56 research outputs found
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 NdNiO Thin Films
Transport measurements on thin films of NdNiO 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 is decreased below the nominal transition temperature, transport
becomes increasily non-Ohmic, with a model of Landau-Zener breakdown becoming
most suited for describing characteristics as the temperature approaches
2~K.Comment: 18 pages, 6 figures, accepted for publication in PR
Ionic liquid gating of SrTiO 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 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
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