Figure 2: Phase diagram of La1.8−xEu0.2SrxCuO4.
From: Unconventional charge order in a co-doped high-Tc superconductor
The intermediate phase, as obtained from NQR wipeout and specific heat, approximately follows the charge-stripe onset temperatures TCO (green circles, from resonant X-ray; ref. 31) for the samples investigated. The structural transition temperatures TLTT (grey diamonds) are from ref. 40 and significantly higher than either TCO or TEN. The transition temperatures TEN (red circles) are determined as the midpoint of the wipeout steps, with the error bars denoting the widths of the steps. These TEN from NQR agree with transition temperatures seen in specific heat, for two samples (empty triangles). The height of the wipeout plateau (empty squares) has a different trend with increasing Sr content, indicating that the intermediate phase disappears at a critical doping slightly above x=0.17, which approximately coincides with the critical tilt angle of Cu–O octahedra beyond which the tetragonal (LTT) phase is unstable. Error bars are s.d. from the means of the wipeout steps.
