Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

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.

Tunable correlated-electron phases in (111) LaAlO3/SrTiO3 band insulator heterostructures

“…of LaAlO 3 on top of m − 0.5 u.c. of SrTiO 3 . The in-plane lattice parameter, perpendicular to the [111] direction, was fixed to 5.52Å, corresponding to the calculated equilibrium 3.905Å bulk SrTiO 3 cubic lattice constant.…”

“…Therefore, in atomically engineered oxide HSs new and unprecedented ground states emerge [1][2][3]. The prototypical example is (001)-oriented LaAlO 3 /SrTiO 3 HSs formed by two nonmagnetic band insulators.…”

“…The polar discontinuity at the interface is primarily considered to drive the occurrence of the 2DEG [4,11,12], but oxygen vacancies [13][14][15], cation intermixing [11,12], and even surface protonation [16,17] also yield conductive HSs. It is widely accepted that the 2DEG is confined in the SrTiO 3 and, irrespective of the SrTiO 3 thickness, electrons mainly reside at the two-dimensional (2D) d xy orbital of the interface TiO 2 plane. However, there is also some occupation of the d xy noninterface TiO 2 and the 3D d yz/zx derived bands [18][19][20][21][22][23].…”

Avoiding polar catastrophe in the growth of polarly orientated nickel perovskite thin films by reactive oxide molecular beam epitaxy

“…[7][8][9] Furthermore, LNO is widely explored as conductive electrode materials [10][11][12][13] as well as building bricks of various superlattices in pursuing all-oxide electronics and emergent physics. [14][15][16][17] Recently, it was predicted that superconductivity may hatch in the LNO-based (001) superlattices (in pseudo-cubic indices) which displayed cuprate-like fermi surface with a planar x 2 − y 2 orbital order. 18,19 Moreover, topological phases which have only been discovered in oxygen-free compounds until now, were theoretically shown to exist in LNO-based (111) superlattices with buckled honeycomb lattices reminiscent of graphene.…”

“…High-quality LNO films were achieved via sputtering 8,9 and pulsed laser deposition (PLD). 15,17,25,26 Compared to these two techniques, the state-of-the-art reactive oxide molecular beam epitaxy (OMBE) is a low-energy deposition method, and can control the growth at atomic scale which can essentially allow the fabrication of high-quality thin films and superlattices with sharp interfaces. [27][28][29][30][31] Moreover, films grown by OMBE have clean and natural "cleaved" surfaces which can further be investigated by in situ combined powerful probes like angle-resolved photoemission spectroscopy (ARPES) 7,32 and scanning tunneling microscopy (STM) that could lay the foundation for future electronic structure studies.…”