The exclusive b → + − decay is analysed in the model III version of the two Higgs doublet model. We especially studied the branching ratio and the forward-backward asymmetry of this process and investigated the sensitivity of these physical observables to the model parameters. We have found that they are highly sensitive to new physics and hence provide powerful probe of the SM.

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Cation intermixing at functional oxide interfaces remains a highly controversial area directly relevant to interface-driven nanoelectronic device properties. Here, we systematically explore the cation intermixing in epitaxial (001) oriented multiferroic bismuth ferrite (BFO) grown on a (001) lanthanum aluminate (LAO) substrate. Aberration corrected dedicated scanning transmission electron microscopy and electron energy loss spectroscopy reveal that the interface is not chemically sharp, but with an intermixing of ∼2 nm. The driving force for this process is identified as misfit-driven elastic strain. Landau-Ginzburg-Devonshire-based phenomenological theory was combined with the Sheldon and Shenoy formula in order to understand the influence of boundary conditions and depolarizing fields arising from misfit strain between the LAO substrate and BFO film. The theory predicts the presence of a strong potential gradient at the interface, which decays on moving into the bulk of the film. This potential gradient is significant enough to drive the cation migration across the interface, thereby mitigating the misfit strain. Our results offer new insights on how chemical roughening at oxide interfaces can be effective in stabilizing the structural integrity of the interface without the need for misfit dislocations. These findings offer a general formalism for understanding cation intermixing at highly strained oxide interfaces that are used in nanoelectronic devices.

We present a theoretical description of the influence of misfit strain on mobile defects dynamics in thin strained ferroelectric films. Self-consistent solutions obtained by coupling the Poisson's equation for electric potential with continuity equations for mobile donor and electron concentrations and time-dependent Landau-Ginzburg-Devonshire equations reveal that the Vegard mechanism (chemical pressure) leads to the redistribution of both charged and electro-neutral defects in order to decrease the effective stress in the film. Internal electric fields, both built-in and depolarization ones, lead to a strong accumulation of screening space charges (charged defects and electrons) near the film interfaces. Importantly, the corresponding screening length is governed by the misfit strain and Vegard coefficient.Mobile defects dynamics, kinetics of polarization and electric current reversal are defined by the complex interplay between the donor, electron and phonon relaxation times, misfit strain, finite size effect and Vegard stresses.

We report a study on multiferroic bismuth ferrite ͑BiFeO 3 , BFO͒-ferromagnetic lanthanum strontium manganese oxide ͑La 0.7 Sr 0.3 MnO 3 , LSMO͒ epitaxial interfaces by scanning transmission electron microscopy-energy dispersive spectroscopy ͑STEM-EDS͒ and energy-filtered transmission electron microscopy ͑EFTEM͒. Epitaxial ͑001͒ oriented LSMO/BFO heterostructures were fabricated on a ͑001͒ strontium titanate ͑SrTiO 3 , STO͒ substrate using pulsed laser deposition ͑PLD͒. Different cooling conditions to room temperature ͑rapid or slow͒ were used to investigate the effect of fabrication conditions on the structural quality of the interfaces. The combined analysis of bright field transmission electron microscopy imaging, STEM-EDS and EFTEM data reveals that the LSMO-BFO heterostructure interface is free from any defects but the phases are chemically interdiffused over a length scale of ϳ4 nm.

BaTiO 3 (BTO) typically demonstrates a strong ntype character with absorption only in the ultraviolet (λ ≤ 390 nm) region. Extending the applications of BTO to a range of fields necessitates a thorough insight into how to tune its carrier concentration and extend the optical response. Despite significant progress, simultaneously inducing visible-light absorption with a controlled carrier concentration via doping remains challenging. In this work, a p-type BTO with visible-light (λ ≤ 600 nm) absorption is realized via iridium (Ir) doping. Detailed analysis using advanced spectroscopy/microscopy tools revealed mechanistic insights into the n-to p-type transition. The computational electronic structure analysis further corroborated this observation. This complementary data helped establish a correlation between the occupancy and the position of the dopant in the band gap with the carrier concentration. A decrease in the Ti 3+ donor-level concentration and the mutually correlated oxygen vacancies upon Ir doping is attributed to the p-type behavior. Due to the formation of Ir 3+ /Ir 4+ in-gap energy levels within the forbidden region, the optical transition can be elicited from or to such levels, resulting in visible-light absorption. This newly developed Ir-doped BTO is a promising semiconductor with imminent applications in solar fuel generation and optoelectronics.

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Crystal structure change with an applied electric field was investigated by Raman spectroscopy and X-ray diffraction (XRD) for the 1 m-thick (100)/(001) one-axis oriented tetragonal Pb(Zr 0.3 Ti 0.7 )O 3 films prepared on Pt-covered (100) Si substrates by chemical solution deposition technique. As-deposited films were under the strained condition in good agreement with the estimation from the thermal strain applied under the cooling process after the deposition from the Curie temperature to the room temperature. This strain was ascertained to be relaxed by an applied electric field in accompanying with the dramatic increase of the volume fraction of (001) orientation. These results demonstrate the importance of the crystal structure measurement not only as-deposited films, but also after applied electric field, such as after poling.