Electronic correlations, layer distinction, and electron doping in the alternating single-layer trilayer La₃Ni₂O₇ polymorph

We employ a density-functional theory plus dynamical mean-field theory framework to investigate the correlated electronic structure of the alternating single-layer trilayer (1313) polymorph of La₃Ni₂O₇ under pressure. We find that La₃Ni₂O₇-1313 exhibits electronically distinct layers in terms of their correlations. At ambient pressure, the single-layer is in a Mott insulating regime and the low-energy physics is dominated by the trilayer block. Under pressure, the single-layer exhibits orbital-selective physics closing the gap allowing charge flow into the trilayer block. This change in effective doping of the trilayer block is likely linked to the higher Tc obtained in La₃Ni₂O₇-1313 (~ 80 K) when compared to the nominal trilayer La₄Ni₃O₁₀ (~ 30 K). We conclude that correlation-driven layer differentiation is crucial in the La₃Ni₂O₇-1313 polymorph and that its low-energy physics aligns closely with the trilayer La₄Ni₃O₁₀ (rather than the conventional bilayer La₃Ni₂O₇), in spite of the apparent differences in nominal filling.