The stability and electronic structure of competing silicene phases under in-plane compressive stress, either free-standing or on the ZrB$_2$(0001) surface, has been studied by first-principles calculations. A particular ($\sqrt{3}\times\sqrt{3}$)-reconstructed structural modification was found to be stable on the ZrB$_2$(0001) surface under epitaxial conditions. In contrast to the planar and buckled forms of free-standing silicene, in this "planar-like" phase, all but one of the Si atoms per hexagon reside in a single plane. While without substrate, for a wide range of strain, this phase is energetically less favorable than the buckled one, it is calculated to represent the ground state on the ZrB$_2$(0001) surface. The atomic positions are found to be determined by the interactions with the nearest neighbor Zr atoms competing with Si-Si bonding interactions provided by the constraint of the honeycomb lattice.
We have carried out first-principles based DFT calculation on electronic properties of silicene monolayer on various (111) semi-conducting surfaces. We find that the relative stability and other properties of the silicene overlayer depends sensitively on whether the interacting top layer of the substrate is metal or non-metal terminated. The nature of silicene-monolayer on the metal termi- nated surface can be metallic or even magnetic, depending upon the choice of the substrate. The silicene overlayer undergoes n-type doping on metal terminated surface while it undergoes p-type doping on non …
Silicene, as the silicon analog of graphene, has been successfully fabricated by epitaxial growing on various substrates. Similar to free-standing graphene, free-standing silicene possesses a honeycomb structure and Dirac-cone-shaped energy band, resulting in many fascinating properties such as high carrier mobility, quantum spin Hall effect, quantum anomalous Hall effect, and quantum valley Hall effect. The maintenance of the honeycomb crystal structure and the Dirac cone of silicene is crucial for observation of its intrinsic properties. In this review, we systematically discuss the substrat…
The band structure of the recently synthesized (3$\times$3) silicene monolayer on (4$\times$4) Ag(111) is investigated using density functional theory. A $k$-projection technique that includes the $k_\bot$-dependence of the surface bands is used to separate the contributions arising from the silicene and the substrate, allowing a consistent comparison between the calculations and the angle-resolved photoemission experiments. Our calculations not only reproduce the observed gap and linear dispersion across the K point of (1$\times$1) silicene, but also demonstrate that these originate from the …
We propose a guideline for exploring substrates that stabilize the monolayer honeycomb structure of silicene and germanene while simultaneously preserve the Dirac states: in addition to have a strong binding energy to the monolayer, a suitable substrate should be a large-gap semiconductor with a proper workfunction such that the Dirac point lies in the gap and far from the substrate states when their bands align. We illustrate our idea by performing first-principles calculations for silicene and germanene on the Al-terminated (0001) surface of Al2O3 . The overlaid monolayers on Al-terminated A…
The electronic structure of the recently synthesised (3x3) reconstructed silicene on (4x4) Ag(111) is investigated by first-principles calculations. New states emerge due to the strong hybridization between silicene and Ag. Analyzing the nature and composition of these hybridized states, we show that i) it is possible to clearly distinguish them from states coming from the Dirac cone of free-standing silicene or from the sp-bands of bulk Ag and ii) assign their contribution to the description of the linearly dispersing band observed in photoemission. Furthermore, we show that silicene atoms co…
Absence of the Dirac cone due to a strong band hybridization is revealed to be a common feature for epitaxial silicene on metal substrates according to our first-principles calculations for silicene on Ir, Cu, Mg, Au, Pt, Al, and Ag substrates. The destroyed Dirac cone of silicene, however, can be effectively restored with linear or parabolic dispersion by intercalating alkali metal atoms between silicene and the metal substrates, offering an opportunity to study the intriguing properties of silicene without further transfer of silicene from the metal substrates.
For most practical applications in electronic devices, two-dimensional materials should be transferred onto semiconducting or insulating substrates, since they are usually generated on metallic substrates. However, the transfer often leads to wrinkles, damages, contaminations and so on which would destroy the intrinsic properties of samples. Thus, generating two-dimensional materials directly on nonmetallic substrates has been a desirable goal for a long time. Here, via a swarm structure search method and density functional theory, we employed an insulating N-terminated cubic boron nitride(111…
We propose a powerful method of controlling interaction between silicene and a substrate utilizing quantum size effect, which allows to grow silicene with tailored electronic properties. As an example we consider silicene on ultrathin Pb(111) layers, and demonstrate how the properties of silicene, including the binding energy, and the Dirac bands, can easily be tuned by quantum well states of the substrate. We also discover a novel mechanism of protecting the Dirac electrons from the influence of the substrate. This is associated with special arrangement of a part of Si atoms in silicene. Thes…
The deposition of one silicon monolayer on the silver (111) substrate in the temperature range 150-300$^\circ$C, gives rise to a mix of (4$\times$4), ($2\sqrt{3}\times 2\sqrt{3}$)R30$^\circ$ and ($\sqrt{13}\times\sqrt{13}$)R13.9$^\circ$ superstructures which strongly depends on the substrate temperature. We deduced from a detailed analysis of the LEED patterns and the STM images that all these superstructures are given by a quasi identical silicon single layer with a honeycomb structure (i.e. a silicene-like layer) with different rotations relatively to the silver substrate. The STM images mor…
By using first-principles calculations, we systematically investigated several observed phases of silicene on Ag(111) substrates and their electronic structures. We find that the original Dirac cone of silicene is about 1.5-1.7 eV deeply below the Fermi level and severely destroyed by the band hybridization between silicene and Ag in all the examined phases. Thus, silicene synthesized on Ag(111) substrates could not preserve its excellent electronic property and new method is needed to develop in synthesizing silicene with its Dirac cone surviving.
We performed a scanning tunneling microscopy and spectroscopy (STM/STS) study on the electronic structures of of root(3)Xroot(3)-silicene on Ag(111). We find that the coupling strength of root(3)Xroot(3)-silicene with Ag(111) substrate is variable at different regions, giving rise to notable effects in experiments. These evidences of decoupling or variable interaction of silicene with the substrate are helpful to in-depth understanding of the structure and electronic properties of silicene.
We study the structural and electronic properties of silicene on solid Ar(111) substrate using ab-initio calculations. We demonstrate that due to weak interaction quasi-freestanding silicene is realized in this system. The small binding energy of only $-32$ meV per Si atom also indicates the possibility to separate silicene from the solid Ar(111) substrate. In addition, a band gap of $11$ meV and a significant splitting of the energy levels due to spin-orbit coupling are observed.
Silicene, the two-dimensional allotrope of silicon, is predicted to exist in a low-buckled honeycomb lattice, characterized by semimetallic electronic bands with graphenelike energy-momentum dispersions around the Fermi level (represented by touching Dirac cones). Single layers of silicene are mostly synthesized by depositing silicon on top of silver, where, however, the different phases observed to date are so strongly hybridized with the substrate that not only the Dirac cones, but also the whole valence and conduction states of ideal silicene appear to be lost. Here, we provide evidence tha…
This concise book offers an essential introduction and reference guide for the many newcomers to the field of physics of elemental 2D materials. Silicene and related materials are currently among the most actively studied materials, especially following the first experimental synthesis on substrates in 2012. Accordingly, this primer introduces and reviews the most crucial developments regarding silicene from both theoretical and experimental perspectives. At the same time the reader is guided through the extensive body of relevant foundational literature. The text starts with a brief history o…
Silicene, analogous to graphene, is a one-atom-thick two-dimensional crystal of silicon which is expected to share many of the remarkable properties of graphene. The buckled honeycomb structure of silicene, along with its enhanced spin-orbit coupling, endows silicene with considerable advantages over graphene in that the spin-split states in silicene are tunable with external fields. Although the low-energy Dirac cone states lie at the heart of all novel quantum phenomena in a pristine sheet of silicene, the question of whether or not these key states can survive when silicene is grown or supp…
We investigate the band structure and topological phases of silicene embedded on halogenated Si(111) surface, by virtue of density functional theory and tight-binding calculations.Our results show that the Dirac character of low energy excitations in silicene is almost preserved in the presence of silicon substrate passivated by various halogens. Nevertheless, the combined effects of charge transfer into the substrate, stretching of bonds between silicon atoms, and symmetry breaking which originates from van der Waals interaction, result in a gap $E_{g1}$ in the spectrum of the embedded silice…
Two dimensional allotropes of group IV substrates including silicene, germanene and stanene have recently attracted considerable attention in nanodevice fabrication industry. These materials involving the buckled structure have been experimentally fabricated lately. In this study, first principles density functional theory calculations were utilized to investigate the mechanical properties of single layer and free standing silicene, germanene and stanene. Uniaxial tensile and compressive simulations were carried out to probe and compare stress strain properties; such as the Young modulus, Pois…
Since the discovery of graphene, intensive efforts have been made in search of novel two-dimensional (2D) materials. Decreasing the materials dimensionality to their ultimate thinness is a promising route to unveil new physical phenomena, and potentially improve the performance of devices. Among recent 2D materials, analogs of graphene, the group IV elements have attracted much attention for their unexpected and tunable physical properties. Depending on the growth conditions and substrates, several structures of silicene, germanene, and stanene can be formed. Here, we report the synthesis of a…
The origin of the large-scale stripe pattern of epitaxial silicene on the ZrB$_2$(0001) surface observed by scanning tunneling microscope experiments is revealed by first-principles calculations. Without stripes, the ($\sqrt{3}\times\sqrt{3}$)-reconstructed, one-atom-thick Si layer is found to exhibit a "zero-frequency" phonon instability at the $M$ point. In order to avoid a divergent response, the relevant phonon mode triggers the spontaneous formation of a new phase with a particular stripe pattern offering a way to lower both the atomic surface density and the total energy of silicene on t…
By using first-principles calculations, the electronic structure of planar and strained in-plane graphene/silicene heterostructure is studied. The heterostructure is found to be metallic in a strain range from -7% (compression) to +7% (tension). The effect of compressive/tensile strain on the chemical activity of the in-plane graphene/silicene heterostructure is examined by studying its interaction with the H2O molecule. It shows that compressive/tensile strain is able to increase the binding energy of H2O compared with the adsorption on a planar surface, and the charge transfer between the wa…
Silicene, a new two-dimensional (2D) material has attracted intense research because of the ubiquitous use of silicon in modern technology. However, producing free-standing silicene has proved to be a huge challenge. Until now, silicene could be synthesized only on metal surfaces where it naturally forms strong interactions with the metal substrate that modify its electronic properties. Here, we report the first experimental evidence of silicene sheet on an insulating NaCl thin film. This work represents a major breakthrough; for the study of the intrinsic properties of silicene, and by extens…
Recently, silicene, the graphene equivalent of silicon, has attracted a lot of attention due to its compatibility with Si-based electronics. So far, silicene has been epitaxy grown on various crystalline surfaces such as Ag(110), Ag(111), Ir(111), ZrB2(0001) and Au(110) substrates. Here, we present a new method to grow silicene via high temperature surface reconstruction of hexagonal IrSi3 nanocrystals. The h-IrSi3 nanocrystals are formed by annealing thin Ir layers on Si(111) surface. A detailed analysis of the STM images shows the formation of silicene like domains on the surface of some of …
Very recently we developed an efficient method to calculate the free energy of 2D materials on substrates and achieved high calculation precision for graphene or $γ$-graphyne on copper substrates. In the present work, the method was further confirmed to be accurate by molecular dynamic simulations of silicene on Ag substrate using empirical potential and was applied to predict the optimum conditions based on \emph{ab initio} calculations for silicene growth on Ag (110) and Ag (111) surface, which are in good agreement with previous experimental observations.
Epitaxial silicene, which is one single layer of silicon atoms packed in a honeycomb structure, demonstrates a strong interaction with the substrate that dramatically affects its electronic structure. The role of electronic coupling in the chemical reactivity between the silicene and the substrate is still unclear so far, which is of great importance for functionalization of silicene layers. Here, we report the reconstructions and hybridized electronic structures of epitaxial 4x4 silicene on Ag(111), which are revealed by scanning tunneling microscopy and angle-resolved photoemission spectrosc…
Density-functional theory calculations are used to verify the atomic structure of the $\sqrt{3}$$\times$$\sqrt{3}$ silicene phase grown on the Ag(111) surface. Recent experimental studies strongly suggested that the previous double-layer silicene model should be replaced with a Ag-mixed double-layer model resembling the top layers of the Ag/Si(111)-($\sqrt{3}$$\times$$\sqrt{3}$) surface. In our calculations, the Ag-mixed double-layer model is indeed energetically favored over the double-layer silicene model and well reproduces the reported scanning-tunneling microscopy and spectroscopy data. E…
Graphene, consisting of an inert, thermally stable material with an atomically flat, dangling bond-free surface is by essence an ideal template layer for van der Waals heteroepitaxy of two-dimensional materials such as silicene. However, depending on the synthesis method and growth parameters, graphene (Gr) substrates could exhibit, on a single sample, various surface structures, thicknesses, defects, and step heights. These structures noticeably affect the growth mode of epitaxial layers, e.g. turning the layer-by-layer growth into the Volmer-Weber growth promoted by defect-assisted nucleatio…
Graphane is graphene fully hydrogenated from both sides, forming a 1x1 structure, where all C atoms are in sp3 configuration. In silicene, the Si atoms are in a mix-sp2/sp3 configuration, it is therefore natural to imagine silicane in analogue to graphane. However, monoatomic silicene sheet grown on substrates generally reconstructs into different phases, and only partially hydrogenated silicene with reconstructions had been reported before. In this report we produce half-silicane, where one Si sublattice is fully H-saturated and the other sublattice is intact, forming a perfect 1x1 structure.…
Silicene and germanene derivatives constructed from periodic dumbbell units play a crucial role in multilayers of these honeycomb structures. Using first-principles calculations based on density functional theory, here we investigate the dumbbell formation mechanisms and energetics of Group IV atoms adsorbed on graphene, silicene, germanene and stanene monolayer honeycomb structures. The stabilities of the binding structures are further confirmed by performing ab-initio molecular dynamics calculations at elevated temperatures, except for stanene which is subject to structural instability upon …
Free standing silicene is predicted to display comparable electronic properties as graphene. However, the yet synthesized silicene-like structures have been only realized on different substrates which turned out to exhibit versatile crystallographic structures that are very different from the theoretically predicted buckled phase of freestanding silicene. This calls for a different approach where silicene is stabilized using very weakly interacting surfaces. We propose here a novel route by using graphene bilayer as a scaffold. The confinement between the flat graphene layers results in a plan…
By the generalized gradient approximation in framewok of density functional theory, we investigate a 2D topological insulator of new silicon allotrope (call dumbbell silicene synthesized recently by Cahangirov et al) through tuning external compression strain, and find a topological quantum phase transition from normal to topological insulator, i.e., the dumbbell silicene can turn a two-dimensional topological insulator with an inverted band gap. The obtained maximum topological nontrivial band gap about 12 meV under isotropic strain is much larger than that for previous silicene, and can be f…
Using a gold (111) surface as a substrate we have grown in situ by molecular beam epitaxy an atom-thin, ordered, two-dimensional multi-phase film. Its growth bears strong similarity with the formation of silicene layers on silver (111) templates. One of the phases, forming large domains, as observed in Scanning Tunneling Microscopy, shows a clear, nearly flat, honeycomb structure. Thanks to thorough synchrotron radiation core-level spectroscopy measurements and advanced Density Functional Theory calculations we can identify it to a $\sqrt{3}$x$\sqrt{3}$R(30°) germanene layer in coincidence wit…
We study silicene on hexagonal boron nitride, using first principles calculations. Since hexagonal boron nitride is semiconducting, the interaction with silicene is weaker than for metallic substrates. It therefore is possible to open a 50 meV band gap in the silicene. We further address the effect of Mn decoration by determining the onsite Hubbard interaction parameter, which turns out to differ significantly for decoration at the top and hollow sites. The induced magnetism in the system is analyzed in detail.
We report first-principles calculations that clarify stability and electronic structures of silicene on Ag(111) surfaces. We find that several stable structures exist for silicene/Ag(111), exhibiting a variety of images of scanning tunneling microscopy. We also find that Dirac electrons are {\em absent} near Fermi energy in all the stable structures due to buckling of the Si monolayer and mixing between Si and Ag orbitals. We instead propose that either BN substrate or hydrogen processing of Si surface is a good candidate to preserve Dirac electrons in silicene.
Highly oriented pyrolitic graphite (HOPG) is an inert substrate with a structural honeycomb lattice, well suited for the growth of two-dimensional (2D) silicene layer. It was reported that when Si atoms are deposited on HOPG surface at room temperature, they arrange in two configurations: silicene nanosheets and three dimensional clusters. In this work we demonstrate, by using scanning tunneling microscopy (STM) and Raman spectroscopy, that a third configuration stabilizes in the form of Si 2D nanosheets intercalated below the first top layer of carbon atoms. The Raman spectra reveal a structu…
So far, it represents a challenging task to reproduce angle-resolved photoelectron (ARPES) spectra of epitaxial silicene by first-principles calculations. Here, we report on the resolution of the previously controversial issue related to the structural configuration of silicene on the ZrB$_2$(0001) surface and its band structure. In particular, by representing the band structure in a large Brillouin zone associated with a single Si atom, it is found that the imaginary part of the one-particle Green's function follows the spectral weight observed in ARPES spectra. By additionally varying the in…
Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice. We investigate the topological properties of a silicene superstructure generated by an external periodic potential. The superstructure is a quantum spin-Hall (QSH) insulator if it is topologically connected to silicene. It is remarkable that two inequivalent K and K' points in the silicene Brillouin zone are identified in certain superstructures. In such a case two Dirac cones coexist at the same Dirac point in the momentum space and they are hexagonally warped by the Coulomb interaction. We carry out a numer…
The discovery of intriguing properties related to the Dirac states in graphene has spurred huge interest in exploring its two-dimensional group-IV counterparts, such as silicene, germanene, and stanene. However, these materials have to be obtained via synthesizing on substrates with strong interfacial interactions, which usually destroy their intrinsic $π$($p_z$)-orbital Dirac states. Here we report a theoretical study on the existence of Dirac states arising from the $p_{x,y}$ orbitals instead of $p_z$ orbitals in silicene on 4H-SiC(0001), which survive in spite of the strong interfacial inte…
The plasmonic character of monolayer silicene is investigated by time-dependent density functional theory in the random phase approximation. The energy-loss function of the system is analyzed, with particular reference to its induced charge-density fluctuations, i.e., plasmon resonances and corresponding dispersions, occurring in the investigated energy-momentum region. At energies larger than 1.5eV, two intrinsic interband modes are detected and characterized. The first one is a hybridized pi-like plasmon, which is assisted by competing one-electron processes involving sp2 and sp3 states. The…
The coupling between the electrical transport properties of La2/3Sr1/3MnO3 (LSMO) thin films and structural phase transitions of SrTiO3 (STO) substrates at Ts = 105 K has been investigated. We found that the electrical resistivity of LSMO films exhibit a cusp at Ts, which is greatly amplified by tuning films to the verge of metallic and insulating phases, i.e., to the boundary of two delicate competing electronic states. Our results demonstrate that small amounts of strain can tip the subtle balance of competing interactions and tune the electronic properties in correlated electron materials.
Strain engineering of functional properties in epitaxial thin films of strongly correlated oxides exhibiting octahedral-framework structures is hindered by the lack of adequate misfit relaxation models. Here we present unreported experimental evidences of a four-stage hierarchical development of octahedral-framework perturbations resulting from a progressive imbalance between electronic, elastic and octahedral tilting energies in La0.7Sr0.3MnO3 epitaxial thin films grown on SrTiO3 substrates. Electronic softening of the Mn - O bonds near the substrate leads to the formation of an interfacial l…
We study a system of particles in two dimensions interacting via a dipolar long-range potential $D/r^3$ and subject to a square-lattice substrate potential $V({\bf r})$ with amplitude $V$ and lattice constant $b$. The isotropic interaction favors a hexagonal arrangement of the particles with lattice constant $a$, which competes against the square symmetry of the substrate lattice. We determine the minimal-energy states at fixed external pressure $p$ generating the commensurate density $n = 1/b^2 = (4/3)^{1/2}/a^2$ in the absence of thermal and quantum fluctuations, using both analytical and nu…
Our first-principles results show that geometric frustration can be induced in thin films of multiferroic BiFeO3. We find that competing magnetic interactions occur in the so-called super-tetragonal phase of this material, which can be grown on strongly-compressive substrates. We show that the frustration level can be tuned by appropriately choosing the substrate; in fact, the three-dimensional spin order gets totally annihilated in a narrow range of epitaxial strains. We argue that the effects revealed here are not exclusive to BiFeO3, and predict that they also occur in multiferroic BiCoO3.
We experimentally study the surface roughness and the lateral friction force in single-layer MoS2 crystals deposited on different substrates: SiO2, mica and hexagonal boron nitride (h-BN). Roughness and sliding friction measurements are performed by atomic force microscopy (AFM). We find a strong dependence of the MoS2 roughness on the underlying substrate material, being h-BN the substrate which better preserves the flatness of the MoS2 crystal. The lateral friction also lowers as the roughness decreases, and attains its lowest value for MoS2 flakes on h-BN substrates. However, it is still hi…
We demonstrate the engineering of a source of radiation from growing surface plasmons (charge density oscillations) in a composite nano-system. The considered hybrid nano-structure consists of a thick layer of a conducting substrate on whose surface a plasmon mode is activated conjoining a single or pair of thin sheets of either monolayer graphene, silicene or a two-dimensional electron gas as would occur at a hetero-interface. When an electric current is passed through either a layer or within the substrate, the low-frequency plasmons in the layer may bifurcate into separate streams due to th…
We study the dipole layer formed at metal-organic interfaces by means of first-principles calculations. Interface dipoles are monitored by calculating the work function change of Au, Ag, Al, Mg and Ca surfaces upon adsorption of a monolayer of PTCDA (3,4,9,10-perylene-tetra-carboxylic-di-anhydride), perylene or benzene molecules. Adsorption of PTCDA leads to pinning of the work function for a range of metal substrates. It gives interface dipoles that compensate for the difference in the clean metal work functions, leading to a nearly constant work function. In contrast, adsorption of benzene a…
The films of FeSe on substrates have attracted attention because of their unusually high-temperature (Tc) superconducting properties whose origins continue to be debated. To disentangle the competing effects of the substrate and interlayer and intralayer processes, we present here results of density functional theory (DFT)-based analysis of the electronic structure of unsupported FeSe films consisting of 1 to 5 layers (1L-5L). Furthermore, by solving the Bardeen-Schrieffer-Cooper (BCS) equation with spin-wave exchange attraction derived from the Hubbard model, we find the superconducting criti…
A simple model was constructed to describe the polar ordering of non-centrosymmetric supramolecular aggregates formed by self assembling triblock rodcoil polymers. The aggregates are modeled as dipoles in a lattice with an Ising-like penalty associated with reversing the orientation of nearest neighbor dipoles. The choice of the potentials is based on experimental results and structural features of the supramolecular objects. For films of finite thickness, we find a periodic structure along an arbitrary direction perpendicular to the substrate normal, where the repeat unit is composed of two e…
The sequence of ground states for SrTiO3 film subjected to epitaxial strain as well as to mechanical stress along the [001] and [110] axes is calculated from first principles within the density functional theory. Under the fixed-strain boundary conditions, an increase in the lattice parameter of a substrate results in the $I4cm \to I4/mcm \to Ima2 \to Cm \to Fmm2 \to Ima2$(II) sequence of ground states. Under the fixed-stress boundary conditions, the phase sequence is different and depends on how the stress is applied. It is revealed that the simultaneous presence of competing ferroelectric an…
In the present work, we study morphologies arising due to competing substrate interaction, electric field and confinement effects on a symmetric diblock copolymer. We employ a coarse grained non-local Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric field-substrate strength space for differ…
Silicon carbide (SiC) is an excellent substrate for growth and manipulation of large scale, high quality epitaxial graphene. On the carbon face (the ($\bar{1}\bar{1}\bar{1}$) or $(000\bar{1}$) face, depending on the polytype), the onset of graphene growth is intertwined with the formation of several competing surface phases, among them a (3$\times$3) precursor phase suspected to hinder the onset of controlled, near-equilibrium growth of graphene. Despite more than two decades of research, the precise atomic structure of this phase is still unclear. We present a new model of the (3$\times$3)-Si…
Positional and Rotational Molecular Degrees of Freedom in a Metal-Organic Surface Alloy: the Copper-Fullerene System and its Multiple Structural Phases
The magnetic structure of a Cr monolayer on a W(110) substrate is investigated by means of first-principles calculations based on the noncollinear spin density functional theory (DFT). As magnetic ground state we find a long-period homochiral left-rotating spin spiral on-top of an atomic-scale anti-ferromagnetic order of nearest neighbor atoms. The rotation angle of the magnetic moment changes inhomogeneously from atom to atom across the spiral. We predict a propagation direction along the crystallographic [001] direction with a period length of 14.3 nm, which is in excellent agreement with a …
Electronic, magnetic, and transport properties of the antiferromagnetic (AFM) CuMnAs alloy with tetragonal structure, promising for the AFM spintronics, are studied from first principles using the Vienna ab-initio simulation package. We investigate the site-occupation of sublattices and the lattice parameters of three competing phases. We analyze the factors that determine which of the three conceivable structures will prevail. We then estimate formation energies of possible defects for the experimentally prepared lattice structure. Mn$_{\rm Cu}$- and Cu$_{\rm Mn}$-antisites as well as Mn$\lef…
Competing Constraints on Superconductivity in Thick FeSe films
Materials Genome Institute, Shanghai University（上海大学材料基因组研究院）；College of Ocean Science and Engineering, Shanghai Maritime University（上海海事大学海洋科学与工程学院）；Department of Physics and Shanghai Key Laboratory for High Temperature Superconductors, Shanghai University（上海大学物理系及高温超导上海市重点实验室）；Institute for Quantum Science and Technology, Shanghai University（上海大学量子科学与技术研究院）
Phase separated perovskite manganites have competing phases with different crystal structures, magnetic and electronic properties. Hence, strain effects play a critical role in determining the magnetic properties of manganite thin films. Here we report the effect of anisotropic stress on the magnetic properties of the phase separated manganite (La$_{0.4}$Pr$_{0.6}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$. Thin films of (La$_{0.4}$Pr$_{0.6}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$ grown under anisotropic in-plane stress on (110) NdGaO$_{3}$ substrates display in-plane mangetic anisotropy and single domain to multi…
