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Electronic structure of higher-order layered palladates: La$_{n+1}$Pd$_{n}$O$_{2n+1}$ $(n = 4-7)$

Alexander K. Gavrilov, Lidia C. Santander, Antia S. Botana

Abstract

The square-planar layered nickelates R$_{n+1}$Ni$_n$O$_{2n+2}$ (R= Nd, $n=4-7$) have been recently shown to be superconducting without the need for chemical doping or pressure. Here, we examine the electronic structure of the analog higher-order square-planar palladates --that have not yet been synthesized-- via \textit{ab initio} calculations. These layered palladates exhibit larger bandwidths, an increased $p-d$ hybridization, and less interference from R-$d$ bands at the Fermi level. These characteristics make them closer cuprate analogs and promising candidates to pursue in the context of unconventional superconductivity.

Electronic structure of higher-order layered palladates: La$_{n+1}$Pd$_{n}$O$_{2n+1}$ $(n = 4-7)$

Abstract

The square-planar layered nickelates RNiO (R= Nd, ) have been recently shown to be superconducting without the need for chemical doping or pressure. Here, we examine the electronic structure of the analog higher-order square-planar palladates --that have not yet been synthesized-- via \textit{ab initio} calculations. These layered palladates exhibit larger bandwidths, an increased hybridization, and less interference from R- bands at the Fermi level. These characteristics make them closer cuprate analogs and promising candidates to pursue in the context of unconventional superconductivity.

Paper Structure

This paper contains 6 sections, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Methodology
  3. Structural Properties
  4. Non-magnetic Electronic Structure
  5. Conclusions
  6. Acknowledgments

Figures (4)

  • Figure 1: Crystal structures of the square-planar layered palladates with $n$ representing the number of PdO$_2$ layers along the $c$ axis. Also labeled is the naming convention for inner(i), middle(m), and outer(o) layers for each of the structures.
  • Figure 2: Comparison of the band structures with orbital character highlighted for the square-planar nickelates (top row) and palladates (bottom row.) Each column corresponds to the same number of layers in the materials, starting with $n = 4$ up to $n = 7$ layers. The right panels show the corresponding Fermi surface cuts at $k_z$=0.
  • Figure 3: Comparison of the atom-resolved density of states for the square-planar nickelates (left column) and palladates (right column). Each row corresponds to the same number of layers in the corresponding materials analyzed, starting with $n = 4$ up to $n = 7$.
  • Figure 4: Top panel. Layer-resolved interlayer hoppings and charge transfer energies for the square planar palladates (in eV). The charge transfer energies are labeled in red, while the interlayer hoppings are labeled in blue. Bottom panel. Comparison of the average charge transfer energies ($\Delta$) of the square-planar nickelates (green dots) and analog palladates (blue dots). The charge-transfer energy linearly increases with the number of layers in both the palladates and the nickelates. We use a maximum $\Delta$ value for cuprates of 2.6 eV, as calculated in Ref. Weber2012-hh.