Electronic Properties and Superconductivity in Infinite-Layer Nickelate Composts

Abstract

In this paper, we investigate the electronic and superconducting properties in nickelate compounds of $\hbox {NiO}_2$ through perturbative density functional theory (P-DFT) and extended multi-band Bardeen–Cooper–Schrieffer (BCS) theory. We consider four different cases of study: (i) the crystalline structure composed by one layer of $\hbox {NiO}_2$, with a central single atom of Nd, Yb or Pr, which is subjected to mechanical compression and tension forces (pressure), (ii) the crystalline structure composed by two layers of $\hbox {NiO}_2$ with central atom pairs of Nd–Sr, Yb–Sr or Pr–Sr, with level doping $x=0.5$, (iii) the crystalline structure composed by three layers of $\hbox {NiO}_2$ with a setup of Nd–Nd(Sr)–Nd, Yb–Yb(Sr)–Yb or Pr–Pr(Sr)–Pr (Homogeneous and doping sample), with the level doping $x=0.3$ and $x=0.75$ and finally (iv) through multi-band theory we study the behavior in a single-layer ${\hbox {Nd}_{1-x}\hbox {Sr}_{x}\hbox {NiO}_2}$ when $x=0.5$ through gaps $\Delta _{\chi ,\mathbf{p }}$, with $\chi$ (number of band or orbitals), only with the presence of inter-band coupling $V_{\chi \chi '}$. As results, for (i), (ii) and (iii) we present the electronic measures of the electronic band structures e-DOS, and density of phonons (mechanical and/or optic) p-DOS. In (i), we show that under pressure there are a redistribution of the band structures for e-DOS and p-DOS, allowing the destruction of Van Hove near Fermi level $E_\mathrm{F}$; thus, in (ii) and (iii) we show the presence of a single flat band when the doping level is $x=0.5$, and for (iv), the inter-band coupling between orbitals plays a key role in the construction of a superconducting phase in nickelate compounds.