Structure responsible for the superconducting state in La3Ni2O7 at low temperature and high pressure conditions
Luhong WangYan LiShengyi XieFuyang LiuHualei SunCaoxin HuangYang GaoTakeshi NakagawaBoyang FuBo DongZhenhui CaoRunze YuSaori I. KawaguchiHirokazu KadobayashiMeng Wang
Luhong WangYan LiShengyi Xie
Very recently, a new superconductor with Tc = 80 K was reported in nickelate (La3Ni2O7) at around 15 - 40 GPa conditions (Nature, 621, 493, 2023) , which is the second type of unconventional superconductor, beside the cuprates, with Tc above liquid nitrogen temperature. However, the phase diagram plotted in this report mostly based on the transport measurement at low temperature and high pressure conditions, and the assumed corresponding X-ray diffraction (XRD) results was carried out at room temperature. This encouraged us to carry out in situ low temperature and high pressure synchrotron XRD experiments to determine which phase is responsible for the high Tc state. In addition to the phase transition from orthorhombic Amam structure to orthorhombic Fmmm structure, a tetragonal phase with space group of I4/mmm was discovered at 40 K when compressed to 19 GPa at which the superconductivity takes palce in La3Ni2O7. This work sheds new lights to identify what is the most likely phase responsible for superconductivity in the double layered nickelate.