Response of the lattice across the filling-controlled Mott metal-insulator transition of a rare earth titanate

The lattice response of a prototype Mott insulator, SmTiO3, to hole doping is investigated with atomic-scale spatial resolution. SmTiO3 films are doped with Sr on the Sm site with concentrations that span the insulating and metallic sides of the filling-controlled Mott metal-insulator transition (MIT). The GdFeO3-type distortions are investigated using an atomic resolution scanning transmission electron microscopy technique that can resolve small lattice distortions with picometer precision. We show that these distortions are gradually and uniformly reduced as the Sr concentration is increased without any phase separation. Significant distortions persist into the metallic state. The results present a new picture of the physics of this prototype filling-controlled MIT, which is discussed.Comment: Accepted, Phys. Rev. Let

COMPARATIVE ASSESSMENT OF THE EFFECT OF GIBBERELLIC AND SALICYLIC ACIDS ON THE GROWTH AND BIOCHEMICAL PARAMETERS OF Phaeodactylum tricornutum

The research of the effect of gibberellic (0.4 - 3.8x 10-8 mol.L-1) and salicylic (0.4 - 3.8 x 10-5 mol.L-1) acids, in a wide range of their concentrations, on the growth indicators and biochemical composition of the cumulative culture of the microalgae Phaeodactylum tricornutum was carried out. It was determined that salicylic acid in a concentration of 0.4 x 10-5 mol stimulated cell growth by 184.6%, and gibberellic acid at a concentration of 0.39 x 10-8 mol by 181%, compared to the control. The effect of gibberellic acid during the experiment was expressed in the inhibition of protein accumulation in the culture, compared with the control. The use of salicylic acid led to a greater accumulation of protein in the culture than when using gibberellic acid. It was shown that salicylic acid had a positive effect on the accumulation of carbohydrates on day 9 and gibberellic acid on day 14 of culture. Gibberellic acid had no effect on the accumulation of lipids in the culture of microalgae. Under the action of salicylic acid for 14 days of cultivation, the lipid content increased by 18.5%, compared with the control. There were no quantitative differences in the content of chlorophyll when using two phytohormones. In this study, the optimal concentrations of gibberellic and salicylic acids for linear growth rate and the highest production of protein and carbohydrates for Phaeodactylum tricornutum were determined. Position, depending on the stage of microalgae growth, is noted

Tuning bad metal and non-Fermi liquid behavior in a Mott material: rare earth nickelate thin films

Resistances that exceed the Mott-Ioffe-Regel limit, known as bad metal behavior, and non-Fermi liquid behavior are ubiquitous features of the normal state of many strongly correlated materials. Here we establish the conditions that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a prototype, bandwidth-controlled metal-insulator transition. We show that resistance saturation is determined by the magnitude of the Ni eg orbital splitting, which can be tuned by strain in epitaxial films, causing the appearance of bad metal behavior under certain conditions. The results shed light on the nature of a crossover to non-Fermi liquid metal phase and provide a predictive criterion for strong localization. They elucidate a seemingly complex phase behavior as a function of film strain and confinement and provide guidelines for orbital engineering and novel devices.Comment: Manuscript text, 5 figures and supplemen

Nanostructure Investigations of Nonlinear Differential Conductance in NdNiO3_3 Thin Films

Transport measurements on thin films of NdNiO$_3$ reveal a crossover to a regime of pronounced nonlinear conduction below the well-known metal-insulator transition temperature. The evolution of the transport properties at temperatures well below this transition appears consistent with a gradual formation of a gap in the hole-like Fermi surface of this strongly correlated system. As $T$ is decreased below the nominal transition temperature, transport becomes increasily non-Ohmic, with a model of Landau-Zener breakdown becoming most suited for describing $I(V)$ characteristics as the temperature approaches 2~K.Comment: 18 pages, 6 figures, accepted for publication in PR

Ionic liquid gating of SrTiO3_3 lamellas fabricated with a focused ion beam

In this work, we combine two previously-incompatible techniques for defining electronic devices: shaping three-dimensional crystals by focused ion beam (FIB), and two-dimensional electrostatic accumulation of charge carriers. The principal challenge for this integration is nanometer-scale surface damage inherent to any FIB-based fabrication. We address this by using a sacrificial protective layer to preserve a selected pristine surface. The test case presented here is accumulation of 2D carriers by ionic liquid gating at the surface of a micron-scale SrTiO$_3$ lamella. Preservation of surface quality is reflected in superconductivity of the accumulated carriers. This technique opens new avenues for realizing electrostatic charge tuning in materials that are not available as large or exfoliatable single crystals, and for patterning the geometry of the accumulated carriers