High-temperature superconductivity

Summary

High-temperature superconductors (abbreviated high-Tc or HTS) are defined as materials with critical temperature (the temperature below which the material behaves as a superconductor) above , the boiling point of liquid nitrogen. They are only "high-temperature" relative to previously known superconductors, which function at even colder temperatures, close to absolute zero. The "high temperatures" are still far below ambient (room temperature), and therefore require cooling. The first break through of high-temperature superconductor was discovered in 1986 by IBM researchers Georg Bednorz and K. Alex Müller. Although the critical temperature is around , this new type of superconductor was readily modified by Ching-Wu Chu to make the first high-temperature superconductor with critical temperature . Bednorz and Müller were awarded the Nobel Prize in Physics in 1987 "for their important break-through in the discovery of superconductivity in ceramic materials". Most high-

Official source

https://en.wikipedia.org/wiki/High-temperature_superconductivity

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related publications (100)

Related publications

Related people (121)

Related people

Related units (46)

Related units

Related concepts (57)

Related concepts

Related courses (121)

Introduction to superconducting electronic applications and their material requirements, including the fundamental phenomenology of superconductors. Key applications and their material requirements: a) magnets; b) quantum metrology; c) quantum computation.

Solid State Physics IV provides a materials and experimental technique oriented introduction to the electronic and magnetic properties of strongly correlated electron systems. Established knowledge is complemented by current research trends, aiming to prepare the students for independent research.

This course will focus on the electron transport in semiconductors, with emphasis on the mesoscopic systems. The aim is to understand the transport of electrons in low dimensional systems, where even particles with statistics different than fermions and bosons will be discussed.

Related courses

Related lectures (298)

Related lectures

Though the high superconducting transition temperature (Tc) is the most interesting technological aspect of high temperature superconductors, the complex way in which the spin, lattice and electronic degrees of freedom interplay, makes them of the highest scientific interest. This is illustrated by their rich phase diagram characterized by a variety of exotic groundstate including; Mott insulating, pseudogap and high temperature superconductivity. One of the most serious barriers that has prevented our understanding of the mechanism of high temperature superconductors thus far is the lack of information on how low energy Landau quasiparticles result from an organization of real particles. This organization, often colloquially referred to as "dressing", is a fundamental general concept in physics that explains a variety of physical phenomena, such as exotic particle formations and phase transitions. The role of the lattice in this dressing is particularly controversial. Phonons are quanta of lattice vibration energy, and play a crucial role in conventional superconductivity. They provide an attractive interaction allowing the electrons to condensate in superconducting Cooper pairs. However, high temperature superconductivity in the cuprates in achieved through hole doping in an antiferromagnetic Mott insulator. In this case, the antiferromagnetic background, the strong coulomb repulsion and the anisotropic superconducting gap all suggest a marginal role of the phonons. In order to assess experimentally the exact role of the phonon, angle resolved photoemission spectroscopy (ARPES) is the weapon of choice given its unique ability to probe the electronic structure of solids in an energy- and momentum-resolved manner. In this thesis, I will use ARPES to characterize the various form of dressing of the quasiparticles in the high temperature superconductor from the Fermi level all the way to the valence band complex. I'll show that when combined with isotope substitution and inelastic x-rays scattering, the strong electron-phonon interaction can be probed in vivid details. This thesis presents three fundamental results. 1) Using the isotope effect, the important and unusual role of the phonon is demonstrated, as well as the strong interplay between the magnetic and phonic degrees of freedom. 2) Using inelastic scattering, the intriguing interplay between the Fermi surface and the bond stretching phonon is exposed. And 3) By exploring the ARPES data up to high energy, two new energy scales at high binding energy as well as the spectral waterfalls phenomenon are revealed. When all these new elements are considered together, they clearly show the need to consider simultaneously the spin, lattice, Fermi surface topology and electronic degrees of freedom. The spectacular progress in ARPES techniques over the past two decades was critical for these results, and I will present in this thesis our current effort in pushing the techniques even further. In particular I'll present my efforts in building a laser based ARPES setup with a hemispherical analyzer and a spin resolved time of flight analyzer.

EPFL2008

Studies on the Effect of Strain on the Electronic Properties of Ultra Thin Films of Superconducting Cuprates

Nathaniel Wooding

High Tc superconductivity in cuprates is still an unresolved topic, and one particular challenge is why in-plane compressive strain enhances Tc in ultra thin LSCO-214 films (< 40nm), whilst tensile strain diminishes it. Especially intriguing is whether altering this strain at a given doping has an effect on T* (pseudogap) or Tc (condensation/phase coherence). As the ratio between T* and Tc is so high, we systematically grew a series of BSCCO-2201 films by in house pulsed laser deposition (PLD), and then thoroughly analysed these films with X-Rays, four point resistivity measurements and XPS. We succeeded to induce strain into the films; however, the strain was lost in the annealing process necessary for superconductivity. Subsequently, we focused on LSCO-214 films, and grew a series of strained ultra thin films of this compound. While the films were superconducting, none of our samples showed enhanced superconduc- tivity, probably due to growth disorder.Therefore, we eventually studied high quality films grown by MBE from BNL. We used the low energy muon beamline at PSI to perform μSR studies on two different com- pressive strain states. The successful measurements of the penetration depth and Ginzburg- Landau parameter κ on ultra thin films of this type using low energy muons showed the benefits of this technique. As the 2 films were of different thicknesses, further studies need to be done to disentangle which observed effects are due to strain and/or variation in c-axis, and which are due solely to thickness. Our accumulated results and those of other groups, (notably Naito et. al. at NTT) on strain in LSCO-214 films, and the ensemble of data, including our study, indicate that most likely it is a phase coherence enhancement due to the in-plane compressive strain that raises the Tc. In summary, in addition to the succesful implementation of PLD heteroepitaxy, XRD analysis and ρ(T) studies of LSCO-214 films we were able to establish that: 1. Phase coherence is improved by in plane compressive strain, hence Tc enhancement 2. Tc also seems to scale with apical oxygen, as previously reported by H. Keller et. al., and local distortions around the copper-oxygen tetrahedra 3. Last but not least, we were even able to induce strain into BSCCO-2201 films, yet at present the full electronic properties of this system are neither measured nor under- stood. Finally, further systematic studies on μSR are proposed, and are indeed underway at PSI, to further elucidate the microscopic role of strain in the mechanism of high Tc superconductivity.

EPFL2013

Quench Detection and Protection of the HTS Insert Coils

Natalia Hanna Glowa

As a result of extremely high upper critical fields B_c2, high temperature superconductors (HTS) have the potential to be used as high field insert coils in magnet systems where the background field is provided by low temperature superconductors (LTS) with the aim of application of such systems for high energy physics, nuclear magnetic resonance and energy storage. Among the superconductors discovered in late 1980s, one that is widely studied is YBCO coated conductor (CC). Despite the advanced 2G conductor technology in recent years allowing for manufacturing of long lengths of YBCO CC, up to 1 km, the crucial issue in practical application of the hybrid systems with YBCO insert coil remain the quench detection and protection of the insert. Unlike in LTS magnets, the quench propagation in HTS is significantly slower, which makes quench detection and consecutively protection, very challenging. Following a new approach for quench protection a non-insulated HTS insert coil was manufactured at the CRPP. In case of quench, the current is expected to by-pass the normal zone and prevent the coil from a permanent damage. The idea of non-insulated free-standing coils has been already studied and brought promising results in terms of self-protection of such coils. However, in a hybrid system of LTS-HTS, the quench behaviour needs careful evaluation that includes magneto-thermo-electrical study. The objective of this work is to study and discuss the applicability of HTS insert coils (insulated and non-insulated) by addressing the issue of their quench detection and protection schemes. The starting point for the analysis is studying the existing design according to CRPP specifications taking into account various operating modes together with detection and protection schemes. Finally, general guidelines for the design of a successful LTS-HTS magnet system will be discussed.

EPFL2016

EPFL2008

Studies on the Effect of Strain on the Electronic Properties of Ultra Thin Films of Superconducting Cuprates

Nathaniel Wooding

EPFL2013