文档介绍：Exciting New Insights into Strongly Correlated Oxides with puting: Solving a Microscopic Model for High Temperature Superconductivity
T. Maier, J. B. White, T. C. Schulthess (ORNL)
M. Jarrell (University of Cincinnati)
P. Kent (UT/JICS & ORNL)
What is superconductivity
Outline of this Talk
A model for high temperature superconductors
t
U
Algorithm and puting
1
2
2
1
1
1
1
2
2
2
2
1
New scientific insights and new opportunities
Electric Conduction in Normal Metals
In a perfect crystal
perfect conductor at T=0K
Real materials have defects
resistance finite at T=0K
at very low temperature metals
could e insulators (?)
(proposal by Kelvin, 1902)
While verifying Kelvin’s theory, Kamerling Onnes discovers superconductivity in Hg at 4K
Resistance in pure mercury (Hg)
drops to zero at liquid He temp.
Kamerling Onnes first to produce
liquid helium (He) in 1908
(Nobel prize in 1913)
Superconductor repels ic field
Meissner and Ochsenfeld, Berlin 1933
Superconducting state is a new phase with zero resistance and perfect ism
BCS Theory or “normal” superconductors:
Physical Review (1957), awarded Novel Prize in 1972
1950s: Bardeen Cooper and Schrieffer develop the theory of (conventional) superconductors
Phonon mediated attractive interaction: formation of Cooper Pairs
Coherence length of Cooper Pairs is ~ 10-4 cm
Superconducting state:
Cooper Pairs condense into macroscopic quantum state
~ 1023 particles are coherent!
But, at T>25K, lattice vibration destroy Cooper Pairs: fundamental upper limit for Tc
In 1986, Bednorz and Müller discover superconductivity in La5-xBaxCu5O5(3-y)
La5-xBaxCu5O5(3-y) with x=.75 has Tc~30K, normal state is poor conductor
pound, LaCuO2, is an insulator!
(Bednorz and Müller, Z. für Physik 1986, Nobel Prize 1987)
Something other than phonon mediate the formation of Cooper Pairs
Why modeling high temperature super-conductors is a challenge
We have to account for a macroscopic number of particles
The particle