High-temperature superconductivity Is high-temperature superconductivity explained with the same argument as the low temperature one? What is the maximum temperature reached? What about Room-temperature superconductors?
 A: There is no such thing (yet) as a room temperature superconductor. The highest temperature superconductor (hydrogen sulfide, $\rm H_2S$, under high pressure) is still around $-70\rm^\circ C$.
Not all superconductors are explained with the same theory. Low temperature superconductors are usually explained by the BCS theory, which fails for many high temperature superconductors.
There are various theories that predict that various materials at extremely high pressures may be superconducting at room temperature (metallic hydrogen, for instance), but as of yet none is definitively confirmed.
A: I would like to answer on “Is high-temperature superconductivity explained with the same argument as the low temperature one?”. The low temperature superconductivity was explained by BCS theory which was built on electron-phonon interaction. However, most scientists have believed that high-temperature (high-T_c) superconductivity is not accounted for by the BCS theory, because the upper T_c = 28 K in the BCS theory was calculated by McMillan [Physical Review 167 (2), 1968 p 331-344]. Since the discovery of a cuprate high-T_c superconductor in 1986, many scientists have tried to reveal the high-T_c mechanism except the BCS theory. 
On the contrary, we have suggested that the BCS theory can also explain the high T_c in cuprate superconductors. The suggestion is based on that (1) high-T_c superconductivity appears in two dimensional CuO_2 plane, and that (2) the effective mass regarded as two dimensional density of states diverges near the quantum critical point (insulator-metal-transition point), and that (3) the intrinsic superconducting gap is formed at node as a small gap; these were not included in McMillan’s calculations. This is in detail given in “Why-does-BCS-theory-fail-to-explain-superconductivity-at-high-temperatures”. Moreover, the highest temperature superconductor (hydrogen sulfide, H3S, under high pressure) known as around 203 K has a conventional isotope effect as demonstrated by doping the H with D [nature 525 (2015) 73]. Thus, it is clearly a conventional BCS superconductor. 
In conclusion, high-T_c superconductivity can be explained in the context of BCS theory. May 20, 2018.
