NSRRC Activity Report 2023

022 NSRRC ACTIVITY REPORT 2023 charge order in heavily overdoped La 2 − x Sr x CuO 4 thin films beyond the superconducting dome. Figure 2 presents further experimental evidence for charge order correlation in heavily overdoped La 2−x Sr x CuO 4 thin films beyond the superconducting dome. The Cu L-edge resonant energy-integrated X-ray scattering (REIXS) results for La 2−x Sr x CuO 4 (LSCO) with various doping levels show that the charge order (CO) peak is nearly temperature independent up to 300 K. This provides additional evidence for the existence of charge order correlation in heavily overdoped La 2−x Sr x CuO 4 thin films beyond the superconducting dome, supporting the team’s argument that charge ordering behavior is dominant in the overdoped metallic regime. The figure also highlights the doping dependence of the CO wave vector and the nesting vector, providing insights into the underlying physics of the charge order correlation. The elastic intensity map and the inelastic RIXS intensity map along the ( H , 0 ) and ( H, H ) directions show the Fig. 2 : Cu L 3 edge and O K edge REIXS studies of charge order correlation in La 1.55 Sr 0.45 CuO 4 . (a) Observation of CO correlation along the (0, - K) direction at both the Cu L 3 edge and O K edge; offset is applied for clarity. (b) Polarization dependence of the CO peak, collected at 930 eV and L = 1.1 r.l.u. (c) Detuning measurements near the Cu L 3 edge after self-absorption corrections. (d) L dependence of CO correlation within the accessible range of [1.1, 1.8] r.l.u. at 930 eV, collected with σ polarization. [Reproduced from Ref. 1] anisotropic momentum dependence of phonon intensity and dispersive CO excitations in LSCO with x = 0.45, as shown in Fig. 3 . This result provides additional evidence for the existence of charge order correlation in heavily overdoped La 2 − x Sr x CuO 4 thin films and shows that charge ordering prevails in the overdoped metallic regime. This discovery challenges the conventional understanding of extremely overdoped cuprates as Fermi liquid metals without exotic electronic orders and suggests that charge order is prevailing in the overdoped metallic regime. The team suggests that the highly overdoped regime harbors unexplored and interesting physics that requires novel theoretical perspectives. The findings of this study provide a valuable perspective on the behavior of high-temperature superconductors at high doping levels and uncovers new avenues for exploring the competition between charge order states and superconductivity in a wide range of correlated electron systems. This experimental evidence challenges the conventional understanding of extremely overdoped cuprates as Fermi liquid metals without exotic electronic