Elastic Moduli of detwinned orthorhombic optimally doped LSCO (La$_{2-0.16 }$Sr$_{ 0.16 }$CuO$_{4})$

Accurate elastic modulus characterization of the superconducting phase transition (SC) in La$_{2-0.16 }$Sr$_{ 0.16 }$CuO$_{4}$ is difficult because the discontinuities in moduli are much smaller than fluctuations from twin boundary motion. Thus detwinning is required for a useful measurement and was achieved using mechanical stress along the tetragonal [110] direction (or equivalently, along the orthorhombic [100] direction) below the orthorhombic phase transition that is well below ambient temperature. Using resonant ultrasound spectroscopy (RUS) on the detwinned monocrystal, the discontinuities and moduli around the SC transition were measured.