Negative Oxygen Isotope Effect on the Static Spin Stripe Order in Superconducting La₂−_xBa_xCuO₄(x=1/8) Observed by Muon-Spin Rot

Large negative oxygen-isotope (¹⁶O and ¹⁸O) effects (OIEs) on the static spin-stripe-ordering temperature T_so and the magnetic volume fraction V_m were observed in La_2−xBa_xCuO₄(x=1/8) by means of muon-spin-rotation experiments. The corresponding OIE exponents were found to be α_Tso=-0.57(6) and α_Vm=-0.71(9), which are sign reversed to α_TC=0.46(6) measured for the superconducting transition temperature T_c. This indicates that the electron-lattice interaction is involved in the stripe formation and plays an important role in the competition between bulk superconductivity and static stripe order in the cuprates.