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Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.

The effect of randomly distributed Ca dopants within the BaTiO3 lattice was investigated using first principle calculations. We examined electronic properties to understand how different orbitals contribute to the conduction and valence bands in doped materials. Our findings indicate that the valence band is primarily composed of Ti-3d and O-2p orbital states, while the conduction band is influenced by the collective contributions of Ba-4d, Ti-3d, and Ca-3d orbital states. Additionally, our results demonstrate a reduction in the bandgap due to Ca doping, with the extent of variation depending on the substituted sites of the Ca atoms. Furthermore, we investigated modifications in optical properties such as absorption, conductivity, dielectric function, refractive index, extinction coefficient, loss function, and reflectivity in the energy range from 0 to 40 eV. The findings reveal the stability of these characteristics in the infrared and visible light regions, and they also depend on the site substitution of Ca cations within the BaTiO3 lattice. We expected that our findings would deepen the understanding of the mechanism and site effect of Ca dopant on the properties of BaTiO3 materials, thereby contributing to the development of lead-free ferroelectric materials with enhanced properties for multifunctional applications. [ABSTRACT FROM AUTHOR]

Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures. [ABSTRACT FROM AUTHOR]

The strongly enhanced room temperature ferromagnetism in Bi0.5Na0.5TiO3 materials was obtained via modification of YMnO3 as solid solutions. The weak ferromagnetism in pure Bi0.5Na0.5TiO3 was changed to ferromagnetism and antiferromagnetic-like with increasing the concentration of YMnO3 addition. The maxima magnetic moment was estimated at around 28.4 memu/g for 9 mol.% YMnO3-modified Bi0.5Na0.5TiO3 as a solid solution. The reduction of the optical bandgap energy from 3.18 eV to 2.01 eV was obtained via increasing YMnO3 addition into host Bi0.5Na0.5TiO3 crystal as solid solutions with amounts up to 9 mol.%. We suggested that the observation in the reduction of optical bandgap energy and great enhancement of the magnetic moment in YMnO3-modified Bi0.5Na0.5TiO3 compounds were strongly related to the random distribution of Y and Mn cations into the host lattice of Bi0.5Na0.5TiO3 crystals. We expected that our work will provide a simple way to integrate room temperature ferromagnetism into currently developed green ferroelectric materials. [ABSTRACT FROM AUTHOR]

Er½Na½TiO3–Bi½Na½TiO3 solid solutions were prepared by a sol–gel technique. The complex distortion of the rhombohedral structure of host Bi½Na½TiO3 compounds was obtained caused by the addition of the solid solution of Er½Na½TiO3 into the host Bi½Na½TiO3 matrix. The random incorporation of Er3+ cations into the host crystal of the Bi½Na½TiO3 material resulted in reducing its optical band gap from 3.04 to 2.79 eV by increasing the Er½Na½TiO3 amount. The strong green emission at 550 nm was obtained at room temperature and is related to the emission of Er3+ cations from 4S3/2 to 4I15/2 levels. The observation of strong photoemissions at room temperature of Er½Na½TiO3-Bi½Na½TiO3 binary system promises to create the next generation of smart electronic devices. [ABSTRACT FROM AUTHOR]

Vanadium ditelluride (VTe2) has been intensively explored to understand the charge density wave (CDW) phase and its connection to magnetic properties. Here, we conduct a systematic study to understand the fine structure of CDW via scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations. STM topograph at 79 K shows that a CDW phase in VTe2 has a stripe modulation with 3 × 1 periodicity, following the double zigzag chain of distorted Te lattices. Interestingly, the 3 × 1 CDW modulation undergoes contrast inversion between filled and empty state topographs. Atomistic features and contrast changes of CDW observed in STM are clearly reproduced in our DFT simulation images. Charge distribution calculation indicates that the spatial extension and density of Te 5p orbitals have strong variations with filled and empty states, explaining the fine structure of 3 × 1 CDW in VTe2. Our finding provides an inspiring insight to further research on the less explored electronic structure of VTe2. [ABSTRACT FROM AUTHOR]

A new solid solution system of binary (1-x)Bi1/2Na1/2TiO3 + xNd1/2Na1/2TiO3 compound was well synthesized by a chemical method. The structural studies by X-ray diffraction and Raman scattering techniques provided strong evidence for the complex incorporation of Nd3+ cations into the host Bi1/2Na1/2TiO3 crystal during the formation of solid solutions. The random substitution of Nd3+ cations at both A- and B-sites of the host Bi1/2Na1/2TiO3 crystal resulted in reducing the optical bandgap from 3.05 to 2.94 eV. The strong photoemission intensity in the near-infrared region, around 883–915 nm, was obtained at room temperature, which was related to electron transitions from 4F3/2 to 4I9/2 levels of Nd3+ cations. The observation in near-infrared photoemission of the new binary Nd1/2Na1/2TiO3-modified Bi1/2Na1/2TiO3 materials exhibited a new method successfully applied for the integration of photoluminescence in lead-free ferroelectric materials for further smart electronic device applications. [ABSTRACT FROM AUTHOR]