Electronic structures and multi-orbital models of La3Ni2O7 thin films at ambient pressure

Abstract The recent discovery of superconductivity with a transition temperature T c exceeding 40 K in La 3 Ni 2 O 7 and (La, Pr) 3 Ni 2 O 7 thin films at ambient pressure marks a significant breakthrough in the field of nickelate superconductors. Using density functional theory (DFT), we propose a double-stacked two-orbital effective model for La 3 Ni 2 O 7 thin film based on the Ni − e g orbitals. Our analysis of the Fermi surface reveals three electron pockets ( $$\alpha ,{\alpha }^{{\prime} },\beta$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>α</mml:mi> <mml:mo>,</mml:mo> <mml:msup> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>,</mml:mo> <mml:mi>β</mml:mi> </mml:math> ) and two hole pockets ( $$\gamma ,{\gamma }^{{\prime} }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>γ</mml:mi> <mml:mo>,</mml:mo> <mml:msup> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> ), where the additional $${\alpha }^{{\prime} }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> and $${\gamma }^{{\prime} }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> </mml:math> pockets arise from inter-stack interactions. Furthermore, we introduce a high-energy model that incorporates O− p orbitals to facilitate future studies. Calculations of spin susceptibility within the random phase approximation (RPA) indicate that magnetic correlations are enhanced by nesting of the γ pocket, which is predominantly derived from the Ni $$-{d}_{{z}^{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>−</mml:mo> <mml:msub> <mml:mrow> <mml:mi>d</mml:mi> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> orbital. Our results provide a theoretical foundation for understanding the electronic and magnetic properties of La 3 Ni 2 O 7 thin films.