Which La_3Ni_2O_7 polymorph carries bulk superconductivity under pressure? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title · changed
Revision 1: Which La3Ni2O7 polymorph carries bulk superconductivity under pressure
Revision 2: Which $\mathrm{La_3Ni_2O_7}$ polymorph carries bulk superconductivity under pressure?
Plain · changed
Revision 1: Early pressure experiments found only a small superconducting volume, and La3Ni2O7 crystals contain two stacking patterns of nickel-oxide layers, so which structure superconducts in bulk was unclear.
Revision 2: Early pressure experiments found only a small superconducting volume, and $\mathrm{La_3Ni_2O_7}$ crystals contain two stacking patterns of nickel-oxide layers, so which structure superconducts in bulk was unclear.
Precise · changed · core
Revision 1: Determine which structural polymorph of La3Ni2O7 at high pressure (bilayer 2222 or alternating monolayer-trilayer 1313) carries the $\sim 80\,\mathrm{K}$ superconductivity, and whether the superconducting volume fraction in phase-pure stoichiometric crystals is bulk. An answer combines diffraction under pressure with ac susceptibility volume fractions on the same phase-pure samples.
Revision 2: Determine which structural polymorph of $\mathrm{La_3Ni_2O_7}$ at high pressure (bilayer 2222 or alternating monolayer-trilayer 1313) carries the $\sim 80\,\mathrm{K}$ superconductivity, and whether the superconducting volume fraction in phase-pure stoichiometric crystals is bulk. An answer combines diffraction under pressure with ac susceptibility volume fractions on the same phase-pure samples.
Settled by
Shielding-fraction measurements near 100 percent on phase-pure samples of each polymorph with simultaneous structural determination.
Kind
well-posed
Answer type
identification
References
(empty)
Literature status
partially-resolved
Status note · changed
Revision 1: Bulk superconductivity was reported in La2PrNi2O7 under pressure (2024) and in pressurized bilayer nickelate crystals up to about $96\,\mathrm{K}$ (2025), and superconductivity was also reported in the 1313 polymorph (2025).
Revision 2: Bulk superconductivity was reported in $\mathrm{La_2PrNi_2O_7}$ under pressure (2024) and in pressurized bilayer nickelate crystals up to about $96\,\mathrm{K}$ (2025), and superconductivity was also reported in the 1313 polymorph (2025).
Posed since
2023

Decisions