Surfaces and interfaces of infinite-layer nickelates studied by dynamical mean-field theory

Infinite-layer nickelate superconductors are typically synthesized as thin films and thus include, besides the more bulk-like inner layers, distinct surface and interface layers in contact with the vacuum and substrate, respectively. Here, we employ density-functional theory and dynamical mean-field theory to investigate how electronic correlations influence these surface and interface regions. Our results show that electronic correlations can significantly modify the electronic structure, even driving surface layers into a Mott-insulating state with a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mn>3</a:mn> <a:msup> <a:mi>d</a:mi> <a:mn>8</a:mn> </a:msup> </a:mrow> </a:math> electronic configuration. Moreover, surface termination effects induce a polar field that can shift the <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mi mathvariant="normal">Γ</b:mi> </b:math> and <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mi>A</d:mi> </d:math> pocket above the Fermi level, even for the undoped parent compound <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:msub> <e:mi>NdNiO</e:mi> <e:mn>2</e:mn> </e:msub> </e:math> . Finally, for an <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mi>n</f:mi> </f:math> -type interface, often synthesized experimentally, we find the Ti <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mrow> <g:mn>3</g:mn> <g:mi>d</g:mi> </g:mrow> </g:math> orbitals to become electron doped.