Results for "Claudia Felser"

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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
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
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
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
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
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
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
Lattice Instability and Competing Spin Structures in the Double Perovskite Insulator Sr2FeOsO6Jul 09 2013Aug 29 2013The semiconductor Sr2FeOsO6, depending on temperature, adopts two types of spin structures that differ in the spin sequence of ferrimagnetic iron - osmium layers along the tetragonal c-axis. Neutron powder diffraction experiments, 57Fe M\"ossbauer spectra, ... More
Magnetoresistance and anomalous Hall effect in micro-ribbons of the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$Dec 24 2018Magnetic Weyl semimetals exhibit intriguing transport phenomena due to their non-trivial band structure. Recent experiments in bulk crystals of the shandite-type Co$_3$Sn$_2$S$_2$ have shown that this material system is a magnetic Weyl semimetal. To access ... More
Quantized Photocurrents in the Chiral Multifold Fermion System RhSiFeb 08 2019The rapid pace of discovery of new classes of Weyl semimetals is driving a search for properties that derive from their unique bandstructure topology. One of the most striking of the predicted properties is the quantized circular photogalvanic effect ... 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
Impurity screening and stability of Fermi arcs against Coulomband magnetic scattering in a Weyl monopnictideJun 01 2016Jan 12 2017We present a quasiparticle interference study of clean and Mn surface-doped TaAs, a prototypical Weyl semimetal, to test the screening properties as well as the stability of Fermi arcs against Coulomb and magnetic scattering. Contrary to topological insulators, ... More
Antiferromagnetic structure and electronic properties of BaCr2As2 and BaCrFeAs2Jan 11 2017The chromium arsenides BaCr2As2 and BaCrFeAs2 with ThCr2Si2 type structure (space group I4/mmm; also adopted by '122' iron arsenide superconductors) have been suggested as mother compounds for possible new superconductors. DFT-based calculations of the ... More
All Electrical Access to Topological Transport Features in Mn$_{1.8}$PtSn FilmsDec 19 2018The presence of non-trivial magnetic topology can give rise to non-vanishing scalar spin chirality and consequently a topological Hall or Nernst effect. In turn, topological transport signals can serve as indicators for topological spin structures. This ... 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
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
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
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
Giant anomalous Hall angle in a half-metallic magnetic Weyl semimetalDec 19 2017Dec 31 2017Magnetic Weyl semimetals (WSMs) with time reversal symmetry breaking exhibit Weyl nodes that act as monopoles of Berry curvature and are thus expected to generate a large intrinsic anomalous Hall effect (AHE). However, in most magnetic WSMs, the Weyl ... 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
Multiple Dirac cones at the surface of the topological metal LaBiMay 23 2016Aug 12 2016The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties including an extremely large and anisotropic magnetoresistance. Experimental evidence for topological surface states is still missing although band inversions have been postulated ... 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
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
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
Berry curvature unravelled by the Nernst effectFeb 05 2019The discovery of topological quantum materials represents a striking innovation in modern condensed matter physics with remarkable fundamental and technological implications. Their classification has been recently extended to topological Weyl semimetals, ... 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Lattice-site-specific spin-dynamics in double perovskite Sr2CoOsO6Dec 03 2013Mar 24 2014We have studied the magnetic properties and spin-dynamics of the structurally-ordered double perovskite Sr$_2$CoOsO$_6$. Our neutron diffraction, muon spin relaxation and ac-susceptibility measurements reveal two antiferromagnetic (AFM) phases on cooling ... 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
Extremely high magnetoresistance and conductivity in the type-II Weyl semimetals WP2 and MoP2Mar 13 2017Nov 23 2017The peculiar band structure of semimetals exhibiting Dirac and Weyl crossings can lead to spectacular electronic properties such as large mobilities accompanied by extremely high magnetoresistance. In particular, two closely neighbouring Weyl points of ... More
Extremely high conductivity observed in the unconventional triple point fermion material MoPMar 10 2017Weyl and Dirac fermions have created much attention in condensed matter physics and material science. They are realized in semimetals that have 2-fold and 4-fold degenerate crossing points and exhibit novel and exotic properties. Recently, several distinct ... 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
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
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
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
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
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
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
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
Chemical disorder as engineering tool for spin-polarizationin Mn3Ga-based Heusler systemsDec 10 2014Dec 12 2014Our study highlights spin-polarization mechanisms in metals, by focusing on the mobilities of conducting electrons with different spins instead of their quantities. Here, we engineer electron mobility by applying chemical disorder induced by non-stoichiometric ... More
Systematical, experimental investigations on LiMgZ (Z= P, As, Sb) wide band gap semiconductorsAug 02 2011This work reports on the experimental investigation of the wide band gap compounds LiMgZ (Z = P, As, Sb), which are promising candidates for opto-electronics and anode materials for Lithium batteries. The compounds crystallize in the cubic (C1_b) MgAgAs ... More
Weak topological insulators induced by the inter-layer coupling: A first-principles study of stacked Bi2TeIJul 30 2013Based on first-principles calculations, we predict Bi2TeI, a stoichiometric compound synthesized, to be a weak topological insulator (TI) in layered subvalent bismuth telluroiodides. Within a bulk energy gap of 80 meV, two Dirac-cone-like topological ... More
Heusler 4.0: Tunable MaterialsDec 18 2016Feb 01 2017Heusler compounds are a large family of binary, ternary and quaternary compounds that exhibit a wide range of properties of both fundamental and potential technological interest. The extensive tunability of the Heusler compounds through chemical substitutions ... 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
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
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
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
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
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
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
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
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
Variation of the bonding interactions and magnetism in GdAuX (X = Mg, Cd, and In)Sep 27 2007Results of first-principles electronic structure calculations for the isotypic compounds GdAuX (ZrNiAl type, X = Mg, Cd, and In) are presented. We report on a systematic examination of the electronic structure and nature of the bonding in these intermetallics. ... More
Investigation of Co$_2$FeSi: The Heusler compound with Highest Curie Temperature and Magnetic MomentNov 18 2005This work reports on structural and magnetic investigations of the Heusler compound Co$_2$FeSi. X-Ray diffraction and M\"o\ss bauer spectrometry indicate an ordered $L2_1$ structure. Magnetic measurements by means of X-ray magnetic circular dichroism ... More
Temperature-induced inversion of the spin-photogalvanic effect in WTe$_2$ and MoTe$_2$Feb 08 2018We investigate the generation and temperature-induced evolution of optically-driven spin photocurrents in WTe$_2$ and MoTe$_2$. By correlating the scattering-plane dependence of the spin photocurrents with the symmetry analysis, we find that a sizeable ... More
Magnetic and transport properties of tetragonal- or cubic-Heusler-type Co-substituted Mn-Ga epitaxial thin filmsNov 12 2012The composition dependence of the structural, magnetic, and transport properties of epitaxially grown Mn-Co-Ga films were investigated. The crystal structure was observed to change from tetragonal to cubic as the Co content was increased. In terms of ... More
Magnetic dichroism in angular resolved hard X-ray photoelectron spectroscopy from buried magnetic layersOct 16 2012This work reports on the measurement of magnetic dichroism in angular-resolved photoelectron spectroscopy from in-plane magnetized buried thin films. The high bulk sensitivity of hard X-ray photoelectron spectroscopy (HAXPES) in combination with circularly ... More
Topological insulators in filled skutteruditesApr 01 2011We propose new topological insulators in cerium filled skutterudite (FS) compounds based on ab initio calculations. We find that two compounds CeOs4As12 and CeOs4Sb12 are zero gap materials with band inversion between Os-d and Ce-f orbitals, which are ... More
Electronic structure of fully epitaxial Co2TiSn thin filmsOct 27 2010In this article we report on the properties of thin films of the full Heusler compound Co2TiSn prepared by DC magnetron co-sputtering. Fully epitaxial, stoichiometric films were obtained by deposition on MgO (001) substrates at substrate temperatures ... More
Loss of anisotropy in strained ultrathin epitaxial L10 Mn-Ga filmsJun 14 2013In this work we are investigating the effect of strain in ultrathin Mn-Ga thin films on the magnetic properties at room temperature. Two different Mn-Ga compositions of which one is furthermore doped with Co were grown on Cr buffered MgO (001) substrates. ... More
The efficient spin injector scheme based on Heusler materialsMar 30 2011We present the rational design scheme intended to provide the stable high spin-polarization at the interfaces of the magneto-resistive junctions by fulfilling the criteria of structural and chemical compatibilities at the interface. This can be realized ... More
Magnetic dichroism study on Mn$_{1.8}$Co$_{1.2}$Ga thin film using a combination of X-ray absorption and photoemission spectroscopyJan 16 2015Using circularly polarised radiation and a combination of bulk-sensitive hard X-ray photoelectron spectroscopy and X-ray-absorption spectroscopy (XAS) we studied the electronic and magnetic structure of epitaxial Mn$_{1.8}$Co$_{1.2}$Ga thin films. Spin ... More
Mesoscopic superconductivity and high spin polarization coexisting at metallic point contacts on the Weyl semimetal TaAsJul 18 2016A Weyl semimetal is a topologically non-trivial phase of matter that hosts mass-less Weyl fermions, the particles that remained elusive for more than 80 years since their theoretical discovery. The Weyl semimetals exhibit unique transport and magneto-transport ... More
Temperature-dependent charge transport in the compensated ferrimagnet Mn$_{1.5}$V$_{0.5}$FeAl from first principlesOct 12 2017We present an ab-initio study of the temperature-dependent longitudinal and anomalous Hall resistivities in the compensated collinear ferrimagnet Mn$_{1.5}$V$_{0.5}$FeAl. Its transport properties are calculated using the general fully relativistic Kubo--Bastin ... More
Superconductivity in Weyl Semimetal Candidate MoTe2Aug 14 2015Mar 02 2016In recent years, layered transition-metal dichalcogenides (TMDs) have attracted considerable attention because of their rich physics; for example, these materials exhibit superconductivity, charge density waves, and the valley Hall effect. As a result, ... 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
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
Sonoluminescence as quantum vacuum radiationJun 15 1995Sonoluminescence is explained in terms of quantum radiation by moving interfaces between media of different polarizability. It can be considered as a dynamic Casimir effect, in the sense that it is a consequence of the imbalance of the zero-point fluctuations ... More