Engineered Mott ground state in a LaTiO(3+δ)/LaNiO3 heterostructure.

Yanwei Cao,P J Ryan,J.-W Kim,J Chakhalian,J.W Freeland,Xiaoran Liu,M Kareev,S Middey,D Meyers,D Choudhury

doi:10.1038/ncomms10418

Abstract

In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states.

Highlights

In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results
Some of the most remarkable physical phenomena such as high-TC superconductivity and colossal magnetoresistance, are observed in charge-transfer compounds characterized by the strong hybridization between oxygen 2p and transition metal 3d states, complex electronic configurations and small or even negative charge excitation gap DCT
The role of the lower Hubbard band is replaced by the oxygen states, which in turn implies a very asymmetric physical character for the doped holes and doped electrons, for example, correlated metal LaNiO3 (LNO)

Summary

Introduction

In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. To further corroborate these findings, the interfacial charge-transfer phenomenon was studied by measuring the core-level electronic structures of Ti and Ni with in-situ XPS (see Supplementary Fig. 3); as determined by XPS, the resulting charge states of Ni and Ti in the 2LTO/2LNO sample are in excellent agreement with those obtained by XAS at Ti L2,3- and Ni L2,3-edges.

Results

Conclusion