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Ultrafast Renormalization of the On-Site Coulomb Repulsion in a Cuprate Superconductor
Physical Review X  (IF15.762),  Pub Date : 2022-01-20, DOI: 10.1103/physrevx.12.011013
Denitsa R. Baykusheva, Hoyoung Jang, Ali A. Husain, Sangjun Lee, Sophia F. R. TenHuisen, Preston Zhou, Sunwook Park, Hoon Kim, Jin-Kwang Kim, Hyeong-Do Kim, Minseok Kim, Sang-Youn Park, Peter Abbamonte, B. J. Kim, G. D. Gu, Yao Wang, Matteo Mitrano

Ultrafast lasers are an increasingly important tool to control and stabilize emergent phases in quantum materials. Among a variety of possible excitation protocols, a particularly intriguing route is the direct light engineering of microscopic electronic parameters, such as the electron hopping and the local Coulomb repulsion (Hubbard $U$). In this work, we use time-resolved x-ray absorption spectroscopy to demonstrate the light-induced renormalization of the Hubbard $U$ in a cuprate superconductor, ${\mathrm{La}}_{1.905}{\mathrm{Ba}}_{0.095}{\mathrm{CuO}}_{4}$. We show that intense femtosecond laser pulses induce a substantial redshift of the upper Hubbard band while leaving the Zhang-Rice singlet energy unaffected. By comparing the experimental data to time-dependent spectra of single- and three-band Hubbard models, we assign this effect to an approximately 140-meV reduction of the on-site Coulomb repulsion on the copper sites. Our demonstration of a dynamical Hubbard $U$ renormalization in a copper oxide paves the way to a novel strategy for the manipulation of superconductivity and magnetism as well as to the realization of other long-range-ordered phases in light-driven quantum materials.