., Wei, H. I., Adamo, C., Lichtensteiger, C., Gibert, M., Beasley, M. R., Shen, K. M., Tomczak, J. M., Schmitt, T., Chang, J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.02.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1003; 639/766/119/997; Compressive properties; Cuprates; Electrons; Exchanging; Humanities and Social Sciences; Inelastic scattering; multidisciplinary; Optimization; Science; Science (multidisciplinary); Spectroscopy; Substrates; Thin films; Titanium; Transition temperature; Transition temperatures; Unconventional superconductivity; X ray absorption; X-ray scattering
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08664-6

The transition temperature T c of unconventional superconductivity is often tunable. For a monolayer of FeSe, for example, the sweet spot is uniquely bound to titanium-oxide substrates. By contrast for La 2−x Sr x CuO 4 thin films, such substrates are sub-optimal and the highest T c is instead obtained using LaSrAlO 4 . An outstanding challenge is thus to understand the optimal conditions for superconductivity in thin films: which microscopic parameters drive the change in T c and how can we tune them? Here we demonstrate, by a combination of x-ray absorption and resonant inelastic x-ray scattering spectroscopy, how the Coulomb and magnetic-exchange interaction of La 2 CuO 4 thin films can be enhanced by compressive strain. Our experiments and theoretical calculations establish that the substrate producing the largest T c under doping also generates the largest nearest neighbour hopping integral, Coulomb and magnetic-exchange interaction. We hence suggest optimising the parent Mott state as a strategy for enhancing the superconducting transition temperature in cuprates. The optimal condition for superconductivity is a long-sought issue but remains challenging. Here, Ivashko et al. demonstrate that the compressive strain to La 2 CuO 4 films enhances the Coulomb and magnetic-exchange interactions relevant for superconductivity, providing a strategy to optimise the parent Mott state for superconductivity.