Show full abstract different families of iron based superconductors, casts new insight into the connections. All five of fes 3 d orbitals make contributions black lines to the fermi level e 0. Structure and superconductivity of the layered iron arsenide. Iron based superconductors fesc are iron containing chemical compounds whose superconducting properties were discovered in 2006. Pdf phase separation and magnetic order in kdoped iron. The newly discovered alkali doped iron selenide superconductors. Superconducting properties of sulfurdoped iron selenide. The first iron based superconductors were identified in 2008 when yi was in graduate school.
Theoretical calculations suggested it to be a mott insulator mi at ambient pressure,20. The newly discovered alkalidoped iron selenide superconductors not only reach a superconducting transition temperature as high as 32 k, but. The iron selenide superconductor has a formula of fe1. Pdf superconductivity in alkali metal intercalated iron. The new superconductors are captivating theorists and experimenters alike. The newly discovered alkalidoped iron selenide superconductors not only reach a superconducting transition temperature as high as 32k, but also exhibit unique characteristics that are absent from other iron based superconductors, such as antiferromagnetically ordered insulating phases, extremely high neel transition temperatures and the presence of fe vacancies and ordering. In 2008, led by recently discovered iron pnictide compounds originally known as oxypnictides, they were in the first stages of experimentation and implementation. This phase exists in a narrow window of stability in the iron selenium binary phase diagram 300 k sep 22, 2016 further lithiation turns off superconductivity again as the stoichiometric parent composition liohfese is obtained following extrusion of elemental iron. The low temperature stable phases are the tetragonal pbostructure p4nmm.
We prepared highquality potassiumdoped iron selenide kxfe2yse2 thin films by molecular beam epitaxy and unambiguously demonstrated the existence of phase. Electric doublelayer transistor using layered iron. Iron based superconductors processing and properties. May 20, 2019 in the pantheon of unconventional superconductors, iron selenide is a rock star. Pdf superconductivity in the iron selenide kxfe2se2 0 superconductivity in the iron selenide kxfe2se2 0 iron based and copperbased superconductors, including high t c values, and proximity of a magnetically ordered state, suggest that the superconductivity in the febased materials is unconventional. However, the newly discovered kdoped iron selenide superconductor k xfe2 yse2 z, lattice structure of kfe2se2 is shown in fig. We report on a new iron selenide superconductor with a tc onset of 45k and the nominal.
Oct 01, 2016 one of the most studied iron based superconductors is iron selenide. Fese is the simplest iron based superconductor but with the diverse properties. Pdf superconductivity in the iron selenide kxfe2se2 0. Here we report on the optimization of synthesis of iron selenide based superconducting powders and the fabrication of selenide based wire. The parent liohfese phase of lithium iron hydroxide. This superconductor exhibits a broad transition, reaching zero resistance at 10 k. Pdf magnetic softness in ironbased superconductors. Of all the iron based superconductors, alkali iron selenides a yfe 1. By intercalation of alkali metal ions into adjacent iron selenide layers, which induces more electrons into the fese layers, the t c can also be. Iron ii selenide occurs naturally as the niasstructure mineral achavalite. Fese with aluminum indicated the onset of superconductivity at 10. Superconductivity and magnetic properties of single crystals of k 0. Bulk iron selenide fese is a superconductor with a critical temperature tc 8 k, but superconductivity is substantially enhanced in singleunit cell films of fese grown on strontium titanate.
The phase diagram of the system fese reveals the existence of several nonstoichiometric phases between 49 at. By intercalation of alkali metal ions into adjacent ironselenide layers, which induces more electrons into the fese layers, the t c can also be. Synthesis and characterisation of novel superconductors core. We prepared highquality potassiumdoped iron selenide kxfe2yse2 thin films by molecular beam epitaxy and unambiguously demonstrated the existence of phase separation, which is currently under debate, in this material using. Synthesis of a new alkali metalorganic solvent intercalated iron. Superconductivity in the iron selenide k xfe 2se 2 0 x 1. Superconductivity in alkali metal intercalated iron. Phase separation and magnetic order in kdoped iron selenide superconductor. Previously most hightemperature superconductors were cuprates and being based on layers of.
The intercalation chemistry of layered iron chalcogenide. Coexistence of superconductivity and antiferromagnetism in. Previous experimental results have shown important differences between iron selenide and arsenide superconductors which seem to suggest that the hightemperature superconductivity in these two subgroups of iron based families may arise from different electronic ground states. The unexpected properties of alkali metal iron selenide superconductors. Evidence of superconductivityinduced phonon spectra. Superconductivity in the iron selenide kxfe2se2 0 iron based and copperbased superconductors, including high t c values, and proximity of a magnetically ordered state, suggest that the superconductivity in the febased materials is unconventional. We prepared highquality potassiumdoped iron selenide. Alkali metal intercalated iron selenide superconductors a x fe2y se2 where a k, rb, cs, tlk, and tlrb are characterized by several unique properties, which were not revealed in other.
Nov 27, 2011 the newly discovered alkalidoped iron selenide superconductors 1,2 not only reach a superconducting transition temperature as high as 32 k, but also exhibit unique characteristics that are absent. Such a singlelayer film can be viewed as a twodimensional system composed of weakly coupled twoleg iron ladders. Similar to the electronic properties of layered iron based superconductors 24, 25, the conducting electrons mainly come from the contribution of co 3d states partially hybrided with sb 5p states. Emergent states of matter taught by professor nigel goldenfeld at university of illinois at urbana. Pressureinduced insulatormetal transition and the pathway. Study reveals mysterious electronic signature of ironbased. As the materials cool, they undergo a slight structural shift. Fabrication, characterization and applications of iron selenide. New high t c ironselenide superconductor with hydroxide spacer. Lafeaso takes the zrsicuas structure filled pbfcl type 15 and contains antipbo or antifluoritetype feas layers in. Within just two months, physicists, mostly in china, had substituted other rareearth elements for lanthanum, found optimal electron and hole. Intertwined charge, spin, and pairing orders in doped iron ladders.
Phase separation and magnetic order in k doped iron selenide superconductor. The newly discovered alkalidoped iron selenide superconductors. Iron based arsenide1 and selenide superconductors are compounds where chemical control of the properties by isovalent or aliovalent substitution1. We prepare singlelayer potassiumdoped iron selenide 110 film by molecularbeam expitaxy.
Scanning tunneling spectroscopy reveals that superconductivity is developed in this twoleg ladder system. Highlytunable crystal structure and physical properties in. Iron selenide superconductors exhibit a number of unique characteristics that are helpful for understanding the mechanism of superconductivity in hightc iron based superconductors more generally. Superconductivity in the iron selenide kxfe2se2 0 x 1. Oct 19, 2020 typeii iron based superconductors fescs, the alkalimetalintercalated iron selenide a x fe 2. Temperature dependent local atomic displacements in ammonia. Superconductivity in fechalcogenide yao li may 12, 2018 submitted as term paper of phys 569. Alkali doped iron selenide is the latest member of high tc.
Recently, superconductivity was discovered at 32 k in a layered iron selenide, k 0. By performing firstprinciples electronic structure calculations and analyzing effective magnetic model of alkalidoped iron selenides, we show that the materials without iron vacancies should. Pdf superconductivity in a singlelayer alkalidoped. The superconducting gap is similar to that of the multilayer films. Dec 09, 2019 that waste could be eliminated by superconductivity the zeroresistance flow of electricity. Nov 15, 2014 for alkaline iron selenide superconductors studied in the current context, inelastic neutron scattering has revealed in insulating rb 0. The hightc alkali doped iron selenide superconductors kxfe2yse2 have been recently shown to be intrinsically phase separated into fe vacancy ordered block antiferromagnetic regions and. The alkalidoped iron selenide superconductors have generated considerable excitements as well as confusions, regarding the delicate interplay between fe vacancies, magnetism and superconductivity. In contrast to bulk iron selenide, which is a lowtemperature superconductor, a single layer of iron selenide on a doped strontiumtitanate substrate becomes a hightemperature superconductor, with a critical temperature in excess of 40 k.
Very recently, iops haihu wen and his collaborators synthesized the first member of what could become a new family. The band structure of iron selenide top is complex and typical of the other febased superconductors. It has also been found that some iron chalcogens superconduct. Iron selenides have emerged as an important class of iron based superconductor.
Jun 01, 2016 thus, since discovery in 2010 these compounds have attracted really a great interest and according to the research fronts 20 the topic alkalidoped iron selenide superconductors was the number one within the whole physics science. Those papers document a remarkable explosion of knowledge. Soon it was shown, that even though the chemical formula is relatively simple, the compounds exhibit very. One can picture it as a simple repetition of an fese plane, with two selayers sandwiching a square lattice of fe ions. Magnetization measurements reveal a superconducting shielding fraction. Alkalidoped iron selenide is the latest member of high tc. The stoichiometric superconducting phase kfe2se2 contains no iron. The unexpected properties of alkali metal iron selenide. Electric doublelayer transistor using layered iron selenide. Here we report the complete phase diagram of a newly synthesized superconducting sc system, li1xfexohfese, with. Previous experimental results have shown important differences between iron selenide and arsenide superconductors, which seem to suggest that the high temperature superconductivity in these two subgroups of iron based family may arise from different electronic ground states.
Pdf superconductivity in a singlelayer alkalidoped fese. Alkalidoped iron selenide is the latest member of high tc superconductor family, and its peculiar characters have immediately attracted extensive attention. Fabrication, characterization and applications of iron. Photoemission spectroscopy indicates that the substrate injects electrons into the iron selenide layer that bury the hole bands at the center of the. The newly discovered alkali doped iron selenide superconductors not only reach a superconducting transition temperature as high as 32 k, but. Superconductivity in a singlelayer alkalidoped fese. Hightc superconductivity in electrondoped iron selenide. Visualization of the electronic phase separation in. Superconductivity in alkali metal intercalated iron selenides. However, physicists have found it difficult to interpret and describe the behavior of unusual superconductors such as iron selenide. Structure and superconductivity of the layered iron.
Pdf impurityinduced subgap bound states in alkalidoped. Since hosonos discovery, preprints about them have appeared on the arxiv server at a nearsteady rate of 2. Phase separation and magnetic order in kdoped iron. The newly discovered alkalidoped iron selenide superconductors exhibit unique characters that are absent in other iron based superconductors, such as antiferromagnetically ordered insulating phases, extremely high neel transition temperatures, and the presence of fe vacancies and ordering. Scanning tunneling microscopy study of kdoped iron. Pdf block antiferromagnetism and checkerboard charge. May 21, 2019 in iron selenide and other iron based superconductors, iron atoms in the central 2d sheet are spaced in checkerboard fashion, exactly the same distance from one another in both the leftright direction and forwardback directions. The newly discovered alkalidoped iron selenide superconductors1,2 not only reach a superconducting transition temperature as high as 32 k, but also exhibit unique characteristics that are absent from other iron based superconductors, such as antiferromagnetically ordered insulating phases3,4, extremely high neel transition temperatures5,6 and. Fese is dependent on structural deformation, which can be achieved by different stoichiometric ratios and doping of fese sites. Study reveals mysterious electronic signature of iron. Temperature dependent local atomic displacements in.
It has a critical temperature t c of 8 k at normal pressure, and 36. Structure and composition of the superconducting phase in. The highlighted studies concern the bulk iron selenide fese fese, to be more precise 3, a member of the iron chalcogenide superconductors. The iron selenide superconductor has a formula of fe 1. Theory of twomagnon raman scattering in alkaline iron. Phase separation and magnetic order in kdoped iron selenide. Scanning tunneling microscopy study of kdoped iron selenide. First, the evolution of research into a certain type of material eventually calls for high quality thin lms of this material to. Kfe2se2 is the parent compound of kdoped iron selenide superconductors wei li,1 hao ding,1 zhi li,2 peng deng,1 kai chang,1 ke he,2 shuaihua ji,1 lili wang,2 xucun ma,2 jiangping hu,3 xi chen,1, and qikun xue1, 1state key laboratory of lowdimensional quantum physics, department of physics, tsinghua university, beijing 84, china 2institute of physics, chinese academy of sciences.
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