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Topological Weyl semimetals (TWSs) with pairs of Weyl points and topologically protected Fermi arc states have broadened the classification of topological phases and provide superior platform for study of topological superconductivity. Here we report the nontrivial superconductivity and topological features of sulfurdoped Td-phase MoTe2 with enhanced Tc compared with type-II TWS MoTe2. It is found that Td-phase S-doped MoTe2 (MoTe2-xSx, x~0.2) is a two-band s-wave bulk superconductor (~0.13 meV and 0.26 meV), where the superconducting behavior can be explained by the s+- pairing model. Further, measurements of the quasi-particle interference (QPI) patterns and a comparison with band-structure calculations reveal the existence of Fermi arcs in MoTe2-xSx . More interestingly, a relatively large superconducting gap (~1.7 meV) is detected by scanning tunneling spectroscopy on the sample surface, showing a hint of topological nontrivial superconductivity based on the pairing of Fermi arc surface states. Our work demonstrates that the Td-phase MoTe2-xSx is not only a promising topological superconductor candidate but also a unique material for study of s+- superconductivity. [ABSTRACT FROM AUTHOR]

Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω-1⋅cm-1 and an anomalous Hall angle as large as 23%. Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition (TN) at 9 K without any noticeable magnetic correlations above TN. Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract The introduction of topological invariants, ranging from insulators to metals, has provided new insights into the traditional classification of electronic states in condensed matter physics. A sudden change in the topological invariant at the boundary of a topological nontrivial system leads to the formation of exotic surface states that are dramatically different from its bulk. In recent years, significant advancements in the exploration of the physical properties of these topological systems and regarding device research related to spintronics and quantum computation have been made. Here, we review the progress of the characterization and manipulation of topological phases from the electron transport perspective and also the intriguing chiral/Majorana states that stem from them. We then discuss the future directions of research into these topological states and their potential applications. [ABSTRACT FROM AUTHOR]

We theoretically study current-induced orbital magnetization in a chiral crystal. This phenomenon is an orbital version of the Edelstein effect. We propose an analogy between the current-induced orbital magnetization and an Ampère field in a solenoid in classical electrodynamics. To quantify this effect, we define a dimensionless parameter from the response coefficients relating a current density with an orbital magnetization. This dimensionless parameter can be regarded as a number of turns within a unit cell when the crystal is regarded as a solenoid, and it represents how "chiral" the crystal is. By focusing on the dimensionless parameter, one can design a band structure that realizes the induction of large orbital magnetization. In particular, a Weyl semimetal with all of the Weyl nodes close to the Fermi energy can have a large value for this dimensionless parameter, which can exceed that of a classical solenoid. [ABSTRACT FROM AUTHOR]

Insulating states can be topologically nontrivial, a well-established notion that is exemplified by the quantum Hall effect and topological insulators. By contrast, topological metals have not been experimentally evidenced until recently. In systems with strong correlations, they have yet to be identified. Heavy-fermion semimetals are a prototype of strongly correlated systems and, given their strong spin-orbit coupling, present a natural setting to make progress. Here, we advance a Weyl-Kondo semimetal phase in a periodic Anderson model on a noncentrosymmetric lattice. The quasiparticles near the Weyl nodes develop out of the Kondo effect, as do the surface states that feature Fermi arcs. We determine the key signatures of this phase, which are realized in the heavy-fermion semimetal Ce3Bi4Pd3. Our findings provide the much-needed theoretical foundation for the experimental search of topological metals with strong correlations and open up an avenue for systematic studies of such quantum phases that naturally entangle multiple degrees of freedom. [ABSTRACT FROM AUTHOR]

The Casimir effect is a quantum phenomenon induced by the zero-point energy of relativistic fields confined in a finite-size system. This effect for photon fields has been studied for a long time, while the realization of counterparts for fermion fields in Dirac/Weyl semimetals is an open question. We theoretically demonstrate the typical properties of the Casimir effect for relativistic electron fields in Dirac/Weyl semimetals and show the results from an effective Hamiltonian for realistic materials such as Cd 3 As 2 and Na 3 Bi. We find an oscillation of the Casimir energy as a function of the thickness of the thin film, which stems from the existence of Dirac/Weyl nodes in momentum space. Experimentally, such an effect can be observed in thin films of semimetals, where the thickness dependence of thermodynamic quantities is affected by the Casimir energy. [ABSTRACT FROM AUTHOR]

• The multi-band nonreciprocal radiation involving Fibonacci multilayer is studied. • Strong quad-band nonreciprocal radiations are achieved due to the FP resonance. • The channel number can be enlarged by simply increasing the Fibonacci order. • The scheme can be used to develop novel energy devices and thermal emitters. The strong multi-band nonreciprocal radiation with Fibonacci multilayer is studied. It consists of a Weyl semimetal planar and a dielectric layer on a Fibonacci multilayer and a metal reflector. Here, without loss of generality, a quad-band nonreciprocal radiation effect is investigated as an illustration. The results show that four pairs of near-perfect absorption and emission are achieved that do not overlapped with each other, leading to perfect quad-channel nonreciprocal radiation. The underlying physical origin is revealed by investing the magnetic field magnitude distributions and is further verified by impedance matching theory. In addition, the influence of incident angle and geometric parameters on spectral nonreciprocity is investigated, and it is found that the performance can remain excellent in a wide range of geometric parameters, which reduces manufacturing costs. What's more, the scheme can be easily expanded to achieve multi-band nonreciprocal radiation with the channel number larger than four by simply increasing the Fibonacci order. We believe that the designed structure should pave the way for the development of nonreciprocal thermal emitters with more advanced functions. [ABSTRACT FROM AUTHOR]

Strained trigonal Te has been predicted to host Weyl nodes supported by a non-symmorphic chiral symmetry. Using low-pressure physical vapor deposition, we systematically explored the growth of trigonal Te nanowires with naturally occurring strain caused by curvature of the wires. Raman spectra and high mobility electronic transport attest to the highly crystalline nature of the wires. Comparison of Raman spectra for both straight and curved nanowires indicates a breathing mode that is significantly broader and shifted in frequency for the curved wires. Strain induced by curvature during growth therefore may provide a simple pathway to investigate topological phases in trigonal Te.

We studied the transport properties of the Weyl-node-mismatch junction, beside which the Weyl nodes are mismatch so that their projections on the interface plane cannot overlap. When electrons of one valley are injected onto the junction, the refraction is not coplanar with the injection-reflection plane. The non-coplanar deviation angle is valley dependent, and so if the injection consists of both valley components, the birefraction will take place. When electrons coming from a narrow rod transit across the junction into the bulk region on the other side, the electrons will be diffracted in the unconfined region. The diffraction is dispersed near the rod-bulk interface and is laterally deflected to the direction along the line connecting the Weyl node projections of incident and transmitted sides.

Motivated by the chiral anomaly steering negative longitudinal magnetoresistance in GdBiPt under external magnetic field, we studied the electronic structures of GdBi with paramagnetism, antiferromagnetism and ferromagnetism by first-principles calculations with modified Becke and Johnson local density approximation plus Hubbard . Our calculated results reveal that paramagnetic GdBi is semiconducting, while the antiferromagnetic GdBi is a topological nontrivial compensation metal. We also predict the presence of a pair of Weyl fermions in ferromagnetic GdBi and GdSb. The band crossing along the direction of magnetization is protected by the fourfold rotation symmetry, and the topological charge associating with each band crossing point is . [ABSTRACT FROM AUTHOR]

Generalized Dirac monopoles in momentum space are constructed in even dimensions from the Weyl Hamiltonian in terms of Green's functions. In dimensions, the (unit) charge of the monopole is equal to both the winding number and the Chern number, expressed as the integral of the Berry curvature. Based on the equivalence of the Chern and winding numbers, a chirally coupled and Lorentz invariant field theory action is studied for the Weyl semimetal phase. At the one loop order, the effective action yields both the chiral magnetic effect and the anomalous Hall effect. The Chern number appears as a coefficient in the conductivity, thus emphasizes the role of topology. The anomalous contribution of chiral fermions to transport phenomena is reflected as the gauge anomaly with the Pfaffian invariant . Relevance of monopoles and Chern numbers for the semiclassical chiral kinetic theory is also discussed. [ABSTRACT FROM AUTHOR]

As novel topological phases in correlated electron systems, we have found two examples of non-ferromagnetic states that exhibit a large anomalous Hall effect. One is the chiral spin liquid compound, which exhibits a spontaneous Hall effect in a spin liquid state due to spin ice correlation. The other is the chiral antiferromagnetsandthat exhibit a large anomalous Hall effect at room temperature. The latter shows a sign change of the anomalous Hall effect by a small change in the magnetic field by a few 100 G, which should be useful for various applications. We will discuss that the magnetic Weyl metal states are the origin for such a large anomalous Hall effect observed in both the spin liquid and antiferromagnet that possess almost no magnetisation. [ABSTRACT FROM PUBLISHER]

Three-dimensional Dirac semimetal is an ideal platform in studying topological phase transitions due to its exotic electronic structure. Based on the effective Hamiltonian of material Na 3 Bi where two degenerated Dirac points are constructed by four Weyl nodes and protected by crystal symmetry, we study its Floquet phase transitions induced by circularly polarized light in off-resonant limit. By breaking the time-reversal symmetry and taking the quadratic momentum into account, abundant phases are realized, including Weyl semimetal, spin-polarized Weyl semimetal (SP-WSM), and normal insulator. The SP-WSM phase is a new phase, in which only pairs of spin-up (or spin-down) opposite-chirality Weyl nodes are remained while the other pairs of spin-down (or spin-up) opposite-chirality Weyl nodes are eliminated. Importantly, all the phase transitions can be manipulated not only by tuning the light intensity but also by changing the incident direction of light. To understand them, we have in detail analyzed the trajectory of Weyl nodes in k space controlled by the circularly polarized light and manifested them with the angle- and spin- dependent Hall conductivity. [ABSTRACT FROM AUTHOR]

By first-principles calculations, we find that PbO 2 is a strongly topological node-line semimetal (NLSM), which is protected by the coexistence of the time-reversal and spatial inversion symmetry when the spin-orbit coupling (SOC) is ignored. In the three dimensions Brillouin zone, there are two node-line rings around the Γ point, perpendicular to each other. It is different to the previously NLSM which has one or three node-line rings in the Brillouin zone. The drumhead-like surface states also can be obtained on both the (100) and (010) surfaces. When the SOC is included, a small gap opened along the nodal line, this material becomes a topological insulator. Therefore, our discovery renders an ideal platform for experimental exploration of the fundamental physics of topological node-line semimetals. [ABSTRACT FROM AUTHOR]

We present a comparative investigation on structural, elastic, dynamical and thermodynamic properties of Weyl semimetals MX ( M = Ta or Nb; X = As or P) using density functional theory (DFT) within the generalized gradient approximation. The elastic properties of NbAs, TaP and NbP are obtained for the first time, then we compared them with each other and with some well-studied materials. Among four Weyl semimetals, TaP and NbAs possess the largest and smallest bulk modulus B , shear modulus G , and Young's modulus E , respectively, while NbP and TaAs own the maximum and minimum elastic Debye temperature. Through the analysis of three dimensional (3D) representations and two dimensional (2D) projections of Young's modulus, MX series exhibit distinct elastic anisotropy, especially for TaAs and NbAs. The calculated phonon dispersions of four Weyl semimetals show no imaginary frequency throughout the Brillouin zone, indicating they are dynamically stable. In addition, compared with other theoretical results, our calculated Brillouin-zone-center frequencies of MX series are more in line with experimental data. Furthermore, Phonon velocities are obtained using phonon spectra, and anisotropic phonon group velocities are responsible for their anisotropic lattice thermal conductivity. Additionally, thermodynamic properties are also predicted using the calculated phonon density of states. The results are in good agreement with available experimental values. We expect our work can provide more information for further experimental studies. [ABSTRACT FROM AUTHOR]

Topological materials have attracted considerable experimental and theoretical attention. They exhibit strong spin-orbit coupling both in the band structure (intrinsic) and in the impurity potentials (extrinsic), although the latter is often neglected. In this work, we discuss weak localization and antilocalization of massless Dirac fermions in topological insulators and massive Dirac fermions inWeyl semimetal thin films, taking into account both intrinsic and extrinsic spin-orbit interactions. The physics is governed by the complex interplay of the chiral spin texture, quasiparticle mass, and scalar and spin-orbit scattering. We demonstrate that terms linear in the extrinsic spin-orbit scattering are generally present in the Bloch and momentum relaxation times in all topological materials, and the correction to the diffusion constant is linear in the strength of the extrinsic spin-orbit. In topological insulators, which have zero quasiparticle mass, the terms linear in the impurity spin-orbit coupling lead to an observable density dependence in the weak antilocalization correction. They produce substantial qualitative modifications to the magnetoconductivity, differing greatly from the conventional Hikami-Larkin-Nagaoka formula traditionally used in experimental fits, which predicts a crossover from weak localization to antilocalization as a function of the extrinsic spin-orbit strength. In contrast, our analysis reveals that topological insulators always exhibit weak antilocalization. In Weyl semimetal thin films having intermediate to large values of the quasiparticle mass, we show that extrinsic spin-orbit scattering strongly affects the boundary of the weak localization to antilocalization transition. We produce a complete phase diagram for this transition as a function of the mass and spin-orbit scattering strength. Throughout the paper, we discuss implications for experimental work, and, at the end, we provide a brief comparison with transition metal dichalcogenides. [ABSTRACT FROM AUTHOR]

A Weyl semimetal (WSM) features Weyl fermions in its bulk and topological surface states on surfaces, and is novel material hosting Weyl fermions, a kind of fundamental particles. The WSM was regarded as a three-dimensional version of 'graphene' under the illusion. In order to explore its promising photoelectric properties and applications in photonics and photoelectronics, here, we study the anisotropic linear and nonlinear optical responses of a WSM TaAs, which are determined by the relationship and balance between its topological surface states and Weyl nodes. We demonstrate that topological surface states which break the bulk symmetry are responsible for the anisotropy of the mobility, and the anisotropic nonlinear response shows saturable characteristic with extremely large saturable intensity. We also find that the mobility is anisotropic with the magnitude of 104 cm2V−1s−1 at room temperature and can be accelerated by the optical field. By analyzing the symmetry, the nonlinear response is mainly contributed by the fermions close to the Weyl nodes, and is related to the Pauli's blocking of fermions, electron-electron interaction. This work experimentally discovers the anisotropic ultrahigh mobility of WSMs in the optical field and may start the field for the applications of WSMs in photonics and photoelectronics. [ABSTRACT FROM AUTHOR]

Abstract Weyl fermion is a massless Dirac fermion with definite chirality, which has been long pursued since 1929. Though it has not been observed as a fundamental particle in nature, Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the surface. As a firstly discovered Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum space, which are topologically protected against small perturbations. Here, we report for the first time the tip induced superconductivity on TaAs crystal by point contact spectroscopy. The zero bias conductance peak as well as a conductance plateau with double conductance peaks and sharp double dips are observed in the point contact spectra simultaneously, indicating unconventional superconductivity. Our further theoretical study suggests that the induced superconductivity may have nontrivial topology. The present work opens a new route in investigating the novel superconducting states based on Weyl materials. [ABSTRACT FROM AUTHOR]

The transition metal dipnictides TaAs2, TaSb2, NbAs2 and NbSb2 have recently sparked interest for exhibiting giant magnetoresistance. While the exact nature of the magnetoresistance in these materials is still under active investigation, there are experimental results indicating that it is of the anisotropic negative variety. We study the effect of magnetic fields on the band structure topology of these materials by applying Zeeman splitting. In the absence of a magnetic field, we find that the materials are weak topological insulators, which is in agreement with previous studies. When the magnetic field is applied, we find that type-II Weyl points form. This result is found first from a symmetry argument, and then numerically for a k · pmodel of TaAs2 and a tight-bindingmodel of NbSb2. This effect could be of help in the search for an explanation of the anomalous magnetoresistance in these materials. [ABSTRACT FROM AUTHOR]

• The nonreciprocal thermal radiation can be attained. • The incident angle bringing about the nonreciprocal thermal radiation can be as small as 15°. • The WDMSes is operated over the mid-infrared wave range around 4.692 and 3.89 µm. • Stronger performance of the nonreciprocal thermal radiation is realized with η >0.95. • The effects of t on nonreciprocal thermal properties are studied. This work proposes the Weyl semimetal-dielectric multilayer structures (WDMSes), both sides of which can realize nonreciprocal thermal radiation. Utilizing the transfer matrix method, the absorptivity α q and emissivity e q are calculated in the mid-infrared wave range. The absorption can be attributed to the defect modes. For both sides of the WDMSes, it is found the nonreciprocity originates as the incident angle is around 15° and a wider incident angle tends to enhance it. By increasing the angle to 45°, the stronger nonreciprocal thermal radiation for the front side is revealed at the wavelength of 4.692 µm and 3.890 µm. In the same way, for the back side, it is displayed at the wavelength of 4.692 µm and 3.896 µm. The relevant factors including the temperature of the Weyl semimetal, the thickness of the dielectric layer unit, the thickness of the defect layer, and the period of the structure are discussed. They can affect the nonreciprocity, as well as shift the absorption and emission bands in the wave and angular range. This work can be applied to heat radiation transfer media, energy conversion devices, thermal storage and emitter, and so on. [ABSTRACT FROM AUTHOR]

We investigate the magnetotransport in Weyl semimetal with broken time reversal symmetry. Weyl semimetals, with and without disorder, having different shapes of Fermi arcs are examined. The different shape of Fermi arc surface states are due to two different considerations of model Hamiltonian one with broken inversion symmetry and other with preserved inversion symmetry. We numerically investigate the magnetotransport in z -direction when magnetic field is in the x -direction perpendicular to the Weyl semimetal slab. For the first case with broken inversion symmetry we get two counterpropagating states on each edge i.e. one edge has only n -type states and other has only p -type states. When an electron (hole) reservoir is connected to the slab in z -direction, only n -type (p -type) edge channel passes through the contact for an applied bias. For the second case in which inversion symmetry is preserved we get only p -type states on each edge, propagating in the opposite direction at each edge, very similar to 2D quantum Hall effect. The transverse magnetoconductance σ z y is an integer multiple of e 2 / h for both the cases. We numerically investigate the effect of disordered impurity potential on the propagating states along z -direction. The edges states are not very robust in the presence of disorder for the first case but for the second case, edge states can persist upto a certain value of disorder strength. We further investigate the magnetotransport in y -direction with finite boundaries in z -direction for both the cases under the effect of tilted magnetic field. Tilting the magnetic field modifies the number of chiral Landau levels lying on the Fermi level and hence the value of transverse magnetoconductance σ y z. The magnetoconductance along z and y directions are due to different shapes of orbits along the z – y edges. The transverse magnetoconductance in y -direction is found to be robust against the disordered impurity potential which may be the signature of quantum Hall effect in 3D. Our research may be helpful in finding Weyl materials with such type of magnetotransport properties. • Weyl semimetals having different shapes of Fermi arcs are investigated numerically. • The effect of disorder on edge states in a perpendicular magnetic field is studied. • The magnetoconductance along the edges are due to different shapes of Wely orbits. • The tilted magnetic field modifies the chiral Landau levels lying on the Fermi level. • The transverse magnetoconductance found to be quantized is robust against disorder. [ABSTRACT FROM AUTHOR]

• Fast response, compared to other shaped microstructures, the wire grid restricts the carrier migration direction, reducing the two-dimensional carrier diffusion direction to one-dimensional, the device will also have a faster response. • The polarisation-resolved, wire-gate structure causes the device to respond differently to terahertz waves of different polarisations, so the device can be used for specific modulation of terahertz waves of different polarisations. • The preparation scheme is simple and low cost, suitable for use in 6G communication devices, and can be prepared in large quantities with precision. • The combination of SPPs, polarisation resolution and ultra-fast response, together with accurate preparation and high volume production, makes it very convenient for applications such as 6G communication encoders. The 6th generation (6G) of communication technology, defines 0.1–1 THz as the communication band. As a result, ultrafast modulation and multi-dimensional resolution coding technologies in the terahertz band pose a big challenge. In this work, a polarization-resolved ultrafast optical controlled terahertz modulator has been realized by combining tungsten ditelluride (WTe 2) thin film with subwavelength metallic gratings. In the frequency range of 0.1–1.2 THz, which covers the 6G frequency band, the modulation depth of the device reaches up to 36.8% with a centimeter-scale effective area. An ultrafast response time of 0.95 ps is obtained due to the limitations of the grating for carrier degrees of freedom. In addition, the polarization sensitivity of terahertz waves polarized in the x- and y-direction is up to 0.77 due to the sub-wavelength grating structure. The results give a chance to develop the large-area, high-performance polarization-resolved ultrafast THz modulators based on Weyl semimetal, which could provide a reliable alternative for 6G communications equipment. [ABSTRACT FROM AUTHOR]

• A 4 × 4 magneto-optical matrix is established to investigate the transmittances of the forward and backward left hand circularly polarized (LCP) waves impinging the 4 μm thickness Weyl semimetal (WSM) at normal incidence. • The propagation characteristics of two LCP waves exhibit differently due to the distinct effective permittivity caused by the off-diagonal term. • With the increase of wavelength, the two waves experience blocking transmission, bidirectional transmission and unidirectional transmission, respectively. • The wavelength of the unidirectional transmission is quite wide, which can be utilized to design the broadband optical isolator. • The threshold wavelength of the optical isolator shows tunability of the Fermi energy, tilt degree of Weyl cones and Weyl node separation. We theoretically set up a 4 × 4 magneto-optical matrix to investigate the transmittances induced by the forward and backward left hand circularly polarized (LCP) waves impinging the 4 μm thickness Weyl semimetal (WSM) material at normal incidence. Because of the different effective permittivity of the two LCP waves in WSM induced by the non-zero off-diagonal term, the two waves experience blocking transmission, bidirectional transmission and unidirectional transmission with the increase of the wavelength, respectively. Based on the wide wavelength of the unidirectional transmission, the broadband optical isolator can be realized. The threshold wavelength of the optical isolator can be regulated by changing the wavelength where the parallel component of the diagonal element is identical to the off-diagonal term. It is also found that the Fermi energy, tilt degree of Weyl cones and Weyl node separation reveal simple and available approaches to achieve the regulation. We believe that the adjustable broadband compact optical isolator can perform a significant role in fiber-optic communication system. [ABSTRACT FROM AUTHOR]

Fluctuations in planar magnetotransport are ubiquitous in topological HgTe structures, in both tensile (topological insulator) and compressively strained layers (Weyl semimetal phase). We show that the common reason for the fluctuations is the presence of tilted Dirac cones combined with the formation of charge puddles. The origin of the tilted Dirac cones is the mix of the Zeeman term due to the in-plane magnetic field and quadratic contributions to the dispersion relation. We develop a network model that mimics the transport of tilted Dirac fermions in the landscape of charge puddles. The model captures the essential features of the experimental data. It should be relevant for the interpretation of planar magnetotransport in a variety of topological and small band gap materials.

Spin-orbit torque (SOT) is receiving tremendous attention from both fundamental and application-oriented aspects. Co 2 MnGa, a Weyl ferromagnet that is in a class of topological quantum materials, possesses cubic-based high structural symmetry, the L2 1 crystal ordering, which should be incapable of hosting anisotropic SOT in conventional understanding. Here we show the discovery of a gigantic anisotropy of self-induced SOT in Co 2 MnGa. The magnitude of the SOT is comparable to that of heavy metal/ferromagnet bilayer systems, despite the high inversion symmetry of the Co 2 MnGa structure. More surprisingly, a sign inversion of the self-induced SOT is observed for different crystal axes. This finding stems from the interplay of the topological nature of the electronic states and their strong modulation by external strain. Our research enriches the understanding of the physics of self-induced SOT and demonstrates a versatile method for tuning SOT efficiencies in a wide range of materials for topological and spintronic devices.

B20-CoSi is a newly discovered Weyl semimetal that crystallizes into a noncentrosymmetric crystal structure. However, the investigation of B20-CoSi has so far been focused on bulk materials, whereas the growth of thin films on technology-relevant substrates is a prerequisite for most practical applications. In this study, we have used millisecond-range flash-lamp annealing, a nonequilibrium solid-state reaction, to grow B20-CoSi thin films. By optimizing the annealing parameters, we were able to obtain thin films with a pure B20-CoSi phase. The magnetic and transport measurements indicate the appearance of the charge density wave and chiral anomaly. Our work presents a promising method for preparing thin films of most binary B20 transition-metal silicides, which are candidates for topological Weyl semimetals.

We propose a simple realization of a three-dimensional Weyl semimetal phase using off-resonant circularly polarized light in the three dimensional Dirac semimetals. Using both analytical and numerical methods, we show that a fourfold degenerate Dirac node can be further evolved into two Weyl nodes in the context of low energy Hamiltonian. The distance between the two Weyl nodes in momentum space can be controlled by the intensity and frequency of the light. Meanwhile, because this distance is proportional to the relatively large Fermi velocity, the typical character of the Weyl semimetal, such as surface Fermi arc, can be observed obviously. [ABSTRACT FROM AUTHOR]

The existence of Weyl nodes predicted in TaAs has been confirmed by angle-resolved photoemission spectroscopy, which provides potential applications in thermoelectric devices due to the extraordinary transport properties of TaAs. By using first-principles calculations and semiclassical Boltzmann transport theory, we study the electrical transport properties of TaAs. High anisotropy is observed in the electrical transport of TaAs. The obtained Seebeck coefficients are in good agreement with experimental values. The lattice dynamics properties of TaAs are also investigated and the obtained phonon frequencies agree well with the measurements. The lattice thermal conductivity is calculated using the self-consistent iterative approach. Anisotropic lattice thermal conductivity is observed as well. Maximum thermoelectric figure of merit zT of 0.63 at 900 K is found for n-doping TaAs along zz direction. Finally, the size dependence of lattice thermal conductivity and corresponding thermoelectric properties are investigated for designing thermoelectric nanostructures. The work sheds light on the nature of the thermoelectric response of Weyl semimetal. [ABSTRACT FROM AUTHOR]