Krisztián Palotás

Krisztián Palotás
Magyar Tudományos Akadémia Wigner Fizikai Kutatóközpont · Institute for Solid State Physics and Optics

MSc, PhD, MSc

About

94
Publications
13,311
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2,125
Citations
Introduction
Research interests: Physics/Chemistry: - Magnetic surfaces and nanostructures, topological magnetic objects (skyrmions) - 2D materials, new materials for various applications - Supported molecular nanostructures - Development of theoretical electron charge/spin transport methods based on first principles, and simulations in the tunneling and ballistic regime; STM/STS simulations - Ab initio electronic structure calculations (DFT)
Additional affiliations
January 2019 - present
January 2016 - December 2018
Slovak Academy of Sciences
Position
  • Fellow
April 2009 - present
Budapest University of Technology and Economics
Position
  • Electron transport & magnetism theory

Publications

Publications (94)
Article
Full-text available
On the occasion of its 25th anniversary, we revise Chen's derivative rule for electron tunneling [C.J. Chen, Phys. Rev. B 42, 8841 (1990)] for the purpose of computationally efficient simulations of scanning tunneling microscopy (STM) based on first principles electronic structure data. The revised model allows the weighting of tunneling matrix ele...
Article
Full-text available
We introduce a method for a combined calculation of charge and vector spin transport of elastically tunneling electrons in magnetic scanning tunneling microscopy (STM). The method is based on the three-dimensional Wentzel-Kramers-Brillouin (3D-WKB) approach combined with electronic structure calculations using first principles density functional th...
Article
Full-text available
Tunneling spin transport characteristics of a magnetic skyrmion are described theoretically in magnetic scanning tunneling microscopy (STM). The spin-polarized charge current in STM (SP-STM) and tunneling spin transport vector quantities, the longitudinal spin current and the spin transfer torque are calculated in high spatial resolution within the...
Article
Full-text available
Based on a combined charge and vector spin transport theory capable of imaging noncollinear magnetic textures on surfaces with spin-polarized scanning tunneling microscopy (SP-STM), the high-resolution tunneling electron charge and spin transport properties of a variety of N\'eel- and Bloch-type skyrmions are investigated. Axially symmetric skyrmio...
Article
Full-text available
High-resolution tunneling electron spin transport properties (longitudinal spin current (LSC) and spin transfer torque (STT) maps) of topologically distinct real-space magnetic skyrmionic textures are reported by employing a 3D-WKB combined scalar charge and vector spin transport theory in the framework of spin-polarized scanning tunneling microsco...
Article
Full-text available
The crystallographic and magnetic properties of an Fe monolayer (ML) grown on 2 ML Au/W(110) substrate are studied with spin-polarized low-energy electron microscopy, density functional theory, and relativistic screened Korringa–Kohn–Rostoker calculations. The single layer of iron atoms possesses hexagonal symmetry and reveals a ferromagnetic order...
Article
The van der Waals (vdW) heterojunction often reveals unexpected characteristics distinct from conventional junctions. We investigate an emergent interface phenomenon between monolayer ReSe2 and graphene via combined studies of scanning tunneling microscopy (STM) and density functional theory (DFT). When probing monolayer ReSe2 on graphene at bias v...
Article
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Experimental scanning tunneling microscopy (STM) images of the hematite (0001) surface exhibit long-range superstructures formed by coexisting domains consisting of different terminations (α, β, γ) of the α-Fe2O3(0001) surface. In this work extensive simulations of STM images of different terminations of hematite (0001) surfaces are performed and c...
Article
Accurate atomistic models for metal/oxide interfaces play a pivotal role in determining copper-based interfacial processes, ranging from electronic circuitry wirings to chemical catalysis. The “29” and “44” surfaces represent two of the most classical embryonic oxides on Cu(111). Although many attempts have been made to offer detailed atomistic mod...
Preprint
We report on the structural and magnetic properties of single and double atomic layers of Mn on a clean and unreconstructed Nb(110) substrate. Low-temperature scanning tunneling spectroscopy measurements reveal a proximity-induced superconducting state in the Mn thin films, which are found to grow pseudomorphically on the Nb surface. Spin-polarized...
Article
Over the past decades, the rational synthesis of two-dimensional covalent organic framework (2D COFs) monolayer via on-surface chemistry has been widely explored. Herein, we propose the [2+2] photocycloaddition as a novel strategy for large-scale fabrication of COFs from theoretical perspective. Thanks to the symmetry forbidden of thermal [2+2] cyc...
Article
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We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic chains are determined by the nearest-neighbor isotropic interaction....
Preprint
Full-text available
We present results for the electronic and magnetic structure of Mn and Fe clusters on Nb(110) surface, focusing on building blocks of atomic chains as possible realizations of topological superconductivity. The magnetic ground states of the atomic dimers and most of the monatomic chains are determined by the nearest-neighbor isotropic interaction....
Article
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Magnetic atoms coupled to the Cooper pairs of a superconductor induce Yu-Shiba-Rusinov states (in short Shiba states). In the presence of sufficiently strong spin-orbit coupling, the bands formed by hybridization of the Shiba states in ensembles of such atoms can support low-dimensional topological superconductivity with Majorana bound states local...
Article
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Condensed-matter physics: Strain causes a change in charge patterns Researchers in South Korea, Hungary and Sweden have shown how strain influences the electronic patterns formed in two-dimensional materials. Some of the stranger properties of crystalline solids arise when electric charges organise themselves into ordered patterns. Charge density w...
Preprint
Magnetic atoms coupled to the Cooper pairs of a superconductor induce Yu-Shiba-Rusinov states (in short Shiba states). In the presence of sufficiently strong spin-orbit coupling, the bands formed by hybridization of the Shiba states in ensembles of such atoms can support low-dimensional topological superconductivity with Majorana bound states local...
Article
In electrochemical systems, upon applying an electrode potential, complicated surface reconstructions between halogen atoms (iodide anion) and the metal substrate (copper facet) have been observed from the ordered halide adlayers to ultrathin metal halide films. Although the global geometry of the ultrathin CuI film on Cu(111) was proposed, the loc...
Article
Full-text available
Adsorption properties of azobenzene - the prototypical molecular switch – was investigated on hexagonal boron nitride (h-BN) monolayer (“nanomesh”) prepared on Rh(111). The h-BN layer was produced by decomposing borazine (B3N3H6) at 1000-1050 K. Temperature programmed desorption (TPD) studies revealed that azobenzene molecules adsorbed on the “wire...
Preprint
Full-text available
High-resolution tunneling electron spin transport properties (longitudinal spin current and spin transfer torque (STT) maps) of topologically distinct real-space magnetic skyrmionic textures are reported by employing a 3D-WKB combined scalar charge and vector spin transport theory in the framework of spin-polarized scanning tunneling microscopy (SP...
Article
The electrocatalytic reduction of nitrogen (N2) has recently emerged as an attractive technology for producing ammonia (NH3) at mild conditions. Nevertheless, achieving a high selectivity of N2 reduction with respect to the hydrogen evolution at relatively low overpotential, and thus increasing the energy efficiency of ammonia production, has remai...
Article
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Controlled shape and size distribution of metal nanoparticles for surface catalytic reactions are important. Through deposition onto the periodic surface of h-BN we can adjust these parameters of gold thereby we are able to influence the catalytic activity of the nanoparticles. In this study we investigated the decomposition of ethanol on gold nano...
Article
Full-text available
Magnetic atoms on heavy-element superconducting substrates are potential building blocks for realizing topological superconductivity in one- and two-dimensional atomic arrays. Their localized magnetic moments induce so-called Yu-Shiba-Rusinov (YSR) states inside the energy gap of the substrate. In the dilute limit, where the electronic states of th...
Preprint
Recent development of the magnetic material engineering led to achievement of the systems with a high interfacial Dzyaloshinskii-Moriya interaction (DMI). As a result, the formation of non-collinear magnetic soliton states or nonreciprocal spin wave dynamics is achievable. Typically used materials are based on bi-layers Heavy Metal/Ferromagnet, e.g...
Article
Full-text available
We present results of first-principles calculations of the magnetic properties of Fe chains deposited on the Re(0001) surface. By increasing the length of the chain, a transition is found from an almost collinear antiferromagnetic state for a five-atom-long chain to a spin spiral state with the rotational plane slightly tilted from the surface of t...
Article
Cu2O has been investigated for decades to understand the complex nature of oxidation and to utilize its high catalytic activity and intrinsic p-type character. However, the structures and intrinsic defects of Cu2O(111) surfaces have not been fully explored at the atomistic level, which is required to clarify some issues such as termination of Cu2O(...
Preprint
Magnetic atoms on heavy-element superconducting substrates are potential building blocks for realizing topological superconductivity in one- and two-dimensional atomic arrays. Their localized magnetic moments induce so-called Yu-Shiba-Rusinov (YSR) states inside the energy gap of the substrate. In the dilute limit, where the electronic states of th...
Article
The synthesis of nitrogen-doped single-layer graphene has been achieved on the copper surface by using the nitrogen-containing sole precursor azafullerene. The synthesis process, doping properties, and doping-induced variation of local work function of graphene have been investigated on the atomic scale by combing scanning tunneling microscopy/spec...
Article
Ultrathin oxidic layers of Mo (i.e. O/Mo) on the Au(111) substrate are investigated using first-principles density-functional theory calculations. Various polymorphic structural models of these O/Mo layers are proposed and compared with previous experimental results -- covering both spectroscopic and microscopic approaches of characterization. We f...
Article
We study the limits of SPM subatomic resolution in imaging orbital magnetic features on a model system of a Co atom on a p(2 × 1)Cu(110):O surface. We show that scanning tunneling spectroscopies allow the determination of the occupation of the Co d shells and the value of the Hubbard U in the DFT + U modeling, and that standard near-contact AFM can...
Article
The coordination-restricted ortho-site C–H bond activation and dehydrogenative homocoupling of 4,4’-(1,3-phenylene)dipyridine (1,3-BPyB) and 4,4’-(1,4-phenylene)dipyridine (1,4-BPyB) on different metal surfaces were studied by a combination of scanning tunneling microscopy, non-contact atomic force microscopy and density functional theory calculati...
Preprint
Full-text available
We present results of first-principles calculations of the magnetic properties of Fe chains deposited on the Re(0001) surface. By increasing the length of the chain, a transition is found from an almost collinear antiferromagnetic state for a 5-atom-long chain to a spin spiral state with the rotational plane slightly tilted from the surface of the...
Article
Full-text available
We report on the investigation of the atomic and electronic structures of a clean Si(331)-(12 × 1) surface using a first-principles approach with both plane wave and strictly localized basis sets. Starting from the surface structure proposed by Zhachuk and Teys [Phys. Rev. B 95, 041412(R) (2017)], we develop significant improvements to the atomic m...
Article
Full-text available
Ultrathin transition metal oxide films exhibit unique physical and chemical properties not observed for the corresponding bulk oxides. These properties, originating mainly from the limited thickness and the interaction with the support, make those films similar to other supported 2D materials with bulk counterparts, such as transition metal dichalc...
Article
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Based on ab initio calculations and spin dynamics simulations, we perform a detailed study on the magnetic properties of bulk MnN and the MnN/Fe interface. We determine the spin model parameters for the θ-phase of bulk MnN, and we find that the competition between the nearest and the next-nearest-neighbor interactions leads to antiferromagnetic ord...
Article
Surface alloying is an important technique to change their chemical properties. In this study, by employing density functional theory (DFT) calculations, the atomic arrangements and energetics of an extensive set of Au–Rh structures in a confined (2×1) surface cell on a Rh(111) substrate are investigated. An ordered surface alloy layer composed of...
Article
It is known that the hexagonal boron nitride (h-BN) monolayer has a periodically corrugated structure on Rh(111), termed “nanomesh”, while the h-BN layer is planar on close packed surfaces of coinage metals (Cu, Ag, Au) due the weak interaction. Our studies aimed at understanding the metal-h-BN interaction, when both Rh and Au are present. On the o...
Article
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Realizing Majorana bound states (MBS) in condensed matter systems is a key challenge on the way toward topological quantum computing. As a promising platform, one-dimensional magnetic chains on conventional superconductors were theoretically predicted to host MBS at the chain ends. We demonstrate a novel approach to design of model-type atomic-scal...
Preprint
Full-text available
Based on a combined charge and vector spin transport theory capable of imaging noncollinear magnetic textures on surfaces with spin-polarized scanning tunneling microscopy (SP-STM), the high-resolution tunneling electron charge and spin transport properties of a variety of Néel-and Bloch-type skyrmions are investigated. Axially symmetric skyrmions...
Article
Full-text available
Magnetic skyrmions are localized nanometer-sized spin configurations with particle_like properties, which are envisioned to be used as bits in next_generation information technology. An essential step towards future skyrmion-based applications is to engineer key magnetic parameters for developing and stabilizing individual magnetic skyrmions. Here...
Article
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Using first-principles calculations, we study the magnetic properties of a Co monolayer on a Pt(111) surface with a capping monolayer of selected $5d$ elements (Re, Os, Ir, Pt and Au). First we determine the tensorial exchange interactions and magnetic anisotropies characterizing the Co monolayer for all considered systems. We find a close relation...
Article
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The correct identification of topological magnetic objects in experiments is an important issue. In the present paper we report on the characterization of metastable skyrmionic spin structures with various topological charges (Q=−3,−2,−1,0,+1,+2) in the (Pt1−xIrx)Fe/Pd(111) ultrathin magnetic film by performing spin-polarized scanning tunneling mic...
Article
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We observe metastable localized spin configurations with topological charges ranging from Q=−3 to Q=2 in a (Pt0.95Ir0.05)/Fe bilayer on a Pd(111) surface by performing spin dynamics simulations, using a classical Hamiltonian parametrized by ab initio calculations. We demonstrate that the frustration of the isotropic exchange interactions is respons...
Article
The inherent instability of CH3NH3PbX3 perovskite remains a major technical barrier for the industrial applications of perovskite materials. Recently, the most stable surface structures of CH3NH3PbX3 have been successfully characterized by using Density Functional Theory (DFT) calculations together with the high-resolution scanning tunneling micros...
Article
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We perform a study of domain walls in Co/Ir$_n$/Pt(111) (n = 0,1,...,6) films by a combined approach of first-principles calculations and spin dynamics simulations. We determine the tensorial exchange interactions and the magnetic anisotropies for the Co overlayer in both FCC and HCP geometries, depending on the number of Ir buffer layers. We find...
Article
Full-text available
Scanning tunneling microscopy (STM) measurements of the (110) surface of magnetite showed the coexistence of two reconstructions: the known (1×3) row reconstruction and a surprising atomic structure of high complexity which occupies a small fraction of the surface. Oxygen vacancies on the Fe3O4(110) B-terminated surface have previously been determi...
Article
Rutile-monoclinic phase transitions of vanadium oxide (VO2) nanocrystals adsorbed on graphene-based substrates are of current scientific interest, although their adsorption and growth mechanisms have not been investigated theoretically. In this study, we use density functional theory (DFT) calculations for determining the binding energies and predi...
Article
Geometric and electronic characterizations of one monolayer rhodium with Nishiyama-Wassermann (NW) structure on Mo(110) substrate have been performed by density functional theory (DFT) calculations. In the NW structure the Rh atoms form a wavy structure propagating along the [001] direction, characterized by an amplitude of 0.26 Å in the [1-10] dir...
Article
In biomineralization, inorganic materials are formed with remarkable control of the shape and morphology. Chirality, as present in the biomolecular world, is therefore also common for biominerals. Biomacromolecules, like proteins and polysaccharides, are in direct contact with the mineral phase and act as modifiers during nucleation and crystal gro...
Article
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We determined the magnetic B-T phase diagram of PdFe bilayer on Ir(111) surface by performing Monte Carlo and spin dynamics simulations based on an effective classical spin model. The parameters of the spin model were determined by ab initio methods. At low temperatures we found three types of ordered phases, while at higher temperatures, below the...
Article
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Energy-dependent apparent step heights of two-dimensional ultrathin Pb islands grown on the Si(111)6×6−Au surface have been investigated by a combination of scanning tunneling microscopy, first-principles density-functional theory, and the particle-in-a-box model calculations. The apparent step height shows the thickness- and energy-dependent oscil...
Article
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The mechanism of attachment of nanocrystals (NCs) to curved carbonaceous species such as graphene nanoribbons and carbon nanotubes (CNTs) is of current scientific interest. In addition, we have observed anisotropic growth patterns of titania NCs from carbonaceous materials, for which there is no theoretical explanation. In this work, we use density...
Article
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Motivated by a recent experimental observation of a complex magnetic structure [Takada et al. 2013 J. Magn. Magn. Mater. 329 95] we present a theoretical study of the magnetic structure of an Fe monolayer deposited on Rh(001). We use a classical spin Hamiltonian with parameters obtained from ab initio calculations and go beyond the usual anisotropi...
Article
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We introduce a statistical correlation analysis method to obtain information on the local geometry and orientation of the tip used in scanning tunneling microscopy (STM) experiments based on large scale simulations. The key quantity is the relative brightness correlation of constant-current topographs between experimental and simulated data. This c...
Article
We review the recently developed three-dimensional (3D) atom-superposition approach for simulating scanning tunneling microscopy (STM) and spectroscopy (STS) based on ab initio electronic structure data. In the method, contributions from individual electron tunneling transitions between the tip apex atom and each of the sample surface atoms are sum...
Article
Full-text available
Highly oriented pyrolytic graphite (HOPG) is an important substrate in many technological applications and is routinely used as a standard in Scanning Tunnelling Microscopy (STM) calibration, which makes the accurate interpretation of the HOPG STM contrast of great fundamental and applicative importance. We demonstrate by STM simulations based on e...
Article
Full-text available
We perform an extensive study of the spin-configurations in a PdFe bilayer on Ir(111) in terms of ab initio and spin-model calculations. We use the spin-cluster expansion technique to obtain spin model parameters, and solve the Landau-Lifshitz-Gilbert equations at zero temperature. In particular, we focus on effects of layer relaxations and the evo...
Article
Full-text available
We extend the orbital-dependent electron tunneling model implemented within the three-dimensional (3D) Wentzel-Kramers-Brillouin (WKB) atom-superposition approach to simulate spin-polarized scanning tunneling microscopy (SP-STM) above magnetic surfaces. The tunneling model is based on the electronic structure data of the magnetic tip and surface ob...
Article
The one-dimensional diffusion of individual Pb atoms on the Si(553)-Au surface has been investigated by a combination of scanning tunneling microscopy (STM), spectroscopy (STS), and first-principles density functional theory. The obtained results unambiguously prove that the diffusion channels are limited to a narrow region between Au chains and st...
Article
Full-text available
We present a detailed first principles study on the magnetic structure of an Fe monolayer on different surfaces of 5d transition metals. We use the spin-cluster expansion technique to obtain parameters of a spin model, and predict the possible magnetic ground state of the studied systems by employing the mean field approach and in certain cases by...
Article
Graphene substrates are known to have randomly located functional groups on their surface, particularly at their edges, including carboxylate, carbonyl, epoxy, and alcohol functionalities. However, the detailed interactions of these graphene functionalities with metal oxide nanoclusters are unexplored. This work examined the interaction of titania...