Turning a nickelate Fermi surface into a cuprate-like one through heterostructuring

异质结构：通向镍酸盐超导体电子掺杂的途径

Heterostructuring as Gateway to Electron Doping of Nickelate Superconductors

研究镍酸盐超导体电子掺杂难题，通过第一性原理计算，提出将宽带隙绝缘层插入特定镍酸盐的方法，可实现电子掺杂，使La₂NiO₄:La₂AlO₄处于超导最佳区域，Tc超50K，该方法也适用于La₃Ni₂O₇。

Epitaxial strain modulated electronic properties of interface controlled nickelate superlattice

Perovskite nickelate heterostructure consisting of single unit cell of EuNiO$_3$ and LaNiO$_3$ have been grown on a set of single crystalline substrates by pulsed laser interval deposition to investigate the effect of epitaxial strain on electronic and magnetic properties at the extreme interface limit. Despite the variation of substrate in-plane lattice constants and lattice symmetry, the structural response to heterostructuring is primarily controlled by the presence of EuNiO$_3$ layer. In sharp contrast to bulk LaNiO$_3$ or EuNiO$_3$, the superlattices grown under tensile strains exhibit me…

Dynamical Mean Field Theory of Nickelate Superlattices

Dynamical mean field methods are used to calculate the phase diagram, many-body density of states, relative orbital occupancy and Fermi surface shape for a realistic model of $LaNiO_3$-based superlattices. The model is derived from density functional band calculations and includes oxygen orbitals. The combination of the on-site Hunds interaction and charge-transfer between the transition metal and the oxygen orbitals is found to reduce the orbital polarization far below the levels predicted either by band structure calculations or by many-body analyses of Hubbard-type models which do not expli…

Physics of ultrathin films and heterostructures of rare earth nickelates

The electronic structure of transition metal oxides featuring correlated electrons can be rationalized within the Zaanen-Sawatzky-Allen framework. Following a brief description of the present paradigms of electronic behavior, we focus on the physics of rare earth nickelates as an archetype of complexity emerging within the charge transfer regime. The intriguing prospect of realizing the physics of high $T_c$ cuprates through heterostructuring resulted in a massive endeavor to epitaxially stabilize these materials in ultra-thin form. A plethora of new phenomena unfolded in such artificial struc…

Orbital engineering in nickelate heterostructures driven by anisotropic oxygen hybridization rather than orbital energy levels

Resonant inelastic x-ray scattering is used to investigate the electronic origin of orbital polarization in nickelate heterostructures taking $\mathrm{LaTiO_3-LaNiO_3-3x(LaAlO_3)}$, a system with exceptionally large polarization, as a model system. We find that heterostructuring generates only minor changes in the Ni $3d$ orbital energy levels, contradicting the often-invoked picture in which changes in orbital energy levels generate orbital polarization. Instead, O $K$-edge x-ray absorption spectroscopy demonstrates that orbital polarization is caused by an anisotropic reconstruction of the o…

Probing electronic and magnetic transitions of short periodic nickelate superlattices using synchrotron x-ray

Transition metal based oxide heterostructures exhibit diverse emergent phenomena e.g. two dimensional electron gas, superconductivity, non-collinear magnetic phase, ferroelectricity, polar vortices, topological Hall effect etc., which are absent in the constituent bulk oxides. The microscopic understandings of these properties in such nanometer thick materials are extremely challenging. Synchrotron x-ray based techniques such as x-ray diffraction, x-ray absorption spectroscopy (XAS), resonant x-ray scattering (RXS), resonant inelastic x-ray scattering (RIXS), x-ray photoemission spectroscopy, …