Charge order in the overdoped region of the cuprate superconductor La2-xCaxCuO4

Understanding the mechanism behind high-temperature superconductivity in the layered copper-oxide superconductors has been a major challenge in condensed matter physics [1]. The complexity arises from the many different collective fluctuations that are observed throughout the phase diagram [1]. Among these, charge density wave (CDW) order has found prominence as a possible competing order against superconductivity, given its temperature dependence and that it is universally observed in all cuprate superconductors [2]. However, most early studies observed the disappearance of CDW just above optimal doping and well below the doping at which superconductivity disappears [2]. This brought into question the role of CDW in shaping the superconducting dome of the cuprates. Intriguingly, several recent studies in overdoped cuprates (Bi,Pb)2.12Sr1.88CuO6+δ (Bi2201) [3], La2-xSrxCuO4 (LSCO) [4] and Tl2Ba2CuO6+δ (Tl2201) [5] have found the existence of CDW in the overdoped regime, thus reviving the question of CDW as an order competing against superconductivity also on the overdoped side of the phase diagram. In this talk, I will report on our resonant x-ray scattering investigation of CDW order in highly overdoped LaxCaxCuO4 (LCCO) thin films. We find that CDW order persists well into the overdoped regime and displays rather unique temperature and doping dependences, likely connected to the lower doping-induced structural disorder resulting from nearly identical radii of La and Ca.

[1] B. Keimer et al., Nature 518, 179 (2015)
[2] A. Frano et al., J. Phys. Cond. Matt. 32, 374005 (2020)
[3] Y. Y. Peng et al., Nat. Mater. 17, 697 (2018)
[4] H. Miao et al., npj Quantum Materials 6, 31 (2021)
[5] C. C. Tam et al., Nat. Commun. 13, 570 (2022)