Results for "Claudia Felser"

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The half-metallic ferromagnet Co2Mn0.5Fe0.5SiJul 13 2006Electronic structure calculation were used to predict a new material for spintronic applications. Co2Mn0.5Fe0.5Si is one example which is stable against on-site correlation and disorder effects due to the position of the Fermi energy in the middle of ... More
Disorder-induced cubic phase in Fe$_2$-based Heusler alloysFeb 04 2013Based on first-principles electronic structure calculations, we analyze the chemical and magnetic mechanisms stabilizing the cubic phase in Fe$_2$-based Heusler materials, which were previously predicted to be tetragonal when being chemically ordered. ... More
Topological Materials: Weyl SemimetalsNov 13 2016Topological insulators and topological semimetals are both new classes of quantum materials, which are characterized by surface states induced by the topology of the bulk band structure. Topological Dirac or Weyl semimetals show linear dispersion round ... More
Non-collinear Antiferromagnets and the Anomalous Hall EffectOct 22 2014The anomalous Hall effect is investigated theoretically by means of density functional calculations for the non-collinear antiferromagnetic order of the hexagonal compounds Mn$_3$Ge and Mn$_3$Sn using various planar triangular magnetic configurations ... More
Weyl Fermions in antiferromagnetic Mn(3)Sn and Mn(3)GeNov 10 2017Jan 04 2018The anomalous Hall effect in the noncollinear antiferromagnetic metals Mn(3)Ge and Mn(3)Sn has been observed after a theoretical prediction made by us (EPL, 108, 67001 (2014)). The experimental values of the anomalous Hall conductivities (AHC) are large ... More
Magnetically Switchable Light-Matter Interaction in the Two-Dimensional Magnet CrI3Mar 14 2019Aug 14 2019Coupling different physical properties is a fascinating subject of physics. Already well-known are the multiferroics which show properties of ferroelectrics and magnets. But ferroelectricity by itself also entails the bulk photovoltaic effect, a light-matter ... More
Berry-curvatures and anomalous Hall effect in Heusler compoundsOct 13 2011Berry curvatures are computed for a set of Heusler compounds using density functional (DF) calculations and the wave functions that DF provide. The anomalous Hall conductivity is obtained from the Berry curvatures. It is compared with experimental values ... More
Giant magnetoresistance and extraordinary magnetoresistance in inhomogeneous semiconducting DyNiBiSep 26 2007Oct 16 2008The semiconducting half-Heulser compound DyNiBi shows a negative giant magnetoresistance (GMR) below 200 K. Except for a weak deviation, this magnetoresistance scales roughly with the square of the magnetization in the paramagnetic state, and is related ... More
Topological Materials: Weyl SemimetalsNov 13 2016Nov 21 2016Topological insulators and topological semimetals are both new classes of quantum materials, which are characterized by surface states induced by the topology of the bulk band structure. Topological Dirac or Weyl semimetals show linear dispersion round ... More
Properties of the quaternary half-metal-type Heusler alloy Co$_2$Mn$_{1-x}$Fe$_x$SiJun 05 2006Aug 10 2006This work reports on the bulk properties of the quaternary Heusler alloy Co$_2$Mn$_{1-x}$Fe$_x$Si with the Fe concentration $x=$. All samples, which were prepared by arc melting, exhibit $L2_1$ long range order over the complete range of Fe concentration. ... More
High energy, high resolution photoelectron spectroscopy of Co2Mn(1-x)Fe(x)SiNov 05 2006This work reports on high resolution photoelectron spectroscopy for the valence band of Co2Mn(1-x)Fe(x)Si (x=0,0.5,1) excited by photons of about 8 keV energy. The measurements show a good agreement to calculations of the electronic structure using the ... More
Anisotropic Topological Hall Effect with Real and Momentum Space Berry Curvature in the Antiskrymion Hosting Heusler Compound Mn$_{1.4}$PtSnMar 28 2019The topological Hall effect (THE) is one of the key signatures of topologically non-trivial magnetic spin textures, wherein electrons feel an additional transverse voltage to the applied current. The magnitude of THE is often small compared to the anomalous ... More
Unusual magneto-transport from Si-square nets in topological semimetal HfSiSDec 15 2016The class of topological semimetals comprises a large pool of compounds. Together they provide a wide platform to realize exotic quasiparticles for example Dirac, nodal line Dirac and Weyl fermions. In this letter, we report the Berry phase, Fermi surface ... More
New Family of Quantum Spin Hall Insulators in Two-dimensional Transition-Metal Halide with Large Nontrivial Band GapsOct 21 2015Dec 14 2015Topological insulators (TIs) are promising for achieving dissipationless transport devices due to the robust gapless states inside the insulating bulk gap. However, currently realized 2D TIs, quantum spin Hall (QSH) insulators, suffer from ultra-high ... More
Graphene-based topological insulator with an intrinsic bulk band gap above room temperatureOct 09 2013Topological insulators (TIs) represent a new quantum state of matter characterized by robust gapless states inside the insulating bulk gap. The metallic edge states of a two-dimensional (2D) TI, known as quantum spin Hall (QSH) effect, are immune to backscattering ... More
Ab initio study of topological surface states of strained HgTeApr 24 2014The topological surface states of mercury telluride (HgTe) are studied by ab initio calculations assuming different strains and surface terminations. For the Te-terminated surface, a single Dirac cone exists at the $\Gamma$ point. The Dirac point shifts ... More
Topological surface states of Bi2Se3 with the coexistence of Se vacanciesSep 26 2012Oct 09 2012Although topological surface states are known to be robust against non-magnetic surface perturbations, their band dispersions and spatial distributions are still sensitive to the surface defects. Take Bi2Se3 as an example, we demonstrated that Se vacancies ... More
Graphene-like Dirac states and Quantum Spin Hall Insulators in the square-octagonal MX2 (M=Mo, W; X=S, Se, Te) IsomersMar 29 2015We studied the square-octagonal lattice of the transition metal dichalcogenide MX$_2$ (with $M$=Mo, W; $X$=S, Se and Te), as an isomer of the normal hexagonal compound of MX$_2$. By band structure calculations, we observe the graphene-like Dirac band ... More
Evidence for an axionic charge density wave in the Weyl semimetal (TaSe4)2IJun 11 2019An axion insulator is a correlated topological phase, predicted to arise from the formation of a charge density wave in a Weyl semimetal. The accompanying sliding mode in the charge density wave phase, the phason, is an axion. It is expected to cause ... More
On the superconductivity of TiNCl and ZrNCl: A local bonding perspectiveAug 13 2014We analyze the superconductors TiNCl and ZrNCl from a local bonding perspective. Although TiNCl crystallizes in an orthorhombic structure and ZrNCl crystallizes in a hexagonal structure, both compounds show significant structural similarities, for example ... More
Discovery of Magnetic Antiskyrmions Beyond Room Temperature in Tetragonal Heusler MaterialsMar 03 2017Skyrmions, topologically stable spin textures, are of great interest for new generations of spintronic devices. In general, the stabilization of skyrmions has been achieved in systems with broken inversion symmetry, where the asymmetric Dzyaloshinskii-Moriya ... More
Prediction of weak topological insulators in layered semiconductorsJun 20 2012We report the discovery of weak topological insulators by ab initio calculations in a honeycomb lattice. We propose a structure with an odd number of layers in the primitive unit-cell as a prerequisite for forming weak topological insulators. Here, the ... More
The role of correlations in the high-pressure phase of FeSeNov 03 2010We present a systematic study of the high-pressure FeSe phase performed by means of the first-principle electronic structure calculations. Basing on available experimental information about the unit cell geometry we calculate the band structure and characterize ... More
Covalent bonding and the nature of band gaps in some half-Heusler compoundsSep 18 2005Half-Heusler compounds \textit{XYZ}, also called semi-Heusler compounds, crystallize in the MgAgAs structure, in the space group $F\bar43m$. We report a systematic examination of band gaps and the nature (covalent or ionic) of bonding in semiconducting ... More
Large anomalous Hall and Nernst effect from nodal line symmetry breaking in Fe$_2$MnX (X=P,As,Sb)Nov 12 2018A large Berry curvature in the vicinity of the Fermi energy is required in order to obtain a large anomalous Hall and Nernst effect. This Berry curvature can be induced by Weyl points and gapped nodal lines. One of the possible mechanisms takes place ... More
A p-type Heusler compound: Growth, structure, and properties of epitaxial thin NiYBi films on MgO(100)Sep 25 2012Epitaxial semiconducting NiYBi thin films were directly prepared on MgO(100) substrates by magnetron sputtering. The intensity ratio of the (200) and (400) diffraction peaks, I(200)/I(400) = 2.93, was close to the theoretical value (3.03). The electronic ... More
Crystal structure, magnetism, and bonding of the hexagonal compounds Pd$_{1.63}$Mn$_{0.37}$Si and Pd$_{1.82}$Mn$_{0.18}$Ge related to the Fe$_2$P structureMar 09 2007We have used single crystal X-ray diffraction methods to establish the crystal structures of a compound in the Pd-Mn-Si system and in the Pd-Mn-Ge system. The title compounds have structures related to the Fe$_2$P structure type and are ferromagnetic ... More
A large energy-gap oxide topological insulator based on the superconductor BaBiO3Aug 10 2013Mixed-valent perovskite oxides based on BaBiO3 (BBO) are, like cuperates, well-known high-Tc superconductors. Recent ab inito calculations have assigned the high-Tc superconductivity to a correlation-enhanced electron--phonon coupling mechanism, stimulating ... More
Prediction of Ideal Triple Degenerate Points in HfIrAs and HfIrBiAug 03 2018In this study, two ideal triple degenerate point (TDP) semimetals were predicted, namely, HfIrAs and HfIrBi, that exhibit clean TDPs around the fermi level. At the atomic level, the origin of the TDP was analyzed, and when combined with the low-energy ... More
Behavior of $\mathbf{Σ3}$ grain boundaries in \CISe\ and \CGSe\ photovoltaic absorbers as revealed by first-principles hybrid functional calculationsJun 30 2015Jan 06 2016The inconclusive results of the previous first-principles studies on the \S3 \ grain boundaries (GBs) in \CISe\ reveal the importance of employing a method that can correctly describe the electronic structure of this solar-cell material. We have employed ... More
Calculated electronic and magnetic properties of the half-metallic, transition metal based Heusler compoundsNov 07 2006In this work, results of {\it ab-initio} band structure calculations for $A_2BC$ Heusler compounds that have $A$ and $B$ sites occupied by transition metals and $C$ by a main group element are presented. This class of materials includes some interesting ... More
Topological phase transitions in bulkSep 27 2012We consider the analogy between the topological phase transition which occurs as a function of spatial coordinate on a surface of a non-trivial insulator, and the one which occurs in the bulk due to the change of internal parameters (such as crystal field ... More
Giant intrinsic spin Hall effect in the TaAs family of Weyl semimetalsApr 25 2016Aug 12 2016Since their discovery, topological insulators have been expected to be ideal spintronic materials owing to the spin currents carried by surface states with spin--momentum locking. However, the bulk doping problem remains an obstacle that hinders such ... More
Topological Contributions to the Anomalous Nernst and Hall Effect in the Chiral Double-Helimagnetic SystemMay 08 2018MnP and FeP are show complex magnetic spiral states with geometric phase contributions to the anomalous Hall effect and the topological Hall effect, where both have thermoelectric Nernst counterparts. We use state of the art first principle calculations ... More
Planar Hall effect in the Weyl semimetal GdPtBiNov 11 2017Jul 26 2018Observation of Weyl and Dirac Fermions in condensed matter systems is one of the most important discoveries. Among the very few available tools to characterize Weyl semimetals through electrical transport, negative magnetoresistance is most commonly used. ... More
Magnetic field induced strong valley polarization in the three dimensional topological semimetal LaBiMar 07 2017Oct 03 2017LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high ... More
Long-term stability of phase-separated Half-Heusler compoundsFeb 06 2015Half-Heusler (HH) compounds have shown high Figure of merits up to 1.5. The key to these high thermoelectric efficiencies is an intrinsic phase separation, which occurs in multicomponent Half-Heusler compounds and leads to an significantly reduction of ... More
Observation and manipulation of maximal Chern numbers in the chiral topological semimetal PdGaJul 19 2019Topological semimetals feature protected nodal band degeneracies characterized by a topological invariant known as the Chern number. The magnitude and sign of this invariant determine many of the exotic properties of such semimetals, including the number ... More
Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn$_{\text{3}}$SnMay 31 2019Harnessing the unique properties of non-collinear antiferromagnets (AFMs) will be essential for exploiting the full potential of antiferromagnetic spintronics. Indeed, many of the effects enabling ferromagnetic spintronic devices have a corresponding ... More
Actinide Topological Insulator Materials with Strong InteractionNov 04 2011Topological band insulators have recently been discovered in spin-orbit coupled two and three dimensional systems. In this work, we theoretically predict a class of topological Mott insulators where interaction effects play a dominant role. In actinide ... More
A new diluted magnetic semiconductor: The half-metallic ferromagnet CoTi(1-x)FexSbSep 02 2006Half-Heusler compounds with 18 valence electrons are semi-conducting. It will be shown that doping with electrons results in half-metallic ferromagnets, similar to the case of diluted semi-conductors. CoTiSb is known to be a semi-conducting Half-Heusler ... More
Guidelines for understanding cubic manganese-rich Heusler compoundsSep 23 2014Manganese-rich Heusler compounds are attracting much interest in the context of spin transfer torque and rare-earth free hard magnets. Here we give a comprehensive overview of the magnetic properties of non-centrosymmetric cubic Mn$_2$-based Heusler materials, ... More
Heusler, Weyl, and BerryFeb 11 2018Heusler materials, initially discovered by Fritz Heusler more than a century ago, have grown into a family of more than 1000 compounds, synthesized from combinations of more than 40 elements. These materials show a wide range of properties, but new properties ... More
Orbital ordering of Ir-t2g states in the double perovskite Sr2CeIrO6Jul 30 2015The electronic and magnetic properties of monoclinic double perovskite Sr$_2$CeIrO$_6$ were examined based on both experiments and first-principles density functional theory calculations. From the calculations we conclude that low-spin-state Ir$^{4+}$ ... More
Hidden type-II Weyl points in the Weyl semimetal NbPAug 23 2017As one of Weyl semimetals discovered recently, NbP exhibits two groups of Weyl points with one group lying inside the $k_z=0$ plane and the other group staying away from this plane. All Weyl points have been assumed to be type-I, for which the Fermi surface ... More
Correlation in the transition metal based Heusler compounds Co$_2$MnSi and Co$_2$FeSiJan 30 2006Half-metallic ferromagnets like the full Heusler compounds with formula X$_2$YZ are supposed to show an integer value of the spin magnetic moment. Calculations reveal in certain cases of X = Co based compounds non-integer values, in contrast to experiments. ... More
Lone Pair Effect, Structural Distortions and Potential for Superconductivity in Tl PerovskitesFeb 07 2013Drawing the analogy to BaBiO3, we investigate via ab-initio electronic structure calculations potential new superconductors of the type ATlX3 with A = Rb, Cs and X = F, Cl, and Br, with a particular emphasis on RbTlCl3. Based on chemical reasoning, supported ... More
Electrically tuneable nonlinear anomalous Hall effect in two-dimensional transition-metal dichalcogenides WTe2 and MoTe2Apr 30 2018We studied the nonlinear electric response in WTe2 and MoTe2 monolayers. When the inversion symmetry is breaking but the the time-reversal symmetry is preserved, a second-order Hall effect called the nonlinear anomalous Hall effect (NLAHE) emerges owing ... More
Magnetism in tetragonal manganese-rich Heusler compoundsJun 11 2015A comprehensive study of the total energy of manganese-rich Heusler compounds using density functional theory is presented. Starting from a large set of cubic parent systems, the response to tetragonal distortions is studied in detail. We single out the ... More
Comparison of two structures for transition-metal-based half Heusler alloys exhibiting fully compensated half metallicityAug 18 2011We search for new fully compensated half metals, in which only one electronic spin channel is conducting and there exists no net magnetic moment. We focus on half Heusler alloys and we examine the physical consequence of different crystal structures found ... More
Topological insulators and thermoelectric materialsSep 26 2012Nov 30 2012Topological insulators (TIs) are a new quantum state of matter which have gapless surface states inside the bulk energy gap. Starting with the discovery of two dimensional TIs, the HgTe-based quantum wells, many new topological materials have been theoretically ... More
Na4IrO4: Square-Planar Coordination of a Transition Metal in d5 Configuration due to Weak On-Site Coulomb InteractionsFeb 08 2015Mar 20 2015Local environments and valence electron counts primarily determine the electronic states and physical properties of transition metal complexes. For example, square-planar surroundings found in transition oxometalates such as curprates are usually associated ... More
Realization of quantum anomalous Hall effect from a magnetic Weyl semimetalDec 21 2017Jan 26 2018The quantum anomalous Hall effect (QAHE) and magnetic Weyl semimetals (WSMs) are topological states induced by intrinsic magnetic moments and spin-orbital coupling. Their similarity suggests the possibility of achieving the QAHE by dimensional confinement ... More
Spin-polarized current in non-collinear antiferromagnetsFeb 01 2017Sep 28 2018Noncollinear antiferromagnets, such as Mn$_3$Sn and Mn$_3$Ir, were recently shown to be analogous to ferromagnets in that they have a large anomalous Hall effect. Here we show that these materials are similar to ferromagnets in another aspect: the charge ... More
Realization of spin gapless semiconductors: the Heusler compound Mn2CoAlSep 29 2012Recent studies have reported an interesting class of semiconductor materials that bridge the gap between semiconductors and halfmetallic ferromagnets. These materials, called spin gapless semiconductors, exhibit a bandgap in one of the spin channels and ... More
Kinetic arrest related to a first-order ferrimagnetic to antiferromagnetic transition in the Heusler compound Mn2PtGaApr 16 2013We report a magnetization study of the Heusler compound Mn2PtGa that shows the existence of a magnetic-glass state. Mn2PtGa shows a first-order ferromagnetic (FM)/ferrimagnetic (FI) to antiferromagnetic (AFM) transition in contrast to the martensitic ... More
Surface and bulk properties of the Heusler compound Co2Cr0.6Fe0.4Al: a Moessbauer studyOct 17 2006To explore its structural and magnetic properties, the Heusler compound Co2Cr0.6Fe0.4Al was investigated using Moessbauer spectroscopy. The results of both transmission and conversion electron Moessbauer spectroscopy (CEMS) are analyzed to obtain insight ... More
Ab-inito study of low temperature magnetic properties of double perovskite Sr2FeOsO6Mar 19 2014Using density-functional theory calculations, we investigated the electronic structure and magnetic exchange interactions of the ordered 3d-5d double perovskite Sr2FeOsO6, which has recently drawn attention for interesting antiferromagnetic transitions. ... More
Characterization of topological band structures away from the Fermi level by anomalous Nernst measurementsJul 20 2018Resolving the structure of energy bands in transport experiments is a major challenge in condensed matter physics and material science. Sometimes, however, traditional electrical conductance or resistance measurements only provide very small signals, ... More
Strong anomalous Nernst effect in collinear magnetic Weyl semimetals without net magnetic momentsMar 09 2018Mar 26 2018We predict a large anomalous Nernst effect in the inverse Heusler compensated ferrimagnets Ti$_2$Mn$X$ ($X$=Al,Ga,In) with vanishing net magnetic moments. Though the net magnetic moment is zero, the Weyl points in these systems lead to a large anomalous ... More
Topological Weyl semimetals in $\rm Bi$$_{1-x}$$\rm Sb$$_{x}$ alloysFeb 01 2018We have investigated the Weyl semimetal (WSM) phases in bismuth antimony ($\rm Bi$$_{1-x}$$\rm Sb$$_{x}$) alloys by the combination of atomic composition and arrangement. Via first principles calculations, we have found two WSM states with the Sb concentration ... More
Active role of the nonmagnetic cations in magnetic interactions for the double-perovskite Sr2BOsO6 (B=Y, In, Sc)May 02 2016Using first-principles density functional theory, we have investigated the electronic and magnetic properties of recently synthesized and characterized 5d double-perovskites Sr2BOsO6 (B=Y, In, Sc). The electronic structure calculations show that in all ... More
Electronic and crystalline structures of zero band-gap PdLuBi thin films grown epitaxially on MgO(100)Sep 25 2012Thin films of the proposed topological insulator PdLuBi - a Heusler compound with the C1b structure - were prepared on Ta-Mo-buffered MgO(100) substrates by co-sputtering from PdBi2 and Lu targets. Epitaxial growth of high-quality PdLuBi films was confirmed ... More
Experimental signatures of the mixed axial-gravitational anomaly in the Weyl semimetal NbPMar 29 2017Weyl semimetals are materials where electrons behave effectively as a kind of massless relativistic particles known asWeyl fermions. These particles occur in two flavours, or chiralities, and are subject to quantum anomalies, the breaking of a conservation ... More
New Family of Robust 2D Topological Insulators in van der Waals HeterostructuresJun 12 2014We predict a new family of robust two-dimensional (2D) topological insulators in van der Waals heterostructures comprising graphene and chalcogenides BiTeX (X=Cl, Br and I). The layered structures of both constituent materials produce a naturally smooth ... More
Spin Texture and Mirror Chern number in Hg-Based ChalcogenidesApr 28 2014May 03 2014The unique feature of surface states in topological insulators is the so-called "spin-momentum locking", which means that electron spin is oriented along a fixed direction for a given momentum and forms a texture in the momentum space. In this work, we ... More
Large linear magnetoresistance and weak anti-localization in Y(Lu)PtBi topological insulatorsFeb 02 2015Feb 03 2015Topological insulators are new kind of Dirac materials that possess bulk insulating and surface conducting behavior. They are basically known for their unique electronic properties at the surface. Here we present the magneto-transport properties of our ... More
Exchange bias up to room temperature in the antiferromagnetic bulk hexagonal Mn3GeNov 13 2013This work reports an exchange bias (EB) effect up to room temperature in the binary intermetallic bulk compound Mn3.04Ge0.96. The sample annealed at 700 K crystallizes in a tetragonal structure with ferromagnetic ordering, whereas, the sample annealed ... More
Paramagnetic to ferromagnetic phase transition in lightly Fe-doped Cr$_2$BJun 17 2014Cr$_2$B displays temperature independent paramagnetism. We induce ferromagnetism by replacing less than $3\,\%$ of the Cr atoms by Fe. By the lowest Fe doping level made, Curie-Weiss behavior is observed; $\Theta_{CW}$ changes from $-20\,$K for $0.5\,\%$ ... More
Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compoundsOct 30 2007The XYZ half-Heusler crystal structure can conveniently be described as a tetrahedral zinc blende YZ structure which is stuffed by a slightly ionic X species. This description is well suited to understand the electronic structure of semiconducting 8-electron ... More
High thermoelectric figure of merit in p-type Half-Heuslers by intrinsic phase separationFeb 11 2015Improvements in the thermoelectric properties of Half-Heusler materials have been achieved by means of a micrometer-scale phase separation that increases the phonon scattering and reduces the lattice thermal conductivity. A detailed study of the p-type ... More
Synthesis, Crystal Structure and Physical Properties of Sr2FeOsO6Jul 09 2013In the exploration of new osmium based double perovskites, Sr2FeOsO6 is a new insertion in the existing family. The polycrystalline compound has been prepared by solid state synthesis from the respective binary oxides. PXRD analysis shows the structure ... More
Quantum Anomalous Hall Effect in Magnetic Insulator HeterostructureNov 06 2014Nov 12 2014Based on ab initio calculations, we predict that a monolayer of Cr-doped (Bi,Sb)2Te3 and GdI2 heterostructure is a quantum anomalous Hall insulator with a non-trivial band gap up to 38 meV. The principle behind our prediction is that the band inversion ... More
Topological phase transition induced by random substitutionJul 14 2012The transition from topologically nontrivial to a trivial state is studied by first-principles calculations on bulk zinc-blende type (Hg$_{1-x}$Zn$_x$)(Te$_{1-x}$S$_x$) disordered alloy series. The random chemical disorder was treated by means of the ... More
Strong spin-Hall and Nernst effects in a p-band semimetalMay 30 2018Since spin currents can be generated, detected, and manipulated via the spin Hall effect (SHE), the design of strong SHE materials has become a focus in the field of spintronics. Because of the recent experimental progress also the spin Nernst effect ... More
Optical signature of Weyl electronic structures in tantalum pnictides Ta$Pn$ ($Pn=$ P, As)May 24 2017Jun 30 2017To investigate the electronic structure of Weyl semimetals Ta$Pn$ ($Pn=$P, As), optical conductivity [$\sigma(\omega)$] spectra are measured over a wide range of photon energies and temperatures, and these measured values are compared with band calculations. ... More
Heteroepitaxial growth of tetragonal Mn$_{2.7-x}$Fe$_{x}$Ga$_{1.3}$ (0 $\leqslant$ x $\leqslant$ 1.2) Heusler films with perpendicular magnetic anisotropyMay 30 2017This work reports on the structural and magnetic properties of Mn$_{2.7-x}$Fe$_{x}$Ga$_{1.3}$ Heusler films with different Fe content x (0 $\leqslant$ x $\leqslant$ 1.2). The films were deposited heteroepitaxially on MgO single crystal substrates, by ... More
Proximity Enhanced Quantum Spin Hall State in GrapheneSep 25 2013Feb 26 2015Graphene is the first model system of two-dimensional topological insulator (TI), also known as quantum spin Hall (QSH) insulator. The QSH effect in graphene, however, has eluded direct experimental detection because of its extremely small energy gap ... More
Strong, anisotropic anomalous Hall effect and spin Hall effect in chiral antiferromagnetic compounds Mn$_3X$ ($X$ = Ge, Sn, Ga, Ir, Rh and Pt)Oct 13 2016We have carried out a comprehensive study of the intrinsic anomalous Hall effect and spin Hall effect of several chiral antiferromagnetic compounds, Mn$_3X$ ($X$ = Ge, Sn, Ga, Ir, Rh and Pt) by $ab~initio$ band structure and Berry phase calculations. ... More
Anomalous transport properties of the halfmetallic ferromagnets Co2TiSi, Co2TiGe, and Co2TiSnJul 21 2009In this work the theoretical and experimental investigations of Co2TiZ (Z = Si, Ge, or Sn) compounds are reported. Half-metallic ferromagnetism is predicted for all three compounds with only two bands crossing the Fermi energy in the majority channel. ... More
Electronic structure, magnetism, and disorder in the Heusler compound Co$_2$TiSnSep 22 2006Nov 14 2006Polycrystalline samples of the half-metallic ferromagnet Heusler compound Co$_2$TiSn have been prepared and studied using bulk techniques (X-ray diffraction and magnetization) as well as local probes ($^{119}$Sn M\"ossbauer spectroscopy and $^{59}$Co ... More
Two different topological insulator phases in NaBaBiMar 03 2015By breaking the inversion symmetry of the three-dimensional Dirac metal Na$_3$Bi, we realize topological insulator (TI) phases in the known compound NaBaBi using $ab~initio$ calculations. Two distinct TI phases emerge: one phase is due to band inversion ... More
Strong, anisotropic anomalous Hall effect and spin Hall effect in chiral antiferromagnetic compounds Mn$_3X$ ($X$ = Ge, Sn, Ga, Ir, Rh and Pt)Oct 13 2016Apr 04 2017We have carried out a comprehensive study of the intrinsic anomalous Hall effect and spin Hall effect of several chiral antiferromagnetic compounds, Mn$_3X$ ($X$ = Ge, Sn, Ga, Ir, Rh and Pt) by $ab~initio$ band structure and Berry phase calculations. ... More
Prediction of the Weyl semimetal in the orthorhombic MoTe2Aug 14 2015Sep 29 2015We investigate the orthorhombic phase (Td) of layered transition-metal-dichalcogenide MoTe$_2$ as a Weyl semimetal candidate, which was discovered to be a superconductor in our recent experiment. MoTe$_2$ exhibits four pairs of Weyl points lying slightly ... More
Minimizing hysteresis in martensite phase transforming magnetocaloric Heusler alloysJun 13 2018The large magnetocaloric effect in Heusler alloys showing martensite phase transformation puts them forward as efficient materials for magnetic refrigeration. However, irreversibility of the magnetocaloric cooling cycle is a major challenge for real applications. ... More
Magnetic Weyl Semimetal in Quasi Two-dimensional Half Metallic Co$_3$Sn$_2$Se$_2$Dec 24 2017Mar 28 2018We have found a ferromagnetic Weyl semimetal (WSM) in half metallic Co$_3$Sn$_2$Se$_2$. The three pairs of Weyl points near Fermi level (E$_F$) are derived from nodal lines gapped by spin-orbit coupling (SOC). Though the Weyl points are 0.11 eV above ... More
The role of ionized impurity scattering on the thermoelectric performances of rock salt AgPbmSnSe2+mApr 13 2016We report on the successful synthesis and on the properties of polycrystalline AgPbmSnSe2+m (m = ++++, 100, 50, 25) samples with a rock salt structure. Between 160 K and 400 K, the dominant scattering process of the carriers in this system changes from ... More
Theoretical search for half-Heusler topological insulatorsMay 06 2014We have performed ab-initio band structure calculations on more than two thousand half-Heusler compounds in order to search for new candidates for topological insulators. Herein, LiAuS and NaAuS are found to be the strongest topological insulators with ... More
Half-metallic ferromagnetism with high magnetic moment and high Curie temperature in Co$_2$FeSiNov 18 2005Co$_2$FeSi crystallizes in the ordered L2$_1$ structure as proved by X-ray diffraction and M\"o\ss bauer spectroscopy. The magnetic moment of Co$_2$FeSi was measured to be about $6\mu_B$ at 5K. Magnetic circular dichroism spectra excited by soft X-rays ... More
Magnetically Switchable Light-Matter Interaction in the Two-Dimensional Magnet CrI3Mar 14 2019Coupling different physical properties is a fascinating subject of physics. Already well-known are the multiferroics which show properties of ferroelectrics and magnets. But ferroelectricity by itself also entails the bulk photovoltaic effect, a light-matter ... More
A critical study of the elastic properties and stability of Heusler compounds: Phase change and tetragonal $X_{2}YZ$ compoundsApr 06 2017In the present work, the elastic constants and derived properties of tetragonal and cubic Heusler compounds were calculated using the high accuracy of the full-potential linearized augmented plane wave (FPLAPW). To find the criteria required for an accurate ... More
Indium-Gallium Segregation in CuIn$_{x}$Ga$_{1-x}$Se$_2$: An ab initio based Monte Carlo StudyApr 07 2010Thin-film solar cells with CuIn$_x$Ga$_{1-x}$Se$_2$ (CIGS) absorber are still far below their efficiency limit, although lab cells reach already 19.9%. One important aspect is the homogeneity of the alloy. Large-scale simulations combining Monte Carlo ... More
Rectangular Tantalum Carbide Halides TaCX (X = Cl, Br, I) monolayer: Novel Large-Gap Quantum Spin Hall InsulatorFeb 28 2016Quantum spin Hall (QSH) insulators possess edge states that are topologically protected from backscattering. However, known QSH materials (e.g. HgTe/CdTe and InAs/GaSb quantum wells) exhibit very small energy gap and only work at low temperature, hindering ... More
Embedding ergodic actions of compact quantum groups on C*-algebras into quotient spacesApr 13 2006Sep 21 2013The notion of compact quantum subgroup is revisited and an alternative definition is given. Induced representations are considered and a Frobenius reciprocity theorem is obtained. A relationship between ergodic actions of compact quantum groups on C*-algebras ... More
Theory of quantum radiation observed as sonoluminescenceJun 15 1995Sonoluminescence is explained in terms of quantum radiation by moving interfaces between media of different polarizability. In a stationary dielectric the zero-point fluctuations of the electromagnetic field excite virtual two-photon states which become ... More
Unitary Dual of p-adic U(5)Dec 09 2014We study the parabolically induced complex representations of the unitary group in 5 variables, $ U(5), $ defined over a p-adic field. Let $F$ be a p-adic field. Let $E : F$ be a field extension of degree two. Let $Gal(E : F ) = \{ 1, \sigma \}.$ We write ... More
Almost Vanishing Polynomials for Sets of Limited Precision PointsJul 22 2008Aug 24 2008Let X be a set of s points whose coordinates are known with only limited From the numerical point of view, given a set X of s real points whose coordinates are known with only limited precision, each set X* of real points whose elements differ from those ... More
$L^p$ and Sobolev boundedness of pseudodifferential operators with non-regular symbol: a regularisation approachNov 04 2010In this paper we investigate $L^p$ and Sobolev boundedness of a certain class of pseudodifferential operators with non-regular symbols. We employ regularisation methods, namely convolution with a net of mollifiers $(\rho_\eps)_\eps$, and we study the ... More
A Large-Scale Regularity Theory for Random Elliptic Operators on the Half-Space with Homogeneous Neumann Boundary DataMar 13 2017In this note we derive large-scale regularity properties of solutions to second-order linear elliptic equations with random coefficients on the half- space with homogeneous Neumann boundary data; it is a companion to arXiv:1604.02717 in which the situation ... More
Closed graph and open mapping theorems for topological $\wt{\C}$-modules and applicationsAug 03 2006Oct 17 2006We present closed graph and open mapping theorems for $\wt{\C}$-linear maps acting between suitable classes of topological and locally convex topological $\wt{\C}$-modules. This is done by adaptation of De Wilde's theory of webbed spaces and Adasch's ... More