Electronic structure and magnetic tendencies of trilayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>La</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mi>Ni</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>10</mml:mn></mml:msub></mml:mrow></mml:math> under pressure: Structural transition, molecular orbitals, and layer differentiation
Harrison LaBollita, Jesse Kapeghian, M. R. Norman, Antía S. Botana
Abstract
Motivated by the recent observation of superconductivity in the pressurized trilayer Ruddlesden-Popper (RP) nickelate ${\mathrm{La}}_{4}{\mathrm{Ni}}_{3}{\mathrm{O}}_{10}$, we explore its structural, electronic, and magnetic properties as a function of hydrostatic pressure from first-principles calculations. We find that an orthorhombic (monoclinic)-to-tetragonal transition under pressure takes place concomitantly with the onset of superconductivity. The electronic structure of ${\mathrm{La}}_{4}{\mathrm{Ni}}_{3}{\mathrm{O}}_{10}$ can be understood using a molecular trimer basis wherein $n$ molecular subbands arise as the ${d}_{{z}^{2}}$ orbitals hybridize strongly along the $c$ axis within the trilayer. The magnetic tendencies indicate that the ground state at ambient pressure is formed by nonmagnetic inner planes and stripe-ordered outer planes that are antiferromagnetically coupled along the $c$ axis, resulting in an unusual $\ensuremath{\uparrow}$, 0, $\ensuremath{\downarrow}$ stacking that is consistent with the spin density wave model previously suggested by neutron diffraction. Such a state is destabilized at the pressure where superconductivity arises. Despite the presence of ${d}_{{z}^{2}}$ states at the Fermi level, the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ orbitals also play a key role in the electronic structure of ${\mathrm{La}}_{4}{\mathrm{Ni}}_{3}{\mathrm{O}}_{10}$. This active role of the ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ states in the low-energy physics of the trilayer RP nickelate, together with the distinct electronic behavior of the inner and outer planes, resembles the physics of multilayer cuprates.