Employing green function formalism, the expression for the spin density wave order parameter m and expression for spin density wave transition temperature t sdw is obtained. The ac losses in high tc superconductors can be described by the bean critical state model as long as the exponent n. Hightemperature superconductors are operatively defined as materials that behave as. A new iron based superconductor, ca,prfeas2, was discovered. Physical properties and models of electronic structure are analyzed for a new class of high tc superconductors which belong to iron based layered compounds. Correlation properties and band structure of feas based superconductors vladimir kashurnikov, andrey krasavin. Hightc superconductors based on feas compounds ebook. The coexistence of superconductivity and spin density wave in smo 1x f x feas is theoretically studied using the model hamiltonian which contains bcs type superconductivity and spin density wave terms. Following the laofeastype compounds, which served as a starting point in the study of feasbased hight c superconductors, bafe2as2, srfe2as2 129 and other afe2as2 a k, cs, sr. Platelike crystals of the new phase were obtained, and its crystal structure was investigated by singlecrystal xray diffraction analysis.
Pressureinduced phase transitions and correlation between structure and superconductivity in iron based superconductor ceo0. The icdd pdf coverage of the high tc superconductor and related compounds in the arcuo systems a ba, sr and ca, and r lanthanides and y volume 7 issue 3 winnie wongng. Cuprates, ferropnictides and ferrochalcogenides are three classes of unconventional high temperature superconductors, who share similar. Superconductivity is the set of physical properties observed in certain materials, wherein. Fermi surfaces contain sheets with both electronlike and holelike character in the doped feas based superconductors 20 and in the transuranic superconductor pucoga 5 21. Hightc superconductors based on feas compounds yuri. The 122 iron arsenide unconventional superconductors are part of a new class of iron based superconductors. With the exception of the copper based high tc superconductors, this is the highest tc reported to date. Based on this feaslayered framework, the electronic band. The simplest feasbased superconductor in structure is the afeas. Superconductors ceramic conductors are the socalled high t c superconductors, materials that lose their resistance at much higher critical temperatures than their metal alloy counterparts.
The synthesis and properties of lifeas, a hightc febased superconducting stoichiometric compound, are reported. Unlike the known isoelectronic undoped intrinsic feas compounds, lifeas does not show any spindensity wave behavior but exhibits. Single crystal xray studies reveal that it crystallizes in the tetragonal pbfcl type p4nmm with a3. The structure was identified as the monoclinic system with space group p21m, composed of two capr planes, fe2as2 layers, and as2 zigzag chain layers. Given the itinerant character of charge carriers in ibs, superconductivity sc can be achieved via fermisurface tuning in two possible ways. The second is a rich variety in candidate materials and in pairing interaction. Bulk superconductivity at 21 k is observed after annealing the asprepared sample at 773 k for 40 h. Some of the compounds have been known since 1995, and their semiconductive properties have been known and patented since 2006. Development of conductor based on htsc powderintube technology pit. Realspace pairing through charge transfer excitons in high tc cuprates.
One of the most appropriate model for these compounds is the twoorbital model 9, 10 which is a typical. Physical properties and models of electronic structure are analyzed for a new class of hightc superconductors which belong to ironbased layered compounds. Despite their variable chemical composition and differences in the crystal structure, these compounds possess similar physical. Examples of the use of superconductors in measurement techniques are squid magnetometers and infrared detectors. Reofeas 1111 oxypnictide superconductors several high tc superconductors have been discovered also in other fe based analogues compounds including ternary compound afe2as2 a is an alkali earth metal element such as sr and ba. Any material exhibiting these properties is a superconductor. Physics of ironbased high temperature superconductors. High tc superconductivity in cs3c60 compounds governed by local cs c60. Introduction since the discovery of superconductivity in. Hightemperature superconductivity in ironbased materials arxiv. Fese is the simplest iron based superconductor but with the diverse properties. Pdf hightc superconductivity in iron based pinictides and. Ironbased high transition temperature superconductors national.
This, the first volume on an emerging topic in materials science, examines in depth the physical properties and models of a new class of high tc superconductors which belong to iron based. This definition encompasses a wider variety of unconventional superconductors and is used in the context of theoretical models. Power applications of htsc what are possible applications. Between 1986 and 1994 most advances in the field of superconductivity related to the discovery of new superconductor systems and compounds. Much like high tc copper oxides, superconductivity in the newly discovered the rareearth iron based oxide systems is derived from either electron or hole doping of their nonsuperconducting.
The bcs theory bardeen, cooper, and schrieffer, 1957 17 was based. Exploring domelike tc in new superconductors is of interest to. Since their discovery 1, the classification of hightc superconductors has broadened. Synthesis and characterization of iron arsenic feas. These new materials have tetragonal structure with the p4nmm space group, exactly like the feasbased compounds. Most of the other materials, including lafeaso, are antiferromagnets with t n of the order of 100 k 4. Band structure of feasbased superconductors sciencedirect. Magnetic order close to superconductivity in the iron. The icddpdf coverage of the high tc superconductor and. As well as copper based hightemperature superconductors htsc, these compounds have a layered structure. But different from high tc cuprates that belong to strongly correlated charge transfer type mott compounds, the layered iron arsenide is an itinerant metalsemimetal. Hightc superconductors based on feas compounds core. By synthesis of ba1xkxfe2as2 superconductivity was observed with a critical temperature tc38k.
Unlike an ordinary metallic conductor, whose resistance decreases gradually as its temperature is lowered even down to near absolute zero, a superconductor has a. The shorthand name 122 comes from their stoichiometry. In recent years, except for the discovery of several atypical superconductors, superconductor news has been mainly about novel ways to employ the new generation of ceramic superconductors, innovative. It has turned out that there are many material varieties in iron based superconductors such as 7 parent materials,1111, 122, 111, 112, 245, 11 and. Hightc superconductors based on feas compounds request pdf. Superconductivity under high pressure in the binary compound cali 2 pdf file phys. A highangle annular darkfield image of 110 plane of la2cu5as3o2. Until 2008, only certain compounds of copper and oxygen socalled cuprates were known to have hts properties, and the term hightemperature superconductor was used interchangeably with cuprate superconductor for compounds such as bismuth strontium calcium copper oxide bscco and yttrium barium copper oxide. An increased tc up of 56 k was reported in smo1xfxfeas 7. Pdf the synthesis and properties of lifeas, a hightc febased superconducting stoichiometric compound, are reported. Iron based layered superconductor lao 1x f x feas x 0.
We have synthesized a new oxypnictide, ba2ti2fe2as4o, via a solidstate reaction under a vacuum. Correlation properties and band structure of feasbased. High tc superconductors based on feas compounds yuri izyumov, ernst kurmaev auth. The highest tc in bulk ironbased superconductors is 55 k in. Superconductivity is the set of physical properties observed in certain materials, wherein electrical resistance vanishes and from which magnetic flux fields are expelled. Simplified doping dependent phase diagram of cuprate superconductors for both electron n and hole p doping. Magnetic and superconducting properties of feasbased high tc superconductors with gd article pdf available in jetp letters 905. Physics of iron based high temperature superconductors yuji matsuda department of physics, kyoto university, kyoto 6068502, japan abstract the discovery of high tc iron pnictide and chalcogenide superconductors has been one of the mostexciting recent developments in condensed matter physics. The extremely high magnetic field sensitivity of squids is based on the quantum interference effects described in chapter. High tc superconductors based on feas compounds pp 1254.
The majority of hightemperature superconductors are ceramics materials. Request pdf on jan 1, 2010, yuri izyumov and others published high tc superconductors based on feas compounds find, read and cite all the research you need on researchgate. Compounds of the afe2as2 a ba,sr,ca type springerlink. B, condensed matter 786 august 2008 with 158 reads. Most high t c ceramics are layered structures, with twodimensional copperoxygen sheets along which superconduction takes place. High tc superconductors based on feas compounds pp.
Superconductivity an overview sciencedirect topics. The surprising discovery of superconductivity in layered ironbased materials, with transition temperatures climbing as high as. High t c superconductivity in undoped thfeasn nature. We seek for clues for unconventional superconductivity in the materials. Model the minimal electron model for feas based htsc follows from the crystal structure of these compounds 1 and band structure calculations, that show that the largest contribution to the electronic density of states near the fermi level give 3dstates of iron atoms 14, 23. The label high tc may be reserved by some authors for those with critical temperature greater than the boiling point of liquid nitrogen 77ak or a196aac. Pdf the newly discovered high transition temperature superconductor.
The phases shown are the antiferromagnetic af phase close to zero doping, the superconducting phase around optimal doping, and the. General theory of high t c superconductors 1 wileyvch. Magnetic and superconducting properties of feasbased high. The synthesis and properties of lifeas, a high tc fe based superconducting stoichiometric compound, are reported.
The compound crystallizes in a bodycentered tetragonal lattice, which can be viewed as an intergrowth of bafe2as2 and bati2as2o, thus containing fe2as2 layers and ti2o sheets. The transition temperature tc exhibits a trapezoid shape dependence on the f content, with the highest tc of. Local antiferromagnetic exchange and collaborative fermi surface. Magnetic order in bafe2as2, the parent compound of the feas based superconductors in a new structural family article pdf available july 2008 with 179 reads how we measure reads. Following the laofeastype compounds, which served as a starting point in the study of feas based high t c superconductors, bafe 2 as 2, srfe 2 as 2 129 and other afe 2 as 2 a k, cs, sr compounds have been synthesized, which under doping turned superconducting. In february 2008, an ironbased family of hightemperature superconductors was discovered. Hightc superconductors based on feas compounds pdf free. Potential uses of hightc superconductors are measurement techniques, electronics, magnet and energy applications. The a15 type compounds crystallize in the cubic system, as shown in figure. Despite their variable chemical composition and differences in the crystal structure, these compounds.
Twenty years after the discovery of high temperature superconductors, practical. Evidence for a sharp enhancement of spin fluctuations by nematic order abstract linear magnetor. Hightc superconductors based on feas compounds springer. Ernst kurmaev physical properties and models of electronic structure are analyzed for a new class of high tc superconductors which belong to iron based layered compounds. The copper oxide superconductors are characterized by crystal structures with one or more sheets of cuo 2, separated by insulating block layers. The discovery of a new class of hightemperature superconductors fe based layered compounds aroused a signi. We report that a layered iron based compound laofeas undergoes superconducting transition under doping with f ions at the o2 site. Compound smfeaso showed the evidence of superconductivity at. Pdf magnetic order in bafe2as2, the parent compound of.
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