arXiv subjects

Ilya Popov

Publications and source records attributed to Ilya Popov.

4 recordsLinked to original sources

arXiv2026

Three-dimensional Moir\'e crystallography

Moir\'e materials, typically confined to stacking atomically thin, two - dimensional (2D) layers such as graphene or transition metal dichalcogenides, have transformed our understanding of strongly correlated and topological quantum phenomena. The lattice mismatch and relative twist angle between 2D layers have shown to result in Moir\'e patterns associated with widely tunable electronic properties, ranging from Mott and Chern insulators to semi- and super-conductors. Extended to three-dimensional (3D) structures, Moir\'e materials unlock an entirely new crystallographic space defined by the elements of the 3D rotation group and translational symmetry of the constituent lattices. 3D Moir\'e crystals exhibit fascinating novel properties, often not found in the individual components, yet the general construction principles of 3D Moir\'e crystals remain largely unknown. Here we establish fundamental mathematical principles of 3D Moir\'e crystallography and propose a general method of 3D Moir\'e crystal construction using Clifford algebras over the field of rational numbers. We illustrate several examples of 3D Moir\'e structures representing realistic chemical frameworks and highlight their potential applications in condensed matter physics and solid-state chemistry.

cond-mat.mtrl-sci↗

arXiv2025

Multiplet structure of chromium(III) dopants in wide band gap materials

Transition metal doping is commonly used for altering the properties of solid-state materials to suit applications in science and technology. Partially filled $d$-shells of transition metal atoms lead to electronic states with diverse spatial and spin symmetries. Chromium(III) cations have shown great potential for designing laser materials and, more recently, for developing spin qubits in quantum applications. They also represent an intriguing class of chemical systems with strongly correlated multi-reference excited states, due to the $d^3$ electron configuration. These states are difficult to describe accurately using single-reference quantum chemical methods such as density functional theory (DFT), the most commonly used method to study the electronic structures of solid-state systems. Recently, the periodic effective Hamiltonian of crystal field (pEHCF) method has been shown to overcome some limitations arising in the calculations of excited $d$-states. In this work, we assess the suitability of DFT and pEHCF to calculate the electronic structure and $d$-$d$ excitations of chromium(III) dopants in wide band gap host materials. The results will aid computational development of novel transition metal-doped materials and provide a deeper understanding of the complex nature of transition metal dopants in solids.

cond-mat.mtrl-sci↗

arXiv2025

Timing the Escape of a Caged Electron

Charge transfer is fundamentally dependent on the overlap of the orbitals comprising the transport pathway. This has key implications for molecular, nanoscale, and quantum technologies, for which delocalization (and decoherence) rates are essential figures of merit. Here, we apply the core hole clock technique - an energy-domain variant of ultrafast spectroscopy - to probe the delocalization of a photoexcited electron inside a closed molecular cage, namely the Ar 2p54s1 state of Ar@C60. Despite marginal frontier orbital mixing in the ground configuration, almost 80% of the excited state density is found outside the buckyball due to the formation of a markedly diffuse hybrid orbital. Far from isolating the intracage excitation, the surrounding fullerene is instead a remarkably efficient conduit for electron transfer: we measure characteristic delocalization times of 6.6 $\pm$ 0.3 fs and $\lesssim$ 500 attoseconds, respectively, for a 3D Ar@C60 film and a 2D monolayer on Ag(111).

physics.chem-ph↗

arXiv2024

A Universal Knowledge Model and Cognitive Architecture for Prototyping AGI

The article identified 42 cognitive architectures for creating general artificial intelligence (AGI) and proposed a set of interrelated functional blocks that an agent approaching AGI in its capabilities should possess. Since the required set of blocks is not found in any of the existing architectures, the article proposes a new cognitive architecture for intelligent systems approaching AGI in their capabilities. As one of the key solutions within the framework of the architecture, a universal method of knowledge representation is proposed, which allows combining various non-formalized, partially and fully formalized methods of knowledge representation in a single knowledge base, such as texts in natural languages, images, audio and video recordings, graphs, algorithms, databases, neural networks, knowledge graphs, ontologies, frames, essence-property-relation models, production systems, predicate calculus models, conceptual models, and others. To combine and structure various fragments of knowledge, archigraph models are used, constructed as a development of annotated metagraphs. As components, the cognitive architecture being developed includes machine consciousness, machine subconsciousness, blocks of interaction with the external environment, a goal management block, an emotional control system, a block of social interaction, a block of reflection, an ethics block and a worldview block, a learning block, a monitoring block, blocks of statement and solving problems, self-organization and meta learning block.

cs.AI↗