Bulk superconductivity up to 96 K in pressurized nickelate single crystals

Abstract

Recently, the Ruddlesden–Popper bilayer nickelate La3Ni2O7 has emerged as a superconductor with a transition temperature (Tc) of approximately 80 K above 14 GPa (refs. 1–3). Achieving a higher Tc in nickelate superconductors, along with the synthesis of reproducible high-quality single crystals without relying on high-oxygen-pressure growth conditions, remains a significant challenge4–7. Here we report superconductivity up to 96 K under high pressure in bilayer nickelate single crystals synthesized at ambient pressure. Energy-dispersive spectroscopy, single-crystal X-ray diffraction, nuclear quadrupole resonance and scanning transmission electron microscopy evidenced high crystal quality of the flux-grown La2SmNi2O7−δ single crystals. La2SmNi2O7 exhibits clear bulk superconductivity, including zero resistivity ( $${T}_{{\rm{c}},\max }^{{\rm{onset}}}$$  = 92 K and $${T}_{{\rm{c}},\max }^{{\rm{zero}}}$$  = 73 K at 21.6 GPa) and the Meissner effect (Tc = 60 K at 20.6 GPa). A low-temperature high-pressure structural study indicates that both monoclinic and tetragonal structures can support superconductivity in this bilayer nickelate. Furthermore, we established a correlation between higher Tc under high pressures and larger in-plane lattice distortion under ambient conditions, corroborated by observing even higher $${T}_{{\rm{c}}}^{{\rm{onset}}}$$ of 96 K in La1.57Sm1.43Ni2O7−δ. This study overcomes key limitations in growing nickelate superconductor crystals, resolves the crystal structure in the superconducting state and demonstrates an effective pathway towards achieving higher Tc. Bulk superconductivity has been observed up to 96 K in pressurized bilayer nickelate single crystals which were synthesized under ambient pressure.