Niobium Phosphide Research Articles

Origin of the extreme and anisotropic magnetoresistance in the Weyl semimetal NbP

The fascination with semimetals, especially Dirac and Weyl semimetals, is given by their surprisingly strong response to magnetic fields. In particular, the extremely large magnetoresistance (XMR), i.e., the change in electrical resistivity as a function of the applied magnetic field, has attracted interest because of its deviation by several orders of magnitude from the behavior of normal metals, and its potential for technological applications. To date, it is unclear if the XMR in topological semimetals is inherently correlated to the very high electron mobility and electron-hole compensation, or to other exotic mechanisms. Here, we show that the relativistic and topological nature of charge carriers of the Weyl semimetal niobium phosphide (NbP) are only indirect causes of the XMR. Instead, the XMR can be explained by the very long mean free path le(4K)≈8µm in combination with the small cyclotron orbits emerging in the presence of a magnetic field rc(9T)≈20 nm of the NbP's Weyl electrons. More precisely we find MR=cle/rc, where c is a parameter independent of temperature and angle between the magnetic field and the crystal. To demonstrate, we use temperature and angle-dependent magnetoresistance measurements, and extract the mean free path and cyclotron radius from an analysis of the Shubnikov–de Haas oscillation. Published by the American Physical Society 2024

Ultrafast Sub-100 fs All-Optical Modulation and Efficient Third-Harmonic Generation in Weyl Semimetal Niobium Phosphide Thin Films.

Since their experimental discovery in 2015, Weyl semimetals have generated a large amount of attention due their intriguing physical properties that arise from their linear electron dispersion relation and topological surface states. In particular, in the field of nonlinear (NL) optics and light harvesting, Weyl semimetals have shown outstanding performances and achieved record NL conversion coefficients. In this context, the first steps toward Weyl semimetal nanophotonics are performed here by thoroughly characterizing the linear and NL optical behavior of epitaxially grown niobium phosphide (NbP) thin films, covering the visible to the near-infrared regime of the electromagnetic spectrum. Despite the measured high linear absorption, third-harmonic generation studies demonstrate high conversion efficiencies up to 10-4 % that can be attributed to the topological electron states at the surface of the material. Furthermore, nondegenerate pump-probe measurements with sub-10 fs pulses reveal a maximum modulation depth of ≈1%, completely decaying within 100 fs and therefore suggesting the possibility of developing all-optical switching devices based on NbP. Altogether, this work reveals the promising NL optical properties of Weyl semimetal thin films, which outperform bulk crystals of the same material, laying the grounds for nanoscale applications, enabled by top-down nanostructuring, such as light-harvesting, on-chip frequency conversion, and all-optical processing.

Topological properties after light ion irradiation on Weyl semimetal niobium phosphide from first principles

A member of the nonmagnetic Weyl semimetal family, niobium phosphide (NbP), is a new low-energy dissipative material due to the properties of its nontrivial energy band structure and topologically protected nodes. This paper mainly focus on the changes of the topological properties of the crystal NbP after H and He ions irradiation, a novel research view. In order to demonstrate the formation process of doping defects, we use TD-DFT to simulate the whole path of H ion passing the bulk NbP, while both the total energy change for system and the radial drag force as a function of the projectile position are investigated. The energy band structures and density of states for the equilibrium point defect have been analyzed by means of the DFT method based on the CASTEP package. A strikingly phenomenon discovered is that diverse kinds of defects are able to modify the symmetrically protected Weyl points to some extent. Specifically, when H or He as an interstitial particle in the crystal NbP, the degenerate bands are uncoupled; meanwhile, the Fermi levels are shifted upward 0.12 eV and 0.18 eV, respectively. In contrast to the defect structures formed by P, the defects caused by Nb present the greater destructive power to the Weyl points. By contrast, the calculations of formation energy have demonstrated that H substitute for Nb is the most easily formed defect structure, and the defect with interstitial H atom is most stable structure within the scope of this research.

Landau Quantization in Coupled Weyl Points: A Case Study of Semimetal NbP.

Weyl semimetal (WSM) is a newly discovered quantum phase of matter that exhibits topologically protected states characterized by two separated Weyl points with linear dispersion in all directions. Here, via combining theoretical analysis and magneto-infrared spectroscopy of an archetypal Weyl semimetal, niobium phosphide, we demonstrate that the coupling between Weyl points can significantly modify the electronic structure of a WSM and provide a new twist to the protected states. These findings suggest that the coupled Weyl points should be considered as the basis for analysis of realistic WSMs.

Berry phase and band structure analysis of the Weyl semimetal NbP.

Weyl semimetals are often considered the 3D-analogon of graphene or topological insulators. The evaluation of quantum oscillations in these systems remains challenging because there are often multiple conduction bands. We observe de Haas-van Alphen oscillations with several frequencies in a single crystal of the Weyl semimetal niobium phosphide. For each fundamental crystal axis, we can fit the raw data to a superposition of sinusoidal functions, which enables us to calculate the characteristic parameters of all individual bulk conduction bands using Fourier transform with an analysis of the temperature and magnetic field-dependent oscillation amplitude decay. Our experimental results indicate that the band structure consists of Dirac bands with low cyclotron mass, a non-trivial Berry phase and parabolic bands with a higher effective mass and trivial Berry phase.

Observation of Fermi Arcs in Non-Centrosymmetric Weyl Semi-Metal Candidate NbP**Supported by the National Natural Science Foundation of China under Grant Nos 11174124, 11274068, 11374137, 11421404 and 13ZR1451700, and the National Basic Research Program of China (973 Program) under Grant No 2012CB921402.

We report the surface electronic structure of niobium phosphide NbP single crystal on (001) surface by vacuum ultraviolet angle-resolved photoemission spectroscopy. Combining with our first principle calculations, we identify the existence of the Fermi arcs originated from topological surface states. Furthermore, the surface states exhibit circular dichroism pattern, which may correlate with its non-trivial spin texture. Our results provide critical evidence for the existence of the Weyl Fermions in NbP, which lays the foundation for further research.

White Phosphorus Activation at a Metal–Phosphorus Triple Bond: a New Route to cyclo-Triphosphorus or cyclo-Pentaphosphorus Complexes of Niobium

The Nb-P triple bond in [P≡Nb(N[Np]Ar)(3)](-) (Np = CH(2)(t)Bu; Ar = 3,5-Me(2)C(6)H(3)) has produced the first case of P(4) activation by a metal-ligand multiple bond. Treatment of P(4) with the sodium salt of the niobium phosphide complex in weakly coordinating solvents led to formation of the cyclo-P(3) anion [(P(3))Nb(N[Np]Ar)(3)](-). Treatment in tetrahydrofuran (THF) led to the formation of a cyclo-P(5) anion [(Ar[Np]N)(η(4)-P(5))Nb(N[Np]Ar)(2)](-), which represents a rare example of a substituted pentaphosphacyclopentadienyl ligand. The P(4) activation pathway was shown to depend on the dimer-monomer equilibrium of the niobium phosphide reagent, which, in turn, depends on the solvent used for the reaction. The pathway leading to the cyclo-P(3) product was shown to require a 2:1 ratio of the phosphide anion to P(4), while the cyclo-P(5) formation requires a 1:1 ratio. The cyclo-P(3) salt has been isolated in 56% yield as orange crystals of the [Na(THF)](2)[(P(3))Nb(N[Np]Ar)(3)](2) dimer or in 83% yield as an orange powder of [Na(12-crown-4)(2)][(P(3))Nb(N[Np]Ar)(3)]. A solid-state X-ray diffraction experiment on the former salt revealed that each Nb-P(3) unit exhibits pseudo-C(3) symmetry, while (31)P NMR spectroscopy showed a sharp signal at -223 ppm that splits into a doublet-triplet pair below -50 °C. It was demonstrated that this salt can serve as a P(3)(3-) source upon treatment with AsCl(3), albeit with modest yield of AsP(3). The cyclo-P(5) salt was isolated in 71% yield and structurally characterized from red crystals of [Na(THF)(6)][(Ar[Np]N)(η(4)-P(5))Nb(N[Np]Ar)(2)]. The anion in this salt can be interpreted as the product of trapping of an intermediate pentaphosphacycplopentadienyl structure through migration of one anilide ligand onto the P(5) ring. The W(CO)(5)-capped cyclo-P(3) salt was also isolated in 60% yield as [Na(THF)][(OC)(5)W(P(3))Nb(N[Np]Ar)(3)] from the activation of 0.5 equiv of P(4) with the sodium salt of the tungsten pentacarbonyl adduct of the niobium phosphide anion.

Carbon–phosphorus triple bond formation through multiple bond metathesis of an anionic niobium phosphide with carbon dioxide

A novel borane-capped niobium phosphide anion ([B(C 6F 5) 3- 1]) has been prepared in 87% yield by reaction of [P Nb(N[Np]Ar) 3] − ( 1, Ar = 3,5-C 6H 3Me 2 and Np = neopentyl) with the Lewis acidic borane B(C 6F 5) 3. Room-temperature reaction of this adduct with carbon dioxide readily yields the OCP − ion 3, isolated as its sodium salt, [Na(dme) 2][OCP] (dme = dimethoxyethane), in 70% yield, with concomitant formation of a borane-substituted niobium oxo complex [B(C 6F 5) 3- 2] ( 2 = ONb(N[Np]Ar) 3).

A trigonal and hindered tertiary phosphine ligand rendered anionic by a niobate anchor: Formation of zwitterionic M(i) (M = Cu, Ag, Au, Rh) complexes

Treatment of terminal phosphide anion [PNb(N[Np]Ar)3]− ([Na(OEt2)]+ salt, Ar = 3,5-Me2C6H3) with two diphenylketene equivalents led to isolation of anion [P(C{CPh2}O)2Nb(N[Np]Ar)3]− in 78% yield as its [Na(THF)]+ salt. The latter reacts with diphenylketene (1 equiv) to provide the triple diphenylketene addition product [P(C{CPh2}O)3Nb(N[Np]Ar)3]− in 88% yield as its [Na(THF)]+ salt; the same material is obtained alternatively in 93% yield by reaction of diphenylketene (3 equiv) directly with niobium phosphide [Na(OEt2)][PNb(N[Np]Ar)3]. The anion [P(C{CPh2}O)3Nb(N[Np]Ar)3]− was also crystallized as its ion-separated [Na(THF)6]+ salt as illuminated by a single-crystal X-ray diffraction study, which also revealed the three-fold symmetric nature of the highly hindered tertiary phosphine comprising the anionic component. Coinage metal monocations of the new, anionic phosphine were prepared via salt elimination; structural studies on the zwitterionic complexes (py)M[P(C{CPh2}O)3Nb(N[Np]Ar)3] (M = Cu, Ag, and Au) showed them to be isostructural in the space groupP21/c while illustrating the ensconcement of a two-coordinate coinage metal in a deep binding pocket flanked by three phenyl residues. Rhodium(I) incorporation into the anion's binding pocket illustrated versatility of the latter: in contrast to structural observations for the M(I) complexes (M = Cu, Ag, and Au), in the case of Rh[P(C{CPh2}O)3Nb(N[Np]Ar)3] an X-ray study reveals strong interactions (η6 and η2, respectively) with two of the three phenyl residues that are proximal to Rh(I) when connected to the phosphine lone pair of the anion.

A Niobaziridine Hydride System for White Phosphorus or Dinitrogen Activation and N‐ or P‐Atom Transfer

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A niobaziridine hydride system for white phosphorus or dinitrogen activation and N- or P-atom transfer

This short review describes a breakthrough embodied by the synthesis of a niobaziridine hydride complex. This reactive entity reacts directly with white phosphorus to provide a bridging diphosphorus diniobium complex that upon reduction splits to afford a terminal niobium phosphide anion, isolated as its sodium salt. Reactions of the latter with acid chlorides constitute a new synthesis of phosphaalkynes, while treatment with chlorodiorganophosphanes leads to complexed 1,1-diorganophosphanylphosphinidene systems. Additionally, reactions of the sodium salt of the niobium phosphide anion with divalent main group element salts (E = Ge, Sn, or Pb) provide complexed triatomic EP2 triangles. Dinitrogen cleavage was realized via reduction of a heterodinuclear niobium/molybdenum dinitrogen complex, and this provided an entry to a nitrogen-15 labeled terminal nitride anion of niobium as its sodium salt. In a fashion analogous to the aforementioned phosphaalkyne synthesis, acid chlorides are transformed upon reaction with the niobium nitride anion into corresponding nitrogen-15 labeled organic nitriles. Complete synthetic cycles are achieved in both the phosphaalkyne and the organic nitrile syntheses, as the oxoniobium(v) byproduct can be recycled in high yield to the title niobaziridine hydride complex.

Triatomic EP2 Triangles (E=Ge, Sn, Pb) as μ2:η3,η3‐Bridging Ligands

Divalent Group 14 salts react with the [Na(thf)x]+ derivative of the terminal niobium phosphide anion [PNb{N(Np)Ar}3]− (Np=neopentyl, Ar=3,5-Me2C6H3) to give complexes of the form [(μ2:η3,η3-cyclo-EP2){Nb[N(Np)Ar]3}2] (E=Ge, Sn, and Pb; see structure). The bridging {cyclo-EP2} units in these complexes can be considered as neutral 2π-electron three-membered rings that are isolobal to the cyclopropenium ion.

Phosphaalkynes from Acid Chlorides via P for O(Cl) Metathesis: A Recyclable Niobium Phosphide (P3-) Reagent that Effects C−P Triple-Bond Formation

Reported herein is a new, metathetical P for O(Cl) exchange mediated by an anionic niobium phosphide complex that furnished phosphaalkynes (RCP) from acid chlorides (RC(O)Cl) under mild conditions. The niobaziridine hydride complex, Nb(H)(tBu(H)C=NAr)(N[Np]Ar)2 (1, Np = neopentyl, Ar = 3,5-Me2C6H3), has been shown previously to react with elemental phosphorus (P4), affording the mu-diphosphide complex, (mu2:eta2,eta2-P2)[Nb(N[Np]Ar)3]2, (2), which can be subsequently reduced by sodium amalgam to the anonic, terminal phosphide complex, [Na][PNb(N[Np]Ar)3] (3). It is now shown that treatment of 3 with either pivaloyl (t-BuC(O)Cl) or 1-adamantoyl (1-AdC(O)Cl) chloride provides the thermally unstable niobacyles, (t-BuC(O)P)Nb(N[Np]Ar)3 (4-t-Bu) and (1-AdC(O)P)Nb(N[Np]Ar)3 (4-1-Ad), which are intermediates along the pathway to ejection of the known phosphaalkynes t-BuCP (5-t-Bu) and 1-AdCP(5-1-Ad). Phosphaalkyne ejection from 4-t-Bu and 4-1-Ad proceeds with formation of the niobium(V) oxo complex ONb(N[Np]Ar)3 (6) as a stable byproduct. Preliminary kinetic measurements for fragmentation of 4-t-Bu to 5-t-Bu and 6 in C6D6 solution are consistent with a first-order process, yielding the thermodynamic parameters DeltaH = 24.9 +/- 1.4 kcal mol-1 and DeltaS = 2.4 +/- 4.3 cal mol-1 K-1 over the temperature range 308-338 K. Separation of volatile 5-t-Bu from 6 after thermolysis has been readily achieved by vacuum transfer in yields of 90%. Pure 6 is recovered after vacuum transfer and can be treated with 1.0 equiv of triflic anhydride (Tf2O, Tf = O2SCF3) to afford the bistriflate complex, Nb(OTf)2(N[Np]Ar)3 (7), in high yield. Complex 7 provides direct access to 1 upon reduction with magnesium anthracene, thus completing a cycle of element activation, small-molecule generation via metathetical P-atom transfer, and deoxygenative recycling of the final niobium(V) oxo product.

ChemInform Abstract: Bonding and Electronic Structure of Superconducting NbPS

Tight-binding band structure calculations performed on the structure of niobium phosphide sulfide are analyzed. The bonding of the linear semicontinuous chain of P atoms present in this material is analyzed with a two-dimensional model; a Nb-P interaction that disrupts the sigma bonding within the chain leads to the observed P-P distances. A crystal orbital centered on the Nb atoms that is nonbonding with the P and S atoms in segments of the Brillouin zone affords a peak in the density of states at the Fermi level that is correlated with the observed high superconducting transition temperature. The metal-to-metal bonding is examined, and the structures and physical properties of some postulated compounds are anticipated.

Bonding and electronic structure of superconducting niobium phosphide sulfide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBonding and electronic structure of superconducting niobium phosphide sulfideDouglas A. Keszler and Roald HoffmannCite this: J. Am. Chem. Soc. 1987, 109, 1, 118–124Publication Date (Print):January 1, 1987Publication History Published online1 May 2002Published inissue 1 January 1987https://doi.org/10.1021/ja00235a020RIGHTS & PERMISSIONSArticle Views401Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (782 KB) Get e-Alerts Get e-Alerts

High-pressure synthesis and structure of the new niobium phosphide Nb2P5

Nb2P 5 was prepared by reaction of the elements at 3-5 GPa and 1273 K using a cubic-anvil-type apparatus. The crystal is orthorhombic, Pnma, with a = 16.742 (3), b = 3.3499 (6), c = 7.912 (1) A, Z = 4, and D x = 5.10 Mg m -a. The structure was refined to R = 0.037 for 1198 independent reflections. The structure of Nb2P 5 is closely related to the OsGe2-type structure. Zigzag P~ chains are additionally inserted along the b axis between the Os2Ge 4 rhombic prisms of the OsGe2-type structure. Nb2P s is a metallic conductor and shows Pauli paramagnetism.

非水溶媒系電解液定電位電解エッチング法による鋼中のリン化物の観察と分析

Phosphides in carbon steel and stainless steel are studied using the non-aqueous electrolytepotentiostatic etching method. The results are summarized as follows.(1) Niobium phosphide is found in austenitic stainless steel (SUS 347). The phosphide is fine and eutectic and located in fracture surface of the steel strained at high temperature by Gleeble Test Device. According to the X-ray diffraction analysis of the residues extracted from the steel, the phosphide is identified as Nb8P5 (orthorhombic: a0=2.62 nm, b0=0.947 nm, c=0.346 nm).(2) Titanium phosphides are found in continuously cast slab of ferritic stainless steel (SUS 430). The phosphides are needle-, plate-like and dendritic. From the X-ray diffraction analysis of the phosphides, Ti3P(Cr3PN type, orthorhombic), Ti4P3(cubic) and TiP(hexagonal) are found.(3) Titanium phosphide is found in carbon steel (0.014%P-0.16%Ti). The phosphide is identified as Ti∼1.7P(orthorhombic) by X-ray diffraction analysis of the extracted residues. Ti/P ratio of the residues is about 1.2. The phosphide precipitates above 873 K and the maximum of the precipitation is found in the temperature range from 973 to 1073 K.

The preparation and properties of some transition phosphides

The monophosphides of some transition metals in Groups IV, V, VI, and VII were prepared by reacting calcium phosphide with metal powders or metal chlorides. The densities, oxidation resistances, thermal stabilities, and hardnesses of the monophosphide powders and compacts were measured to further characterize these compounds. Niobium phosphide, the most stable phosphide of those studied, decomposed at 1,730°C, while MnP, the least stable phosphide, decomposed at 1,100°C. The monophosphides appear metallic, have high electrical conductivities, and are about as hard as hard steel.