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arXiv 2022年

作者： Zegrodnik, Michal Wójcik, P. Academic Centre for Materials and Nanotechnology AGH University of Science and Technology Al. Mickiewicza 30 Krakow30-059 Poland AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow30-059 Poland Al. Mickiewicza 30 Krakow30-059 Poland

We analyze the real-space paired state with the k-dependent superconducting gap in the presence of Rashba type spin-orbit coupling and external magnetic field. We show that the extended s-wave pairing symmetry is the most probable scenario to appear in the low-electron concentration regime. According to our study, the van Hove singularity induced by the spin-orbit coupling may lead to a significant enhancement of the superconducting gap, critical temperature and critical magnetic field. Moreover, the combined effect of the spin-orbit coupling and the external magnetic field results in a non-zero total momentum of the Cooper pairs, which is a characteristic feature of the so-called helical state. In such situation, due to the C4 symmetry breaking, a small d-wave and p-wave contributions to the pairing appear, which significantly change the character of the helical state. The obtained results are discussed in the context of the experimental data related with the unconventional superconducting features of the transition metal oxide interfaces as well as the recently reported supercurrent diode effect. Copyright © 2022, The Authors. All rights reserved.

关键词： Transition metals

Disformal symmetry in the Universe: mimetic gravity and beyond

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arXiv 2023年

作者： Domènech, Guillem Ganz, Alexander Institute for Theoretical Physics Leibniz University Hannover Appelstraße 2 Hannover30167 Germany Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Symmetries play an important role in fundamental physics. In gravity and field theories, particular attention has been paid to Weyl (or conformal) symmetry. However, once the theory contains a scalar field, conformal transformations of the metric can be considered a subclass of a more general type of transformation, so-called disformal transformation. Here, we investigate the implications of pure disformal symmetry in the Universe. We derive the form of general disformal invariant tensors from which we build the most general disformal invariant action. We argue that, in cosmology, disformal symmetry amounts to require that the lapse function is fully replaced by a (time-like) scalar field at the level of the action. We then show that disformal symmetry is in general an exactly equivalent formulation of general mimetic gravity. Lastly, we go beyond mimetic gravity and find that a particular class of invariance leads to seemingly Ostrogradski-like (with higher derivatives) Lagrangians, which are nevertheless absent of Ostrogradski ghosts in a cosmological background, despite having an additional degree of freedom. We also propose an application of our formalism to find new invertible disformal transformations, where the coefficient involves higher derivatives and curvature, further expanding the theory space of scalar-tensor theories. Copyright © 2023, The Authors. All rights reserved.

关键词： Tensors

Rényi entanglement entropy of a spin chain with generative neural networks

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Physical Review E 2024年第4期110卷 044116页

作者： Piotr Białas Piotr Korcyl Tomasz Stebel Dawid Zapolski Institute of Applied Computer Science <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 11 30-348 Kraków Poland. Institute of Theoretical Physics <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 11 30-348 Kraków Poland. Faculty of Mathematics and Computer Science <a href="https://***/03bqmcz70">Jagiellonian University</a> ul. Łojasiewicza 6 30-348 Kraków Poland.

We describe a method to estimate Rényi entanglement entropy of a spin system which is based on the replica trick and generative neural networks with explicit probability estimation. It can be extended to any spin system or lattice field theory. We demonstrate our method on a one-dimensional quantum Ising spin chain. As the generative model, we use a hierarchy of autoregressive networks, allowing us to simulate up to 32 spins. We calculate the second Rényi entropy and its derivative and cross-check our results with the numerical evaluation of entropy and results available in the literature.

关键词： Entanglement entropy Quantum statistical mechanics Deep learning Information theory Ising model Monte Carlo methods Neural network simulations

Strong-coupling superconductivity of SrIr2 and SrRh2: Phonon engineering of metallic Ir and Rh

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Physical Review B 2021年第5期104卷 054505-054505页

作者： Sylwia Gutowska Karolina Górnicka Paweł Wójcik Tomasz Klimczuk Bartlomiej Wiendlocha Faculty of Physics and Applied Computer Science AGH University of Science and Technology Aleja Mickiewicza 30 30-059 Krakow Poland Faculty of Applied Physics and Mathematics and Advanced Materials Centre Gdansk University of Technology ul. Narutowicza 11/12 80-233 Gdańsk Poland

Experimental and theoretical studies on superconductivity in SrIr2 and SrRh2 Laves phases are presented. The measured resistivity, heat capacity, and magnetic susceptibility confirm the superconductivity of these compounds with Tc=6.07 and 5.41 K, respectively. Electronic structure calculations show that the Fermi surface is mostly contributed by 5d (4d) electrons of Ir (Rh), with Sr atoms playing the role of electron donors. The effect of the spin-orbit coupling is analyzed and found to be important in both materials. Lattice dynamics and electron-phonon coupling (EPC) are studied and the strong electron-phonon interaction is found, contributed mostly by the low-frequency Ir and Rh vibrations. The enhancement of EPC, when compared to weakly coupled metallic Ir and Rh, is explained by the strong modifications in the propagation of phonons in the network of Ir (Rh) tetrahedrons, which are the building blocks of the Laves phase, and originate from the metallic fcc structures of elemental iridium and rhodium.

关键词： Electron-phonon coupling Electronic structure Superconductivity Transition metals Density functional theory

Cleaning large-dimensional covariance matrices for correlated samples

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Physical Review E 2022年第3期105卷 034136-034136页

作者： Zdzislaw Burda Andrzej Jarosz AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 30-059 Kraków Poland CRISIL Irevna Poland Sp z o.o. ul. Świętego Mikołaja 7 50-529 Wrocław Poland

We elucidate the problem of estimating large-dimensional covariance matrices in the presence of correlations between samples. To this end, we generalize the Marčenko-Pastur equation and the Ledoit-Péché shrinkage estimator using methods of random matrix theory and free probability. We develop an efficient algorithm that implements the corresponding analytic formulas based on the Ledoit-Wolf kernel estimation technique. We also provide an associated open-source Python library, called shrinkage, with a user-friendly API to assist in practical tasks of estimation of large covariance matrices. We present an example of its usage for synthetic data generated according to exponentially decaying autocorrelations.

关键词： Random matrix theory

The In-Plane Band Bending Effect Around AU Islands Grown on the Bi2te3 Topological Insulator

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SSRN

SSRN 2023年

作者： Naumov, Andrii Chrobak, Maciej Trembulowicz, Artur Jurczyszyn, Michal Maćkosz, Krzysztof Stępień, Joanna Sikora, Marcin Przybylski, Marek Academic Centre for Materials and Nanotechnology Poland Faculty of Physics and Applied Computer Science AGH University of Krakow Mickiewicza Av. 30 Krakow30-059 Poland Institute of Experimental Physics University of Wroclaw pl. M. Borna 9 Wroclaw50-204 Poland Empa-Swiss Federal Laboratories for Materials Science and Technology Laboratory for Mechanics of Materials and Nanostructures Feuerwerkerstrasse 39 ThunCH-3602 Switzerland AGH University of Science and Technology Poland

We have utilized scanning tunneling microscopy and spectroscopy (STM/STS) as well as x-ray linear dichroism (XLD) along with DFT calculations to determine the structural and electronic changes of the gold-covered nonstoichiometric Bi2Te3 single crystal surface. XLD spectra supported by a numerical simulation of several configurations show that at low coverage ( 1.0 ML) mixing at the Au/Bi2Te3 interface may occur. For local electronic characterization around stand-alone Au islands, small coverages were selected for which the inter-island distance is large enough to avoid overlapping island-wide effects. STS spectra reveal that for small coverages the topological surface states (TSS) are preserved. However, at a distance of about 10 nm from an Au island, by approaching the islands, the electronic structure gradually changes. This is manifested by a gradual shift of the STS spectra to more negative energies with respect to the pristine surface. The results are discussed in view of possible Au-Bi2Te3 mixing, a local charge transfer and the presence of in-plane downward band bending. © 2023, The Authors. All rights reserved.

关键词： Electronic structure

On-demand electrohydrodynamic jetting of an ethylene glycol and water mixture-system of controlled picoliter fluid deposition

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On-demand electrohydrodynamic jetting of an ethylene glycol ...

Printing for Fabrication 2021

作者： Dijksman, J.F. Stachewicz, U. University of Twente Faculty Science and Technology Physics of Fluids Drienerlolaan 5 Enschede7522 NB Netherlands AGH University of Science and Technology Faculty of Metals Engineering and Industrial Computer Science Al. A. Mickiewicza 30 Kraków30-059 Poland

ISBN: (纸本)9780892083565

On-demand electrohydrodynamic jetting also called electrohydrodynamic atomization (EHDA) is a method to jet small amounts of fluid out of a nozzle with a relatively large diameter by switching on and off an electrical field between the nozzle and the substrate. The total amount of volume deposited is up to 5 pL. The set-up consists of a vertically placed glass pipette with a small nozzle directed downward and a flat substrate placed close to the end of the nozzle. Inside the pipette, an electrode is mounted close to the entrance of the nozzle. The electrode is connected to a high voltage power amplifier. Upon switching on the electrical field, the apparent surface tension drops, the meniscus deforms into a cone and fluid starts to flow toward the nozzle deforming the meniscus. At a certain moment the cone reaches the Taylor cone dimensions and from its tip a jet emerges that decomposes into a stream of charged fL droplets that fly toward the substrate. This process stops when the pulse is switched off. After switching off, the meniscus returns slowly to its equilibrium position. The process is controlled by different time constants, such as the slew rate of the power amplifier and the RC time of the electrical circuit composed of the electrical resistance in the fluid contained in the nozzle between the electrode and the meniscus, and the capacitance of the gap between the meniscus and the flat substrate. Another time constant deals with the fluid flow during the growth of the meniscus, directly after switching on the pulse. This fluid flow is driven by hydrostatic pressure and opposed by a viscous drag in the nozzle. The final fluid flow during droplet formation is governed by the balance between the drag of the charge carriers inside the fluid, caused by the current associated with the charged droplets leaving the meniscus and the viscous drag. These different phenomena will be discussed theoretically and compared to experimental results. © Society for Imaging Sci

关键词： Electrodes

A Comprehensive Study of Double pion Photoproduction: A Regge Approach 10

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A Comprehensive Study of Double pion Photoproduction: A Regg...

10th International Conference on Quarks and Nuclear physics, QNP 2024

作者： Hammoud, Nadine Bibrzycki, Lukasz Mathieu, Vincent Perry, Robert J. Szczepaniak, Adam P. Departament de Física Quàntica i Astrofísica Institut de Ciències del Cosmos Universitat de Barcelona BarcelonaE-08028 Spain AGH University of Krakow Faculty of Physics and Applied Computer Science al. Mickiewicza 30 KrakówPL-30059 Poland Departamento de Física Teórica Universidad Complutense de Madrid IPARCOS MadridE-28040 Spain Theory Center Thomas Jefferson National Accelerator Facility Newport NewsVA23606 United States Center for Exploration of Energy and Matter Indiana University BloomingtonIN47403 United States Department of Physics Indiana University BloomingtonIN47405 United States

Presented here is a theoretical model designed to investigate double pion photoproduction, within the photon energy range of 3.0 to 3.8 GeV and momentum transfer range of 0.4 2. This model integrates contributions from resonances such as the ρ(770), as well as the primary background from the Deck mechanism. Utilizing the Regge formalism and incorporating the established Deck mechanism, the model emphasizes the significance of the ρ(770) resonance, highlighting its role in representing P-wave contributions arising from pomeron alongside other exchanges. However, at high momentum transfers, indications of s-channel helicity non-conservation emerge, suggesting the involvement of additional partial waves, notably the S and D waves. The model is further extended to include scalar mesons such as f0(500), f0(980), and f0(1370), along with the tensor meson f2(1270), influencing S- and D-wave effects, respectively. Predictions of angular moments are compared with CLAS data, and the analysis further explores the t-dependence of the Regge amplitude residue function for subdominant exchanges. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0).

关键词： Momentum transfer

Kinetics of transformation, border of metastable miscibility gap in Fe-Cr alloy and limit of Cr solubility in iron at 858 K

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arXiv 2022年

作者： Dubiel, Stanislaw M. Żukrowski, Jan AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. A. Mickiewicza 30 Kraków30-059 Poland AGH University of Science and Technology Academic Center for Materials and Nanotechnology al. A. Mickiewicza 30 Kraków30-059 Poland

The study was aimed at determination of the position of the Fe-rich border of the metastable miscibility gap (MMG) and of the solubility limit of Cr in iron at 858 K. Towards this end a Fe73.7Cr26.3 alloy was isothermally annealed at 858 K in vacuum up to 8144 hours and Mössbauer spectra were recorded at room temperature after every step of the annealing. Three spectral parameters viz. the average hyperfine field, , the average isomer shift, , and the probability of the atomic configuration with no Cr atoms in the two-shell vicinity of the probe Fe atoms, P(0,0), gave evidence that the transformation process takes place in two stages. All three parameters could have been well described in terms of the Johnson-Mehl-Avrami-Kolmogorov equation, yielding kinetics parameters. The first stage, associated with the phase decomposition, proceeded much faster than the second stage, associated with the alpha-to-sigma phase transformation. The most reliable estimation of the position of the MMG and that of the value of the Cr solubility limit was obtained from the annealing time dependence of , namely 24.5 at.% Cr for the former and 20.3 at.% Cr for the latter. A comparison of these figures with the recent phase diagrams pertinent to Fe-Cr system was done. © 2022, CC BY-NC-ND.

关键词： Binary alloys

Spin wave interactions in the pyrochlore Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions

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arXiv 2025年

作者： Jyothis, V.V. Mondal, Kallol Mavani, Himanshu Chandra, V. Ravi School of Physical Sciences National Institute of Science Education and Research Bhubaneswar Odisha Jatni752050 India Homi Bhabha National Institute Training School Complex Anushaktinagar Mumbai400094 India AGH University of Krakow Faculty of Physics and Applied Computer Science Aleja Mickiewicza 30 Krakow30-059 Poland Department of Physics and Astronomy Nebraska Center for Materials and Nanoscience University of Nebraska LincolnNE68588-0299 United States

We study the effect of magnon interactions on the spin wave spectra of the all-in-all-out phase of the pyrochlore nearest neighbour antiferromagnet with a Dzyaloshinskii-Moriya interaction (D). The leading order corrections to spin wave energies indicate a significant renormalisation for commonly encountered strengths of the Dzyaloshinskii-Moriya term. For low values of D we find a potential instability of the phase itself, indicated by the renormalisation of magnon frequencies to negative values. We have also studied the renormalized spectra in the presence of magnetic fields along three high symmetry directions of the lattice, namely the [111], [100] and [110] directions. Generically, we find that for a fixed value of the Dzyaloshinskii-Moriya interaction renormalized spectra for the lowest band decrease with an increasing strength of the field. We have also analyzed the limits of the two magnon continuum and probed the possibility of magnon decay. For a range of D and the field strength we identify possible parameter regimes where the decay of the higher bands of the system are kinematically allowed. © 2025, CC BY-NC-ND.

关键词： Spin waves