High-temperature superconductivity

About: High-temperature superconductivity is a research topic. Over the lifetime, 7263 publications have been published within this topic receiving 175377 citations. The topic is also known as: high-temperature superconductivity.

Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films

Abstract: The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.

High current density in bulk YBa2Cu3Ox superconductor

Abstract: A liquid phase processing method for the fabrication of bulk YBa2Cu3Ox superconductors with large current carrying capacity has been developed. Slow cooling through the peritectic transformation (1030–980 °C) has been shown to control the microstructure of these superconductors. A cooling rate of 1 °C/h in this temperature range has yielded a microstructure with long plate type, thick grains oriented over a wide area. Current density up to 18 500 A/cm2 has been obtained by continuous direct current measurements and in excess of 62 000 A/cm2 with pulse current of 10 ms duration and 75 000 A/cm2 using 1 ms pulse. The strong magnetic field dependence observed in sintered bulk 1‐2‐3 superconductors is also minimized to a large extent where a current density in excess of 37 000 A/cm2 is obtained in a field of 6000 G.

Superconductivity produced by electron doping in CuO 2 -layered compounds

Abstract: We have discovered that the Ce4+doping and subsequent annealing in reducing atmosphere give rise to 24-K superconductivity in the Nd2CuO4-type structure with sheets of Cu-O squares. In contrast to the previously reported high-Tccuprates, the charge carriers in the new superconductors are doped electrons, not holes; this was confirmed by the measurements of Hall and Seebeck coefficients as well as by chemical analysis of the effective copper valence. An anomalous dependence ofTcon the concentration of doped electrons is shown for these electron-doped superconducting cuprates.

Superconductivity in the rare-earth-free Tl–Ba–Cu–O system above liquid-nitrogen temperature

Abstract: The initial discovery by Bednorz and Muller1 of 35-K superconductivity in the La-Ba-Cu-O system has stimulated worldwide activity in searching for higher-temperature superconductors. Elemental substitution has proved to be most effective in raising transition temperature. Substitution of Sr for Ba has produced 40-K superconductivity2–5and substitution of Y for La has produced a new high-temperature superconductor with transition temperature above liquid-nitrogen temperature6. A class of superconducting compounds of the form RBa2Cu307-x has been explored by further substitutions of other rare earths (Y is considered in the rare-earth [RI category here) for Y7-13. To date, a rare earth, an alkaline earth, copper and oxygen have been required for all high-temperature superconductors14,15. (Zhanget al 14reported 90-K superconductivity in the Th-Ba-Pb(Zr)-Cu-O system. Panetal15reported 50-K superconductivity in the Y-Ba-Ag-O system. As Th is a member of the actinide series which belongs to the same Group 3B in the periodic table as the lanthanide series and Ag belongs to the same Group 1B as Cu, high-temperature supercon-ductors are still thought to be closed in the Group 3B—Group 2A-Group 1B—oxygen system. ) Only partial substitutions ha. e led to superconductors, but with no significant rise of transition tem-perature (the only exception is 40-K superconductivity in La2CuO4-x , refs 16, 17). Here we report superconductivity in the rare-earth-free TI-Ba-Cu-O system. We have obsened sharp drops of resistance starting above 90 K with zero resistance at 81 K in this system. Magnetic measurements have confirmed that these sharp drops of resistance in the TI-Ba-Cu-O samples origi-nate from superconductivity. The samples are stable in air for at least two months, and their preparation is easily reproduced.

Magnetic-field-induced charge-stripe order in the high-temperature superconductor YBa2Cu3Oy.

Abstract: Nuclear magnetic resonance measurements of the model high-temperature copper oxide superconductor YBa2Cu3Oy demonstrate that high magnetic fields induce charge order, without spin order, within the material's CuO2 planes. The observed charge order has characteristics similar to those of stripe-ordered copper oxides, in which electronic charges spontaneously organize themselves into 'stripes'. The charge order develops only when superconductivity fades away. This work suggests that stripes are more common objects in the cuprates than was thought. They seem to compete with superconductivity, although the tendency to form stripes may be a necessary ingredient of high temperature superconductivity. Electronic charges introduced in copper-oxide (CuO2) planes generate high-transition-temperature (Tc) superconductivity but, under special circumstances, they can also order into filaments called stripes1. Whether an underlying tendency towards charge order is present in all copper oxides and whether this has any relationship with superconductivity are, however, two highly controversial issues2,3. To uncover underlying electronic order, magnetic fields strong enough to destabilize superconductivity can be used. Such experiments, including quantum oscillations4,5,6 in YBa2Cu3Oy (an extremely clean copper oxide in which charge order has not until now been observed) have suggested that superconductivity competes with spin, rather than charge, order7,8,9. Here we report nuclear magnetic resonance measurements showing that high magnetic fields actually induce charge order, without spin order, in the CuO2 planes of YBa2Cu3Oy. The observed static, unidirectional, modulation of the charge density breaks translational symmetry, thus explaining quantum oscillation results, and we argue that it is most probably the same 4a-periodic modulation as in stripe-ordered copper oxides1. That it develops only when superconductivity fades away and near the same 1/8 hole doping as in La2−xBaxCuO4 (ref. 1) suggests that charge order, although visibly pinned by CuO chains in YBa2Cu3Oy, is an intrinsic propensity of the superconducting planes of high-Tc copper oxides.