HTc

[Mk]

What is the definiton of a high temperature superconductor otherwise known as Type II superconductors?

[ZapperZ]

"What is the definiton of a high temperature superconductor otherwise known as Type II superconductors?"

You need to be a bit careful here. High-Tc superconductors do not have the identical definition as "Type II" superconductors. There are plenty of Type II superconductors that are not high-Tc superconductors. It just happens that all high-Tc superconductors that we have discovered are type II also.

Originally, high-Tc superconductors are the cuprate superconductors first discovered by Bednorz and Mueller. Most people would put Tc of greater than 35K for something to be considered as "high". This number isn't arbitrary. It was originally thought (pre 1986) that this is the upper limit that phonon-mediated superconductivity can get to based on our understanding of conventional superconductors.

Currently, there are several "families" of compounds that may be considered as belonging to the "high-Tc" superconductors, in addition to the cuprates. This includes possibly the ruthenates (even though their Tc's are lower than 35K), and MgB2 compound that was discovered barely 2 years ago.

Zz.