Charge density wave fluctuations in La_2-x Sr_x CuO₄ and their competition with superconductivity

We report hard (14 keV) x-ray diffraction measurements on three compositions (x=0.11,0.12,0.13) of the high-temperature superconductor La2−xSrxCuO4. All samples show charge density wave (CDW) order with onset temperatures in the range 51–80 K and ordering wave vectors close to (0.23,0,0.5). The CDW is strongest with the longest in-plane correlation length near 1/8 doping. On entering the superconducting state the CDW is suppressed, demonstrating the strong competition between the charge order and superconductivity. CDW order coexists with incommensurate magnetic order and the wave vectors of the two modulations have the simple relationship δcharge=2δspin. The intensity of the CDW Bragg peak tracks the intensity of the low-energy (quasielastic) spin fluctuations. We present a phase diagram of La2−xSrxCuO4 including the pseudogap phase, CDW, and magnetic order.