162 research outputs found
Phase diagrams of correlated electrons: systematic corrections to the mean field theory
Perturbative corrections to the mean field theory for particle-hole
instabilities of interacting electron systems are computed within a scheme
which is equivalent to the recently developed variational approach to the
Kohn-Luttinger superconductivity. This enables an unbiased comparison of
particle-particle and particle-hole instabilities within the same approximation
scheme. A spin-rotation invariant formulation for the particle-hole
instabilities in the triplet channel is developed. The method is applied to the
phase diagram of the t-t' Hubbard model on the square lattice. At the Van Hove
density, antiferromagnetic and d-wave Pomeranchuk phases are found to be stable
close to half filling. However, the latter phase is confined to an extremely
narrow interval of densities and away from the singular filling, d-wave
superconducting instability dominates
Chiral d+is superconducting state in the two dimensional t-t' Hubbard model
Applying the recently developed variational approach to Kohn-Luttinger
superconductivity to the t-t' Hubbard model in two dimensions, we have found,
for sizeable next-nearest neighbor hopping, an electron density controlled
quantum phase transition between a d-wave superconducting state close to half
filling and an s-wave superconductor at lower electron density. The transition
occurs via an intermediate time reversal breaking d+is superconducting phase,
which is characterized by nonvanishing chirality and density-current
correlation. Our results suggest the possibility of a bulk time reversal
symmetry breaking state in overdoped cuprates
The effect of soil conditioner on the spatial variability of soil environment
ArticleThe aim of the study was to assess and evaluate the effect of soil conditioner on the
spatial variability of soil environment. Activator PRP-SOL conditioning soil properties was
selected as a field of study. Assessment of soil environment was done through the evaluation of
selected soil properties, namely, tensile resistance of the soil and soil infiltration ability. Two
dose of PRP-SOL application was done twice in year 2015 (Autumn and Spring) and once in
2016 (Spring) with application rates 150 kg ha-1
and 140 kg ha-1
, respectively. The area was
divided into blocks where stimulators were applied and none treated as a control. The evaluation
of recorded values showed that treatability and tillage itself was significantly better on the area
which was treated by application of PRP-SOL activators. In addition, tensile resistance was
decreased by 5.71% in comparison with non-treated area of experimental field. Since the
infiltration ability is among the very important soil properties which have an effect on soil
moisture regime as well as surface runoff and therefore soil erosion. The evaluation of recorded
values has revealed the effect of treatment by PRP-SOL activators on soil infiltration ability and
therefore it results in increases infiltration of precipitation as well. Overall increase of infiltration
was recorded at value 2 mm h
-1
. It can be concluded that application of soil activators may
increase the soil conditions and therefore not only conserve soil fertility but even increase it from
the long term perspective
Kohn-Luttinger instability of the t-t' Hubbard model in two dimensions: variational approach
An effective Hamiltonian for the Kohn-Luttinger superconductor is constructed
and solved in the BCS approximation. The method is applied to the t-t' Hubbard
model in two dimensions with the following results: (i) The superconducting
phase diagram at half filling is shown to provide a weak-coupling analog of the
recently proposed spin liquid state in the J_1-J_2 Heisenberg model. (ii) In
the parameter region relevant for the cuprates we have found a nontrivial
energy dependence of the gap function in the dominant d-wave pairing sector.
The hot spot effect in the angular dependence of the superconducting gap is
shown to be quite weak
Bond formation at polycarbonate | X interfaces (X = AlO, TiO, TiAlO) studied by theory and experiments
Interfacial bond formation during sputter deposition of metal oxide thin
films onto polycarbonate (PC) is investigated by ab initio molecular dynamics
simulations and X-ray photoelectron spectroscopy (XPS) analysis of PC | X
interfaces (X = AlO, TiO, TiAlO). Generally, the predicted bond
formation is consistent with the experimental data. For all three interfaces,
the majority of bonds identified by XPS are (C-O)-metal bonds, whereas C-metal
bonds are the minority. Compared to the PC | AlO interface, the PC |
TiO and PC | TiAlO interfaces exhibit a reduction in the measured
interfacial bond density by ~ 75 and ~ 65%, respectively. Multiplying the
predicted bond strength with the corresponding experimentally determined
interfacial bond density shows that AlO exhibits the strongest
interface with PC, while TiO and TiAlO exhibit ~ 70 and ~ 60% weaker
interfaces, respectively. This can be understood by considering the complex
interplay between the metal oxide composition, the bond strength as well as the
population of bonds that are formed across the interface
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