arXiv subjects

I. A. Kruglov

Publications and source records attributed to I. A. Kruglov.

4 recordsLinked to original sources

arXiv2025

Ionic Disorder-Mediated Exfoliation and Optical Birefringence in a Non-van der Waals Oxide

The landscape of two-dimensional photonics has been dominated by van der Waals (vdW) materials. Expanding this library to include non-vdW layered systems promises enhanced environmental robustness and access to novel functionalities, such as strong ionic conductivity, yet their exfoliation remains challenging. Here, we establish Na2Zn2TeO6 (NZTO), a P2-type superionic conductor, as an exfoliable non-vdW optical material. We demonstrate that the highly disordered, mobile Na+ interlayer inherently facilitates mechanical cleavage down to few-nanometer thicknesses (about 4 nm). Optical interrogation via spectroscopic ellipsometry reveals NZTO as a wide-bandgap dielectric with pronounced optical birefringence (Delta_n about 0.25) across the visible and near-infrared spectrum. The lattice dynamics, probed by temperature-resolved Raman spectroscopy, underscore the rigidity of the [Zn2TeO6]2- framework, which remains largely decoupled from the high ionic mobility. These results identify NZTO as a compelling platform for robust, anisotropic dielectric photonics, simultaneously opening a pathway toward the convergence of ionic transport and optical control - an emerging paradigm we term iono-photonics.

physics.optics↗

arXiv2023

MXene Fe2C as a promising candidate for the 2D XY ferromagnet

Monolayer Fe$_2$C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this work we consider electronic and magnetic properties of MXene Fe$_2$C within the DFT+DMFT approach. We establish the existence of local magnetic moments $μ=3.2μ_B$ in this compound, characterized by sufficiently long lifetime of $τ\sim 350$ fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. We obtain the strongest exchange interaction $11$ meV between next nearest neighboring Fe atoms above (and below) the carbon plane, and the subleading interaction $6$ meV between the next to next nearest neighboring atoms across the carbon plane. The resulting dependence of the Berzinskii-Kosterlitz-Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained. The BKT temperature for the pristine Fe$_2$C is $T_{\rm BKT}\simeq 290$ K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.

cond-mat.str-el↗

arXiv2023

Hexagonal boron nitride nanophotonics

A global trend to miniaturization and multiwavelength performance of nanophotonic devices drives research on novel phenomena, such as bound states in the continuum and Mietronics, as well as the survey for high-refractive index and strongly anisotropic materials and metasurfaces. Hexagonal boron nitride (hBN) is one of promising materials for the future nanophotonics owing to its inherent anisotropy and prospects of high-quality monocrystals growth with atomically flat surface. Here, we present highly accurate optical constants of hBN in the broad wavelength range of 250-1700 nm combining the imaging ellipsometry measurements scanning near-field optical microscopy and first-principle quantum mechanical computations. hBN's high refractive index, up to 2.75 in ultraviolet (UV) and visible range, broadband birefringence of 0.7, and negligible optical losses make it an outstanding material for UV and visible range photonics. Based on our measurement results, we propose and design novel optical elements: handedness-preserving mirrors and subwavelength waveguides with dimensions of 40 nm operating in the visible and UV range, respectively. Remarkably, our results offer unique opportunity to bridge the size-gap between photonics and electronics.

physics.optics↗

arXiv2021

Giant optical anisotropy in transition metal dichalcogenides for next-generation photonics

Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy was recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Walls interaction. To do this, we carried out a correlative far- and near-field characterization validated by first-principle calculations that reveals an unprecedented birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this outstanding anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics.

physics.app-ph↗