The results show that the temperature dependence of h, 3 is t, ti2 unlike in homogeneous super conductors where it is linear. The physical properties of these unconventional superconductors and the application of the twoband ginzburglandau theory to these superconducting compounds are. In the case of ironbased superconductors, the neutron resonance has been extensively studied experimentally, and a peculiar spinspace anisotropy has been identi. Many metals have high strength and high elastic module. Manipulation of magnetic anisotropy in ferromagnetic. Effect of induced shape anisotropy on magnetic properties of ferromagnetic cobalt nanocubes d. Photoemission spectroscopic evidence of gap anisotropy in. Phenomenological description of anisotropy effects in some. Inplane transport anisotropy in a ba1xkxfe2as2 iron.
Strong anisotropy effect in an ironbased superconductor cafe0. Photoemission spectroscopic evidence of gap anisotropy in an. In a biaxial superconductor with m a, m b,andm c all. Pdf the calcium intercalated graphite cac 6 is considered to be a representative material of the graphite intercalated superconductors, which. Weidner measurements of relaxation times in a copper tutton salt at liquidhelium. Bealmonod, maki, and coworkers14 have shown that the orthorhombic distortion leads necessarily to an admixture of swave component in ad1s superconductivity model. Anisotropy and strongcoupling effects on the collective mode.
Pairing symmetry from inplane torque anisotropy in tlba cuo. Weiss pseudodipolar anisotrophy in cubic ferromagnets at low temperatures 1959 schick, kenneth l. Critical current anisotropy in high temperature superconductors. Following the discovery of superconductivity in magne sium diboride mgb2. Mehta 2 1 school of physical sciences, jawaharlal nehru university, new delhi 110067, india 2 thin film laboratory, department of physics, indian institute of technology delhi, new delhi 110016, india 3 ugcdae consortium for scientific research. After nearly 15 years of research effort, high temperature superconductors hts. This is most likely due to fast degradation of sample surfaces andor different.
Physical properties of high temperature superconductors i. The effects of planar anisotropy on these properties are closely related to the changes in the quasiparticledensity of states due to anisotropy. All superconducting materials known at ordinary pressures currently work far below ambient. The conditions for its application k fl d super conductors vortices quantum hall. Evidence for a temperature dependent anisotropy of the. The relative importance of the pauli and orbital limiting can be described by the socalled maki parameter a.
The anisotropy of ironbased superconductors is much smaller than that of the cuprates and that predicted by theoretical calculations. Takanaka department of engineering science, tohoku university, sendai, japan received 25 may 1979 by w. Anisotropic superconductivity and dimensional crossover in. Currentvoltage characteristics in ybco and bscco, at temperatures near the superconducting transition, exhibit nonohmic responses with power dependence v al. The layered structure of many unconventional super conductors is not only linked with the usual high critical temperaturesofthesematerials. Anisotropy of vortexliquid and vortexsolid phases in. Tunneling studies have provided scattered gap values of 0. Okolna 2, 50422 wroclaw, poland 2institute of solid state physics ifp, karlsruhe institute of technology, d76021, karlsruhe, germany email.
In a bandstructure model by combescot and leyronas15 the coupling between chains and planes in ybco. Anisotropy of superconductivity from mgb2 single crystals nims. The anisotropy of the superconducting order parameter and the mechanism of pairing interactions in layered super conductors are recent subjects of much interest. Anisotropic lower critical field of superconductors. Generally, for the resistive transition in the presence of a magnetic field, the effect. Anisotropy of thermal conductivity and possible signature. If the defect structure is isotropic, the current anisotropy is governed solely by the. The effect of defects and impurities in hightemperature superconductors. Emergent magnetic anisotropy in the cubic heavyfermion. Vortex liquid crystals in anisotropic type ii superconductors e. Apart of experimental results on real materials where anisotropy is important like organic conductors 4 or multifilamentary super conducting wires 5 there exist few publications concerned with the influence of anisotropy on percolative conduction. They can be strengthened by alloying and heat treatment.
Vortex liquid crystals in anisotropic type ii superconductors. Effects of the anisotropy on the nonohmic behaviour in high. Interaction of vortices in anisotropic superconductors. It is found that the concentration dependent transition temperature shows typical departures from the corresponding curve of a singleband isotropic superconductor. Pdf revealing the anisotropy effects on the critical magnetic field. Effects of magnetic anisotropy on the subgap excitations. Concerning the magnetic properties, remarkable agreement between theory and experiment has been achieved. The effects of planar anisotropy on these properties are closely related to the. In particular, hightc cuprate superconductors, organic superconductors, and the sr2ruo4 compound have been studied by many authors. Anisotropic superconductivity mediated by phonons in. Anisotropy and strongcoupling effects on the collective. Anisotropy and multiband effects this book presents the anisotropy and multiband effects in newly discovered unconventional super conductors. Critical temperature of an anisotropic superconductor containing. Tunneling 5, microwave penetration depth 6, and raman 7 measurements all yield evidence for some kind of nearly uniformly gapped fermi surface.
Unfortunately, the hightemperature superconductor class has had many definitions in the context of superconductivity. The spectral peaks and their splitting due to the magnetic anisotropy in the multichannel case are discussed in sec. Angular dependence of vortex instability in a layered. Anisotropy effects in superconductors with magnetic. Manufacturing properties of engineering materials lecture notes. Anisotropy effects in superconductors springerlink. Workshop on the magnetic properties of lowdimensional systems. Furthermore, 18 papers present the most recent research on these properties and additional anisotropy effects associated with the intermediate state patterns or the specific heat. Anisotropy effects on flux pinning and flux flow are strongly effective in cuprate as well as ironbased superconductors due to their intrinsically layered crystallographic structure. Campbell1,2 1department of physics, boston university, boston, massachusetts 02215 2department of electrical and computer engineering, boston university, boston, massachusetts 02215 received 5 september 2002. Strong electron correlation effects in complex d and f. Mehta 2 1 school of physical sciences, jawaharlal nehru university, new delhi 110067, india.
Pdf on jan 1, 2012, iman askerzade and others published unconventional superconductors anisotropy and multiband effects find, read and cite all the research you need on researchgate. Strong electron correlation effects in complex d and fbased. Electrical magnetochiral anisotropy in a bulk chiral. The preparation stages of the fesi no strips include a cold rolled to intermediate. Sasaki the orientation dependence of the lower critical field j1 in the super conductors with cubic symmetry is qualitatively discussed near the transition temperature. S8 45 indeed shows that the zerobias ldos is locked to the crystal rather than. Pairing symmetry from inplane torque anisotropy in tlba. They maintain their good strength at high and low temperatures. Because of these anisotropy effects, and because the round conductors may offer advantages for use with ac current, several companies are exploring the use of round, multifilamentary bscco2212superconductors for applications below 40 k. The influence of fermi surface anisotropy on the superconducting transition temperature of strong coupling superconductors containing magnetic and nonmagnetic impurities is investigated. Anisotropic superconducting properties including the upper critical field hc2. The label hight c should be reserved for materials with critical temperatures greater than the boiling point of liquid nitrogen.
I have shown that it is possible to engineer the easy axis of magnetization to inplane or outofplane with adequate phosphorous doping. Section vi is devoted to the role of the external magnetic. Strong electron correlation effects in complex dand fbased magnetic materials for technological applications june 30 july 2, 2014 prague, czech republic sponsored by the k network of european science fondation and organized by the institute of physics academy of sciences cr union of czech mathematicians and physicists association of. Electrical magnetochiral anisotropy phenomenon describes the change in resistance of chiral materials caused by the interplay between chirality, conductivity and magnetic fields. Because of its dissimilarity to bronzeprocess conductors, an internaltin nb,sn conductor was selected for this study to directly address the effect of grain morphology on the transverse stress effect. However, it may be worthwhile to discuss the anisotropy of. The physical properties of these unconventional superconductors and the application of the two.
Anisotropy of vortexliquid and vortexsolid phases in single. Anisotropic properties and critical behavior of hightemperature. Symmetrybreaking orbital anisotropy observed for detwinned. Unconventional superconductors anisotropy and multiband effects. C super conductors also exhibit a nematic phase in the form of a tetragonaltoorthorhombic structural transition that either precedes or accompanies the onset of longrange antiferromagnetic order 7, 8, both of which are suppressed with doping leading to super conductivity 911.
We account for this anisotropy by allowing different effective masses in the three crystalline directions, which we will call m a, m b,andm c. Such bedding plane anisotropy can also be achieved by both macroscopic and microscopic layering of minerals clays or rock units sandshale sequences. The changes in the quasiparticlelifetimedue to the superconductingphase transition and anisotropy are also important for the unusual behaviors of thermal conduc tivity at low temperature. Hea to chiral superconductors with strong anisotropy. An experimental model for studying the effect of anisotropy. However, our understanding of this subject is far from being complete. The discovery of ferromagnetic superconductors uge2 1, uruge 2, ucoge 3, in which ferromagnetic ordering coexists with superconductivity. The anisotropic static and dynamical properties of super conductors have commonly been described by the threedimensional ginzburglandau3dgl. Effects of the anisotropy on the nonohmic behaviour in. However, it may be worthwhile to discuss the anisotropy of the critical.
The same behaviour was observed in isovalentlysubstituted bafe 1. Tc, strong evidence is found in this work for such finite size effects and a. This book presents the anisotropy and multiband effects in newly discovered unconventional superconductors. Upper critical field in anisotropic superconductors. Inplane transport anisotropy in a ba1xkxfe2as2 ironbased. Anisotropy of thermal conductivity and possible signature of the fuldeferrelllarkinovchinnikov state in cecoin5 c. In the quantum regime k f1 relevant for y123, the vortex size is comparable with the fermi wavelength and the fermisurface anisotropy determines the vortex structure 52,53. Effect of induced shape anisotropy on magnetic properties. The effect on the fll structure crossover of increasing anisotropy has been. Pairing symmetry from inplane torque anisotropy in tl2ba2cuo61dthin. Provided herein is a method of forming a conductive film, the method comprising. Anisotropic superconductivity mediated by phonons in layered. Effect of transverse stress on the critical current of.