Bulk NdNiO3 and thin films grown along the pseudocubic (001)pc axis display a 1st order metal to insulator transition (MIT) together with a Néel transition at T = 200 K. Here, we show that for NdNiO3 ...films deposited on (111)pc NdGaO3, the MIT occurs at T = 335 K and the Néel transition at T = 230 K. By comparing transport and magnetic properties of layers grown on substrates with different symmetries and lattice parameters, we demonstrate a particularly large tuning when the epitaxy is realized on (111)pc surfaces. We attribute this effect to the specific lattice matching conditions imposed along this direction when using orthorhombic substrates.
Abstract
Phonon polaritons are promising for infrared applications due to a strong light-matter coupling and subwavelength energy confinement they offer. Yet, the spectral narrowness of the phonon ...bands and difficulty to tune the phonon polariton properties hinder further progress in this field. SrTiO
3
– a prototype perovskite oxide - has recently attracted attention due to two prominent far-infrared phonon polaritons bands, albeit without any tuning reported so far. Here we show, using cryogenic infrared near-field microscopy, that long-propagating surface phonon polaritons are present both in bare SrTiO
3
and in LaAlO
3
/SrTiO
3
heterostructures hosting a two-dimensional electron gas. The presence of the two-dimensional electron gas increases dramatically the thermal variation of the upper limit of the surface phonon polariton band due to temperature dependent polaronic screening of the surface charge carriers. Furthermore, we demonstrate a tunability of the upper surface phonon polariton frequency in LaAlO
3
/SrTiO
3
via electrostatic gating. Our results suggest that oxide interfaces are a new platform bridging unconventional electronics and long-wavelength nanophotonics.
We report a detailed analysis of magneto-transport properties of top- and back-gated LaAlO3/SrTiO3 heterostructures. Efficient modulation in magneto-resistance, carrier density, and mobility of the ...two-dimensional electron liquid present at the interface is achieved by sweeping top and back gate voltages. Analyzing those changes with respect to the carrier density tuning, we observe that the back gate strongly modifies the electron mobility while the top gate mainly varies the carrier density. The evolution of the spin-orbit interaction is also followed as a function of top and back gating.
Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy, we report electronic structure measurements of (111)-oriented LaNiO3/LaMnO3 superlattices ...and LaNiO3 epitaxial films. For thin films, we observe a 3D Fermi surface with an electron pocket at the Brillouin zone center and hole pockets at the zone vertices. Superlattices with thick nickelate layers present a similar electronic structure. However, as the thickness of the LaNiO3 is reduced, the superlattices become insulating. These heterostructures do not show a marked redistribution of spectral weight in momentum space but exhibit a pseudogap of ≈50 meV.
Numerous solid-state properties depend on the crystal structure. Recently, the idea of searching for novel properties or novel functionalities at artificial interfaces – where a breaking of inversion ...symmetry and a change in the atomic environment occur – has been developing rapidly and has led to a large new field of research. In this short paper, we will summarize the properties of the 2-d electron gas found at the interface between the two band insulators LaAlO
3
and SrTiO
3
, discuss briefly the recent observations of electron gases at oxide surfaces and examine the possible similarities and differences between these exciting systems.
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