Condensed Matter Research Articles

Entanglement and Mutual Information in Molecules: Comparing Localized and Delocalized Orbitals.

The use of the mutual information (MI) as a measure of the entanglement in quantum systems has gained a consensus in recent years, even if there is an ongoing effort to distinguish the classical and quantum contributions contained therein. This quantity has been first introduced in condensed matter physics, in particular, in studies based on the density matrix renormalization group method. This method has been successfully adapted to quantum chemistry problems, opening the way to compute MI also in molecular systems. A key aspect of this quantity is its dependence on the one-electron (orbital) basis set, even for wave functions that are invariant under unitary transformation of the orbitals. In this work, we investigate the role of the orbital basis set (delocalized or localized, following different strategies) for wave functions expressed as linear combinations of Slater determinants and we give the analytic expression for the MI for a few special cases. This study aims to improve the knowledge of the relationship between the characteristics of the chemical bond (considering a few paradigmatic molecules, H2, F2, N2, and short linear polyenes) and the properties of interest in the field of quantum information theory.

Jahn-Teller Effect on CF3I Photodissociation Dynamics.

The Jahn-Teller (JT) effect, as a spontaneous symmetry-breaking mechanism arising from the coupling between electronic and nuclear degrees of freedom, is a widespread phenomenon in molecular and condensed matter systems. Here, we investigate the influence of the JT effect on the photodissociation dynamics of CF3I molecules. Based on ab initio calculation, we obtain the three-dimensional potential energy surfaces for 3Q0+ and 1Q1 states and establish a diabatic Hamiltonian model to study the wavepacket dynamics in the CF3I photodissociation process. Using the wave function of the final state after dissociation, we calculate the rotational density matrix of the CF3 fragment and analyze its rotational excitation under the JT effect, as well as its partial coherence property and selection rules. Our work paves the way to the experimental observation and quantification of the JT effect in molecular dissociation dynamics beyond the classical ball-and-stick model.

Colossal magnetoresistance from spin-polarized polarons in an Ising system

Recent experiments suggest a new paradigm toward novel colossal magnetoresistance (CMR) in a family of materials EuM 2 X 2 (M = Cd, In, Zn; X = P, As), distinct from the traditional avenues involving Kondo–Ruderman–Kittel–Kasuya–Yosida crossovers, magnetic phase transitions with structural distortions, or topological phase transitions. Here, we use angle-resolved photoemission spectroscopy and density functional theory calculations to explore their origin, particularly focusing on EuCd 2 P 2 . While the low-energy spectral weight royally tracks that of the resistivity anomaly near the temperature with maximum magnetoresistance ( T MR ) as expected from transport-spectroscopy correspondence, the spectra are completely incoherent and strongly suppressed with no hint of a Landau quasiparticle. Using systematic material and temperature dependence investigation complemented by theory, we attribute this nonquasiparticle caricature to the strong presence of entangled magnetic and lattice interactions, a characteristic enabled by the p - f mixing. Given the known presence of ferromagnetic clusters, this naturally points to the origin of CMR being the scattering of spin-polarized polarons at the boundaries of ferromagnetic clusters. These results are not only illuminating to investigate the strong correlations and topology in EuCd 2 X 2 family, but, in a broader view, exemplify how multiple cooperative interactions can give rise to extraordinary behaviors in condensed matter systems.

The Physics of Quantum 2.0: Challenges in understanding Quantum Matter

Abstract Almost a century on from the culmination of the first revolution in quantum physics, we are poised for another. Even as we engage in the creation of impactful quantum technologies, it is imperative for us to face the challenges in understanding the phenomenology of various emergent forms of quantum matter. This will involve building on decades of progress in quantum condensed matter physics, and going beyond the well-established Ginzburg-Landau-Wilson paradigm for quantum matter. I outline and discuss several outstanding challenges, including the need to explore and identify the organisational principles that can guide the development of theories, key experimental phenomenologies that continue to confound, and the formulation of methods that enable progress. These efforts will enable the prediction of new quantum materials whose properties facilitate the creation of next generation technologies.

Machine Learning With Tree Tensor Networks, CP Rank Constraints, and Tensor Dropout.

Tensor networks developed in the context of condensed matter physics try to approximate order- N tensors with a reduced number of degrees of freedom that is only polynomial in N and arranged as a network of partially contracted smaller tensors. As we have recently demonstrated in the context of quantum many-body physics, computation costs can be further substantially reduced by imposing constraints on the canonical polyadic (CP) rank of the tensors in such networks. Here, we demonstrate how tree tensor networks (TTN) with CP rank constraints and tensor dropout can be used in machine learning. The approach is found to outperform other tensor-network-based methods in Fashion-MNIST image classification. A low-rank TTN classifier with branching ratio b=4 reaches a test set accuracy of 90.3% with low computation costs. Consisting of mostly linear elements, tensor network classifiers avoid the vanishing gradient problem of deep neural networks. The CP rank constraints have additional advantages: The number of parameters can be decreased and tuned more freely to control overfitting, improve generalization properties, and reduce computation costs. They allow us to employ trees with large branching ratios, substantially improving the representation power.

Spectroscopic signatures and origin of hidden order in Ba2MgReO6

Clarifying the underlying mechanisms that govern ordering transitions in condensed matter systems is crucial for comprehending emergent properties and phenomena. While transitions are often classified as electronically driven or lattice-driven, we present a departure from this conventional picture in the case of the double perovskite Ba2MgReO6. Leveraging resonant and non-resonant elastic x-ray scattering techniques, we unveil the simultaneous ordering of structural distortions and charge quadrupoles at a critical temperature of Tq ~ 33 K. Using a variety of complementary first-principles-based computational techniques, we demonstrate that, while electronic interactions drive the ordering at Tq, it is ultimately the lattice distortions that dictate the specific ground state that emerges. Our findings highlight the crucial interplay between electronic and lattice degrees of freedom, providing a unified framework to understand and predict unconventional emergent phenomena in quantum materials.

Predictions of the interfacial free energy along the coexistence line from single-state calculations.

The calculation of the interfacial free energy between two thermodynamic phases is crucial across various fields, including materials science, chemistry, and condensed matter physics. In this study, we apply an existing thermodynamic approach, the Gibbs-Cahn integration method, to determine the interfacial free energy under different coexistence conditions, relying on data from a single-state calculation at specified pressure and temperature. This approach developed by Laird et al. [J. Chem. Phys. 131, 114110 (2009)] reduces the computational demand and enhances efficiency compared to methods that require separate measurements at each thermodynamic state. The integration scheme computes the excess interfacial free energy using unbiased constant volume, temperature, and number of particle simulations (NVT), where the two phases coexist, to provide input for the calculations. We apply this method to the Lennard-Jones and mW water models for liquid-solid interfaces, as well as the Lennard-Jones and TIP4P/2005 models for liquid-vapor interfaces. Our results demonstrate the accuracy and effectiveness of this integration route for estimating the interfacial free energy along a coexistence line.

Multi-stability and dynamical analysis of Zhanbota-IIA equation with couple of integrating architectures

Abstract The aim of this research is to investigate the Zhanbota-IIA equation mathematically, that has important applications in field theory, condensed matter physics, and nonlinear optics. To explore diverse types of exact traveling wave solutions, the study employs two analytical techniques namely: Nucci’s reduction method and the improved Cham technique. Consequently, the application of proposed techniques yields a variety of solitary and traveling wave solutions, including periodic singular, dark, bright and periodic types of solutions. To visualize the graphical behavior of the retrieved solutions, appropriate parametric values are used to make 2D, 3D, and contour plots. Later on, the chaotic phenomenon in a perturbed dynamical system is detected on distinct initial conditions and constant parameters through multi-stability analysis. The extracted solutions demonstrate the effectiveness, simplicity, and success of the proposed techniques in determining the precise solution of models in nonlinear fields such as engineering and optics.

Encoding the lattice in the holography

One of the most wanted features of holography in its condensed matter physics application is to encode the structure of lattice, which is the most direct data of the material. In this paper, we propose a method to encode the lattice structure by embedding the tight binding data into the Dirac equation in the anti–de Sitter bulk. We explicitly worked out the idea for the graphene and Haldane models, and the result shows that some degrees of freedom escape the free-electron on-shell curve, and Green’s function loses the pole structure completely. It implies that the electronic structure is not described by the band structure only, which is consistent with what many angle-resolved photoemission spectroscopy data tell us, and it also implies that the system is in non-Fermi liquid even for the graphene, which is consistent with recent experiments for the clean graphene. Published by the American Physical Society 2024

The moderate electron-spin interaction in Fe-intercalated NbSe2

Abstract The interaction between charge and spin degrees of freedom has always been the central issue of condensed matter physics, and transition metal dichalcogenides (TMDs) provide an ideal platform to study it benefiting from their highly tunable properties. In this article, the influence of Fe intercalation in NbSe2 was elaborately investigated using a combination of techniques. Magnetic studies have shown that the insertion of Fe atoms induces an antiferromagnetic state in which the easy axis aligned out of the plane. The sign reversal of the magnetoresistance across the Neel temperature can be satisfactorily explained by the moderate interaction between electrons and local spins. The Hall and Seebeck measurements reveal a multi-band nature, and the contribution of various phonon scattering processes is discussed based on the thermal conductivity and specific heat data.

Nickel Age of High‐Temperature Superconductivity

AbstractUnconventional high‐temperature superconductivity has long been a captivating puzzle in condensed matter physics. The 1987 Nobel Prize in Physics celebrated the discovery of high‐temperature superconductivity in copper oxide ceramics. Nearly four decades later, a broad class of high‐temperature superconducting oxides has yet to be demonstrated, and the fundamental understanding of the pairing mechanism remains inconclusive. Recently, nickel oxides have emerged as a new class of high‐temperature superconductors, beyond copper, where correlated phases can be controlled by doping, pressure, strain, and dimensionality. In this article, we provide our perspective on the recent developments and prospects of the nickel age of high‐temperature superconductivity.

The magnetic maze: a system with tunable scale invariance

Random magnetic field configurations are ubiquitous in nature. Such fields lead to a variety of dynamical phenomena, including localization and glassy physics in some condensed matter systems and novel transport processes in astrophysical systems. Here we consider the physics of a charged quantum particle moving in a “magnetic maze”: a high-dimensional space filled with a randomly chosen vector potential and a corresponding magnetic field. We derive a path integral description of the model by introducing appropriate collective variables and integrating out the random vector potential, and we solve for the dynamics in the limit of large dimensionality. We derive and analyze the equations of motion for Euclidean and real-time dynamics, and we calculate out-of-time-order correlators. We show that a special choice of vector potential correlations gives rise, in the low temperature limit, to a novel scale-invariant quantum theory with a tunable dynamical exponent. Moreover, we show that the theory is chaotic with a tunable chaos exponent which approaches the chaos bound at low temperature and strong coupling.

Cosmic thermodynamics of interacting scenario of EBEC dark matter and holographic dark energy

The current article is base on the concept of interacting dark matter in the framework of Extended Bose–Einstein condensate dark matter with the holographic dark energy model. In the scenario of dark energy and different cases of the dark matter interaction term, we discuss the behavior of the cosmological parameters, thermodynamics and thermal equilibrium conditions. To investigate the accelerated expansion or decelerated phase of the universe, we consider the observational values from literature of all parameters and graphically examine the different phases of the cosmological parameters which are deceleration, equation of state, jerk and snap parameters. We also graphically discuss the stability condition of the generalized second law of thermodynamics and thermal equilibrium condition by utilizing the observational values. We conclude that for all cases the deceleration parameter represents the accelerated behavior and for all cases the universe is stable for generalized second law of thermodynamics and for two cases the thermal equilibrium condition is stable and for third case it shows the partial stability.

Innovative analysis to the time-fractional q-deformed tanh-Gordon equation via modified double Laplace transform method

Abstract In this study, we introduce an efficient analysis of a new equation, termed the time-fractional q q -deformed tanh-Gordon equation (TGE), which is the fractional form of the q q -deformed TGE that was recently introduced by Ali and Alharbi. This equation represents a significant advancement in the field of mathematical physics, which is due to its applications in many fields including superconductivity and fiber optics. It has many applications in condensed matter physics and in modeling physical systems that exhibit violated symmetries. We investigate the q q -deformed TGE in fractional form using Caputo fractional derivative to capture non-local and memory effects, which means they can take into account the entire history of a function rather than just its current value. Notably, this equation has not been previously solved in fractional form, making our approach pioneering in its analysis. We solve this equation utilizing the modified double Laplace transform method, which is considered a semi-analytical technique that combines the double Laplace transform with Adomian polynomials to enable us to extract nonlinear terms. This method renowned for its efficacy in handling fractional differential equations; this is evident from the results obtained in the tables by comparing the analytical solution with the approximate solution we obtained, as well as by calculating the absolute error between them. We examine the existence and the uniqueness of the solution utilizing Schaefer’s fixed-point theorem. Different graphs in 2D and 3D are presented to clarify the effect of different parameters on the behavior of the solution, specially the fractional operator and the deformation parameter q q .

A Quantitative Arrott Analysis Methodology for Magnetic Susceptibility of Microscale Ferromagnetic Nanoflakes.

Probing magnetic susceptibility of a microsized ferromagnet is a long-standing problem in condensed matter physics. Among various measuring methods for magnetic susceptibility including vibrating sample magnetometry and superconducting quantum interference device magnetometry, almost all require large-scale bulk samples or thick films. However, the quantitative measurement for magnetic susceptibility on a microscale nanoflake is a great challenge. Here, we demonstrate a new analysis method to quantitatively evaluate the magnetic susceptibility of a microscale ferromagnetic nanoflake. Based on the Arrott plot of magnetization isotherms obtained from anomalous Hall resistance, we achieve an in situ evaluation of the value of magnetic susceptibility of a microscale ferromagnetic Fe5GeTe2 nanoflake, identification of the out-of-plane and in-plane magnetization, and investigation of the magnetic anisotropy transition with quantifying critical exponents. Our method reveals critical information on magnetic phase transition in microscale ferromagnetic materials, providing deep insight into spin dynamics of correlated electron systems.

Optical skyrmions and tunable fine spin structures in deep-subwavelength scale at metal/graded index material interfaces

A skyrmion is a topological quasiparticle that has been studied widely in nuclear physics, condensed matter physics, cosmology, and optics. Previously, the optical skyrmions in the surface plasmon polaritons platform were not tunable because the dielectric properties of the material were fixed. In the study, we introduce the graded refractive index materials into the near-field optical system and systematically investigate the propagation properties, dispersion relations, and spin-orbit decomposition of the surface waves at the metal/graded refractive index materials interface. Our theoretical results exhibit that the topological spin skyrmions can be formed in the system and the dimensions of optical skyrmions can be tuned by varying the central permittivity and exponent of the graded refractive index materials. Additionally, the spin fine structure, in which the spin state varies sharply from the ‘up’ state to the ‘down’ state, can be also controlled by adjusting the materials properties of the graded refractive index materials. The minimal full width of the spin fine structure is 0.254λ, which has the potential for achieving the displacement metrology with a sensitivity of 2.54 × 10−7λ theoretically. Our findings provide an extra degree of freedom to control the formation and scale of fine spin structures in optical skyrmions and open an avenue for next-generation pico-photonics.

Памяти Александра Степановича Бугаёва

Information is presented about the deceased Alexander Stepanovich Bugayov, DrSci Phys&Math, professor, Corresponding Member of the Russian Academy of Sciences since 1994 in the Department of Computer Science, Computer Engineering and Automation, full member of the Russian Academy of Sciences since 2000 in the Department of Nanotechnology and Information Technology (Section of Computing, Location, Telecommunication Systems and Element Base), founder of the Department of Solid-state Electronics and Radiophysics of the Moscow Institute of Physics and Technology, Head of the Department of Vacuum Electronics and At the same time, he is the scientific director of the MIPT Center for Open Systems and High Technologies, Head of the Laboratory of Wave Electronics of the V.A. Kotelnikov Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Deputy Director of the State Research Institute of Electronic and Ion Optics, Chief Researcher of the Department of Scientific and Innovative Activities of the South Ural State University. Professor of the Computer Engineering Department of the Higher School of Economics, Professor of the St. Petersburg State University of Aerospace Instrumentation, an outstanding specialist in the field of condensed matter physics, semiconductor physics, acoustic and spin-wave electronics, computer science and mathematical modeling of semiconductor and solid-state information processing devices. The main biographical data are given: studies at the Moscow Institute of Physics and Technology (Faculty of Physical and Quantum Electronics), postgraduate studies and work at MIPT, defense of a PhD (physical and mathematical sciences) dissertation, authorship of more than 250 scientific papers in scientific journals, participation in Russian and international conferences and seminars, editorial work in scientific journals. Work as a member of the Presidium of the Russian Academy of Sciences, membership in various Russian and international scientific societies and expert councils.

Lagrangian formulation of nuclear-electronic orbital Ehrenfest dynamics with real-time TDDFT for extended periodic systems.

We present a Lagrangian-based implementation of Ehrenfest dynamics with nuclear-electronic orbital (NEO) theory and real-time time-dependent density functional theory for extended periodic systems. In addition to a quantum dynamical treatment of electrons and selected protons, this approach allows for the classical movement of all other nuclei to be taken into account in simulations of condensed matter systems. Furthermore, we introduce a Lagrangian formulation for the traveling proton basis approach and propose new schemes to enhance its application for extended periodic systems. Validation and proof-of-principle applications are performed on electronically excited proton transfer in the o-hydroxybenzaldehyde molecule with explicit solvating water molecules. These simulations demonstrate the importance of solvation dynamics and a quantum treatment of transferring protons. This work broadens the applicability of the NEO Ehrenfest dynamics approach for studying complex heterogeneous systems in the condensed phase.

Dynamics of cosmological phase crossover during Bose–Einstein condensation of dark matter in Tsallis cosmology

During the cosmic evolution process, as the temperature of a cosmological boson gas falls below a certain threshold, a Bose–Einstein condensation process can occur at various points throughout the cosmic history of the Universe. In this model, dark matter, conceptualized as a non-relativistic, Newtonian gravitational condensate is governed by the Gross–Pitaevskii–Poisson system. In our present study, we investigate the Bose–Einstein condensation process of bosonic DM by treating it as an approximate first-order phase transition within a modified cosmological framework, known as Tsallis cosmology. We examine the evolution of relevant physical quantities characterizing the evolution dynamics of the Universe, including energy density, temperature, redshift, scale factor, Hubble parameter, and dimensionless deceleration parameter before, during, and following the Bose–Einstein condensation phase transition takes place. Additionally, we especially investigate the specific era of the evolution of the Universe characterized by a mixture of normal and condensate phases of dark matter. We analyze the behavior of temporal evolution of an important time-dependent parameter, called the condensate dark matter fraction throughout the condensation process and find the time duration of condensation of dark matter in the Tsallis cosmological model. We see that the presence of Bose–Einstein condensate dark matter in the framework of Tsallis-modified cosmology significantly alters the cosmological evolution of the Universe as compared to the standard model of cosmology. We also find for a typical value of Tsallis non-extensive parameter β=0.35\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta =0.35$$\\end{document}, the model could explain an accelerated Universe without invoking any additional energy component and solve the age problem of our Universe.

Condensable Particulate Matter Removal and Its Mechanism by Phase Change Technology During Wet Desulfurization Process

Limestone-gypsum wet flue gas desulfurization (WFGD) played a key role in SOx removal and clean emissions. However, it would also affect the condensable particulate matter (CPM) removal and compositions. The effects of the WFGD system on the removal of CPM and the contents of soluble ions in CPM were investigated in a spray desulfurization tower at varied conditions. The results indicate that the emission concentration of CPM decreased from 7.5 mg/Nm3 to 3.7 mg/Nm3 following the introduction of cold water spray and hot alkali droplet spray systems. This resulted in a CPM reduction rate of approximately 51%, reducing the percentage of CPM in total particulate matter and solving the problem of substandard particulate matter emission concentrations in some coal-fired power plants. The concentrations of NO3−, SO42−, and Cl− among the soluble ions decreased by 41–66.6%. As the liquid−to−gas ratio of the cold water spray and hot alkali droplet spray increased, CPM came into contact with more spray, which accelerated dissolution and chemical reactions. Consequently, the CPM emission concentration decreased by 17.4–19%. The liquid−to−gas ratio has a great effect on the ion concentrations of NO3−, SO42−, Cl− and NH4+, with a decrease of 28–66%. The temperatures of the cold water spray and the hot alkali droplet spray primarily affect the ionic concentrations of SO42− and Ca2+, leading to a decrease of 32.3–51%. When the SO2 concentration increased from 0 mg/Nm3 to 1500 mg/Nm3, large amounts of SO2 reacted with the desulfurization slurry to form new CPM and its precursors, the CPM emission concentration increased by 57–68.4%. This study addresses the issue of high Concentration of CPM emissions from coal-fired power plants in a straightforward and efficient manner, which is significant for enhancing the air quality and reducing hazy weather conditions. Also, it provides a theoretical basis and technical foundation for the efficient removal of CPM from actual coal-fired flue gas.