Superconductivity at 23 k in pt doped bafe2as2 single crystals. Andersen the discovery of superconductivity in fdoped lafeaso 1. Meets maximum leakage of 100 microampsft at 75 kv for 3 minutes. In contrast to the cuprates, the febased system appears to tolerate considerable disorder in. Hightemperature superconductivity in iron pnictides occurs when electrons and. Thermal conductivity tensor of single crystalline codoped. Outline iron pnictides hightc superconductivity from itinerant or localized electrons. For ba 1x k x fe 2 as 2 the specific heat capacity jump at t c measured over the whole extent of.
Thermal conductivity was calculated based on equation 3. In the study on their superconducting mechanism, the spins, orbitals, lattices, and their couplings, have been pointed out to have possible roles in realizing the hight c superconductivity, because they are multi. Superconductivity induced by ni doping in bafe2as2 single. We report the discovery of superconductivity at high pressure in srfe2as2 and. Medium pressure hydraulic applications where shock hazards exist and non conductivity is required.
Superconductivity occurs before the structural distortion of the parent compound bafe 2 as 2 x0 is completely suppressed by doping see phase diagram. It has a worldwide membership of around 50 000 comprising physicists from all sectors, as well as those with an interest in physics. Extraordinary magnetic behaviors, resistivity properties, and lattice parameters of the main sample bafe2as2 and bafe2. Bafe 2 as 2 has a rich and flexible materials chemistry that makes it an ideal model. Generally speaking, conductivity is the rate at which matter or energy can pass through a given material. By performing synchrotron xray powder diffraction measurements with diamond anvil cells up to 26. Band structure and electrical conductivity in semiconductors. Superconducting gap symmetry in bafe 2as 2 based superconductors 1. Superconductivity induced by doping platinum in bafe2as2. Decoupling of the superconducting and magneticstructural. Of course, this measurement has diverse practical applications, from using. The bulk superconductivity in codoped bafe 2 as 2 below t c 22 k is demonstrated by resistivity, magnetic susceptibility, and specific heat data.
Sundar materials science division, indira gandhi centre for atomic research kalpakkam 603102, tamilnadu, india abstract the evolution of pressure induced superconductivity in single crystal as well as. While bafe2as2 remains metallic at all temperatures, we observe a depletion in the far infrared energy interval of the optical conductivity below tsdw, ascribed to the formation of a. They offer transition temperatures as high as 55 k as well as essentially isotropic, and extremely large, upper, superconducting critical fields, in excess of 40 t at 20 k. Although much attention has been focused on understanding the interplay between magnetism. Bafe2as2 is structurally simple, available as highquality large crystals, can be both hole and electron doped, and is amenable to firstprinciples electronic structure calculations. A new generation of superconductors is needed with high transition temperatures but that are relatively isotropic. Materials and mechanisms of superconductivity 2012, jul 2012, washington dc, united states. The notation p 0 indicates the low pressure limiting value is given. Bafe2as2 is the parent compound of a family of unconventional superconductors with critical. Thermal conductivity tensor has been measured using single crystalline codoped bafe 2 as 2 down to 0. A reassessment of the strain model of superconductivity and a. Pressure dependence of the bafe2as2 fermi surface within. A model platform for unconventional superconductivity.
Calculated conductivity of al2o3 is similar to those measured for metallic fluid h, n, o, rb, and cs. We present a systematic investigation of the antiferromagnetic ordering and structural distortion for the series of bafe1. Neutron and xray diffraction measurements demonstrate that, unlike for the electrondoped compounds, the structural and magnetic transitions remain coincident in temperature. Possible unconventional superconductivity in substituted bafe 2 as. Variations in atomic geometry affect electron hopping between fe atoms5,6 and the fermi surface topology, influencing magnetic frustration and the pairing mechanism through changes of orbital overlap and occupancies711.
The discovery of hight c superconductivity in ironbased compounds, however, drastically alters this concept, as the origin of its superconductivity is closely related to magnetism of iron. We report the discovery of superconductivity in ybdoped bafe 2 as 2. Two samples were available, one grown on caf 2 substrate and the other on mgo with an fe buffer layer. Pdf a brief overview of changes in the superconducting transition temperature under pressure and evolution of specific heat capacity jump at tc for. The superconducting transition temperatures are up to 27 k in. What controls the phase diagram and superconductivity in. Superconductivity in undoped bafe2as2 by tetrahedral. This is the first example of superconductivity induced by electron doping in this family of materials. Structural evolution with pressure is used to understand this behavior. Superconductivity at 23 k in pt doped bafe2as2 single crystals s r saha 1,tdrye, k kirshenbaum1,npbutch, p y zavalij2 and johnpierre paglione1 1 center for nanophysics and advanced materials, department of physics, university of maryland, college park, md 20742, usa 2 department of chemistry and biochemistry, university of maryland, college. A comparative study on thermal conductivity of al2o3water. Doping dependence of spin excitations and its correlations. A highpressure method was used to systematically dope an antiferromagnetically metallic compound, bafe2as2, with pt, and the doped compounds were studied using xray diffraction, energy.
Bafe2as2 122 is a parent of fesc that transitions from the tetragonal i4mmm nonmagnetic state into the orthorhombic fmmm sdw striped. A brief overview of changes in the superconducting transition temperature under pressure and evolution of specific heat capacity jump at t c for two related families of ironbased superconductors, ba 1x k x fe 2 as 2 0. Materials database thermal properties thermtest inc. A material with a high level of electrical conductivity, for instance, would easily accommodate the movement of an electric charge. A reassessment of the strain model of superconductivity. The goal was to investigate films magnetic and superconducting properties, their reciprocal interplay, and the role played by the fe buffer layer in modifying them. Hightemperature superconductivity in doped bafe2as2.
In contrast to the cuprates, the bafe2as2 system appears to. Magnetic properties of bafe2as2 from spinspiral calculations a. Like in cuprates, hightemperature superconductivity is implemented by. The density of states, magnetic properties, nearfermi band compositions, together with the sommerfeld coefficients. Neutron scattering studies of some nafeas and bafe2as2. The electrical conductivity of al2o3 under shockcompression. However, the correlation between thermal conductivity and bulk. This chart gives the thermal conductivity of gases as a function of temperature. In the past few years, the pnictides have been found as a new class of unconventional superconductors 3,7,8,9,10,11,12. Pdf superconductivity induced by doping platinum in bafe2as2. Jan 11, 2016 the electrical conductivity of our bi 2 te 3 single crystal nr was also increased to 0.
Normalstate and superconducting properties of codoped. Article open caxis pressureinduced antiferromagnetic order in optimally pdoped bafe 2as 0. The bulk materials have been prepared by the solidstate reaction method and sealed into a quartz tube. Pressure induced superconductivity in bafe2as2feplcm. Superconductivity at 38k in the iron arsenide ba1xkxfe2as2. More interestingly, there are no measured, significant changes in the shape of the.
Superconductivity up to 29 k in srfe2as2 and bafe2as2 at. Thermal properties of copper thermal conductivity of copper. The discovery of superconductivity in the lafeaso ref. Loading effect of aluminum hydroxide onto the mechanical. Bafe 2 as 2 is the parent compound of a family of unconventional superconductors with critical temperatures approaching 40 k. Both of these systems manifest substantial t c values when the structuralantiferromagnetic phase transitions are suf. Sglass is no longer made by agy, but used to have a reactive epoxy size. As shown in figure 1c, under an applied pressure of 5. The recently discovered feasbased superconductors are a new, promising set of materials for technological and basic research. The discovery of high t c superconductivity in ironbased compounds, however, drastically alters this concept, as the origin of its superconductivity is closely related to magnetism of iron.
Noncrystalline systems eg glass have much lower conductivity. The discovery of superconductivity with a transition temperature, tc, up to 65 k in singlelayer fese bulk tc8 k films grown on srtio3 substrates has attracted special attention to febased. For 11type, the frequency dependence of the complex conductivity can be understood as that of bcstype superconductor near the superconducting gap energy, and we estimated the superconducting gap energy to be 0. This result indicates that small uniaxial stress along caxis strongly suppresses the structuralantiferromagnetic ordering and stabilizes superconductivity at much lower pressure. Thermal properties of aluminum liquid thermal conductivity of aluminum. At ambient pressure it undergoes a phase transition from a metallic tetragonal phase to an orthorhombic antifer. The terahertz and infrared spectra of the complex dynamic conductivity, as well as the temperature dependences of the density of a superconducting condensate and the electronic specific heat of superconducting bafe 1. We find that substitution of ru for fe is isoelectronic, i. A small increase of t c is observed, as expected for nearly opd samples 3. Electronic structure of the bafe2as2 family of ironpnictide. The crystal structure of all samples exhibited the thcr2si2type crystal structure. Evidence for signchanging gaps between hole pockets in heavily holedoped ba,kfe 2as 2.
Observation of the node lifting by disorder in bafe 2as,p 2 2. Bafe2as2 is the parent compound of a family of unconventional superconductors with critical temperatures approaching 40 k. Pressure dependence of the bafe2as2 fermi surface within the. Nanofluids, thermal conductivity enhancement, al 2 o 3 cuo hybrid nanofluids 1. The ternary iron arsenide bafe2as2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. Layered materials are known to exhibit highly anpansions over some temperature ranges. Unless otherwise noted, the values refer to a pressure of 100 kpa 1 bar or to the saturation vapor pressure if that is less than 100 kpa. Thermal and electrical conduction of singlecrystal bi 2 te 3. Neutrondiffraction measurements of magnetic order and a structural transition in the parent bafe2as2 compound of feasbased hightemperature superconductors q. Generic sglass fiber, s2 glass and sglass have the same composition. Role of magnetism in superconductivity of bafe2as2 physical. Thermal conductivity of gases chart engineers edge. Since the discovery of hightemperature superconductivity hts in ironbased compounds, a variety of systems with different spacer layers have been fabricated. Yanina fasano, et al electron irradiation of co, ni, and pdoped bafe2as2 type ironbased superconductors.
At this additional transition ordered magnetic moments reorient from in. Pressureinduced superconductivity in bafe2as2 single crystal. Neutrondiffraction measurements of magnetic order and a. Strain induced superconductivity in the parent compound. In the 1111 phase family, superconductivity is mostly induced by electron doping, i. Similar to the cuprates, superconductivity in these systems appear in proximity to magnetically ordered phases and strong magnetic fluctuations persist in paramagnetic superconductors. The tiny difference of hydrostaticity between the cubic anvil apparatus and modified bridgman anvil cell induces a drastic effect on the phase diagram of bafe2as2. A cartoon of magnetic flux vortices penetrating through a sample is shown in fig. Sci china mater crystal structure and phase diagrams of ironbased superconductors xigang luo xianhui chen mater. Based on firstprinciple flapwgga calculations, we have investigated the electronic structure of the newly discovered oxygenfree 38k superconductor ba 1. The reason that e 2 is only visible in the cut perpendicular to the x direction is likely due to a combination of its orbital.
Neutron scattering is an ideal probe to study spinspin correlations and hence the interplay between magnetism and superconductivity. Despite different materials, pressures and temperatures, and compression techniques, both experimental and theoretical, conductivities of all these poor metals reach a common end state typical of strongscattering disordered materials. Electronic structure of the bafe2as2 family of iron. Bafe2as2 has a rich and flexible materials chemistry that makes it an ideal model. Hall data indicate that the dominant carriers are electrons, as expected from simple chemical reasoning.
Superconductivity at 22 k in codoped bafe2as2 crystals. The discovery of the hight c iron pnictide superconductor lafeaso 1x f x 1 stimulated the search for related superconductors, and various febased systems have been found. Superconductivity can be induced with the application of pressure but it disappears eventually upon heavy compression in the ironbased parent compound bafe2as2. Kamihara y, watanabe t, hirano m, hosono h 2008 ironbased layered superconductor lao1xfx feas x 0. Feastype tetrahedral ly coordinated layers are the key structural ingredient in all iron based superconducting materials known to date. The recent discovery of superconductivity with relatively high transition temperature tc in the layered ironbased quaternary oxypnictides lao1. Here we report the interplay of magnetic and structural transitions in a parent compound of ironbased. The institute of physics iop is a leading scientific society promoting physics and bringing physicists together for the benefit of all.
We observe peak anomalies both in the thermal conductivity and the thermal hall conductivity in the superconducting state as an indication of enhancement of the quasiparticle meanfree path. Possible unconventional superconductivity in substituted. A systematic characterization of codoped bafe 2 as 2 ba122 thin films has been carried out. The experimental thermal conductivity values were compared with the theoretical thermal conductivity values. Here, we experimentally demonstrate a systematic approach. However, progress has slowed in achieving highperformance 11 tapes by the pit method 23.
A special feature of the arsenide superconductors is that application of external pressure and iso. Magnetic properties of bafe2as2 from spinspiral calculations. In addition, they may well provide insight into exotic superconductivity that extends beyond. Superconductivity in the socalled 111 phase compound lifeas with a similar structure has also been reported. Spin excitation anisotropy in the paramagnetic tetragonal. Superconductivity at 22 k in codoped bafe 2 as 2 crystals athena s. Super conductivity can be induced by partially replacing ba by k in bafe 2as 2 to form holedoped ba 1. Superconductivity in ybdoped bafe2as2 sciencedirect. Superconductor science and technology paper related content.
Structural feature controlling superconductivity in. Febased superconductors exhibit a diverse interplay between charge, orbital, and magnetic ordering14. Thermal conductivity, k 3 where t is the sample thickness m, q is the sample conductivity value w, a is the tested surface area of. The possible existence of a signchanging gap symmetry in bafe2as2derived superconductors sc has been an exciting topic of research in. Highresolution measurements of the thermal expansion of. These results suggest the importance of distortion of feas4 tetrahedra, in stabilizing the. Magnetic ordering and structural distortion in rudoped. Bafe 2 as 2 is structurally simple, available as highquality large crystals, can be both hole and electron doped, and is amenable to firstprinciples electronic structure calculations. Therefore, technologists are still hoping for materials, which have high superconducting transition temperatures and show preferably isotropic behavior. B, condensed matter 8110 january 2010 with 40 reads.
Cleaved surface of bafe2as2 is as terminated ba layer destroyed, some random ba atoms observed on surface no surface reconstruction some evidence of orbital order since only one dos of one type of as was detected bulk asfe and asba interlayer distances are 1. We use high resolution angleresolved photoemission to study the electronic structure of the iron based hightemperature superconductors bafe1xrux2as2 as a function of ru concentration. Various silanes and starch oil are used as binders. Under pressure, the transition temperatures in bafe2as2, are found to be a strong function of hydrostaticity of the pressure cell.
The pt doped system showed a domelike superconductivity region in the thermal phase diagram 0. Pressure induced superconductivity in bafe 2as 2 single crystal awadhesh mani, nilotpal ghosh, s. The superconducting transition temperature for the crystals was determined by dc magnetic susceptibility measurements with a commercial squid magnetometer. Recently, we have reported a transport j c as high as 1. Two textile brands temperature40of to 212of 40oc to 100oc nonconductive nonconductive. Electron irradiation of co, ni, and pdoped bafe2as2 type. Improving superconductivity in bafe 2 as 2 based crystals by cobalt clustering and electronic uniformity. The magnetic field in flux vortices destroys superconductivity inside them, but the regions between flux vortices retain the superconducting state. Pressuredecoupled magnetic and structural transitions of. Superconductivity induced by doping platinum in bafe2as2 by xiyu zhu, fei han, gang mu, jun tang, jing ju, katsumi tanigaki and haihu wen get pdf 863 kb. These studies point out that the thermal conductivity of bricks is mainly related to their bulk density, so that increasing the thermal insulating properties implies the production of materials with a higher porosity jungk et al. Structural and superconductivity properties of bafe 2.
33 1274 793 1539 1091 306 1312 704 974 1135 1260 1006 1040 273 19 618 1341 64 1248 1351 712 1015 1120 383 797 808 1296 376 1251 370 537 1417 1398 1293 1002 1254 803 1023 946 432 1363 847 1048 1417 348 1110