Wednesday, August 29, 2007

Claudio Castellani: Superconductivity near a multiband Mott transition


Claudio Castellani introduced a DMFT toy model, motivated by the
fullerenes in order to describe the emergence of superconductivity
near a multiband Mott transition.

Claudio began his talk by briefly reviewing the effects of strong
electronic correlations on superconductivity. He pointed out that
there are two opposing effects. First, correlations reduce he
spectral weight of the electronic states (with quasi particle weight
Z<1) and hence reduce the electronic band width from W to Z*W. This
in turn leads to an increase in the density of states from rho to
rho/Z, which should give rise to an increase in Tc. On the other
hand, the attractive pairing potential, V, is reduced to V * Z^2,
which implies a reduction in Tc. Hence, in order to increase Tc
through strong correlations, it is necessary to increase the density
of states without a reduction in the pairing potential.

Claudio then introduced a 2-band Hubbard model with interorbital J,
whose ground state possesses 2 electrons per site (Claudio also
mentioned its relation to the 2 orbital Kondo-model). Since this J
gives rise to the formation of on-site singlets, this model allows
one to study superconductivity in an RVB environment. However, the
symmetry of the resulting superconducting state is s-wave, and hence
this is not a model for the cuprate superconductors, but is likely
more applicable to the fullerenes. Claudio studied this model by
using dynamical mean-field theory (DMFT).

Claudio identified a quantum critical point of the model which
separates a Fermi-liquid regime from a pseudo-gap phase. In the
vicinity of the QCP, the superconducting Tc is enhanced, and the
physical behavior of the system is determined by two energy scales,
that of the pseudogap and that of the SC gap. For large J, Claudio
found the uusual Migdal-Eliashberg type of reduction of Tc, while
for small J, the superconducting Tc is enhanced by the Coulomb U.
Claudio pointed out that there is a Drude weight gain in the SC
state, but that in the metallic state, the Drude weight goes to zero
before the QCP is reached. Claudio identified the pseudogap state as
an unstable metallic phase.

Last, Claudio raised the question of whether superconductivity is an
instability of the pseudogap, or whether these two have no relations
at all. He stated that the processes leading ot the pseudo gap are
not competing with pairing but with coherence, in analogy with
non-pairbreaking impurities in conventional superconductors.

Thilo Kopp asked whether other interactions (besides the
interorbital J) are included in this model, which Claudio confirmed.

Catherine Pepin asked how one can make any statements about the
Kondo physics of this model within single-site DMFT. Claudio
answered that this is possible since the model is a 2 orbital Kondo
model, in which the QCP separates the Kondo-screened phase from the
unscreened phase.

23 comments:

viagra online said...

I read that Claudio Castellani is expert of superconductivity! A friend of mine met him in a conference in his collegue!

Invertir en oro said...

Thanks for sharing this info because is very good and i like to post like this.

Increase penis size pills said...

Claudio Castellani is a great guy and the theories he mentions are based on good math.

premature ejaculation cure said...

The Superconductivity theory is very hard to understand by the lesser people.

Hieu Nguyen Ngoc said...

Welcome to our Gallery of London's elite escorts. We are regularly updating the site so please check back daily for new additions. Please enjoy browsing and feel free to call or email us if you have any questions or require any advice in selecting your perfect companion.
sex chatLondon Escorts

Sizegenetics cock extension device said...

Wow this claudio guy seems to have done a lot of work in his expertise field. I hope he had success in every thing he did.

Premature ejaculation Cure said...

Claudio's wor on superconductivity is really applaudable and he is one of the geniuses of all times.... thanks alot for sharing this wonderful post with us...

Prosolution Gel sexual enhancement gel review said...

I think the Superconductivity theory is very hard to understand by the weaker people....please be more specific...:)

pagg stack said...

Wow it seems like he has done a lot in the field of superconductivity.

pharmacy said...

This is perfect because I realize this man is a genius specially because no other scientist had the perfect idea to apply this theory of conductivity, I want to learn more about it.

xl pharmacy said...

It is new to me. I would like to read his article about it. I think that it is a pretty interesting approach.

muebles en pozuelo said...

Thanks so much for the post, quite helpful piece of writing.

Ideas de negocios said...

Thanks for taking the time to discuss this, but I am firmly convinced of this and love to learn more about the subject. If possible, acquire knowledge, would you update your blog with more information? It is very helpful to me

Buy domain name in India said...

Good guide about domain name registration. Really this is a new and different topic to me because I didn't heard about history of domain name registration. Thanks for sharing...

blogcar said...

I did a blog post about how I realized Search plus Your World would make search better.
escort sydneyprodutos eroticos

sex shop said...

This won't have effect in reality, that's exactly what I think.

Anonymous said...

Thanks for sharing this info because is very good and i like to post like this.
p spot stimulatorsLesbiskt porrfilm

whatlivemom said...

Just checked out Revolver , starring Jason Statham and Ray Liotta. It's streaming, and if you liked Snatch , then I would definitely recommend it. It's a whole lot more cerebral, and far less funny, but Guy Ritchie can't do anything without a little of the funny. It has a whole lot of bang-bang, and Jason Statham kicks far less ass than usual, but it's actually a movie that you'll end up talking about.

novelle fræk

Gold Coast Escorts

price per head call center said...

I really admire this, I mean it really looks interesting! Very nice write up. Anyways, its a Great post

London Crumpet said...

London escorts directory London Crumpet is created to expose Independent escorts and escort agencies in London. Everybody can post their advert on this directory for FREE.

London Asian Escorts said...

London Asian Escorts is an Asian and Oriental escort agency operating in Central London. The agency provides escort service for a true gentlemen.

Anonymous said...

order xanax xanax dosage milligrams - what's considered overdose xanax

Anonymous said...

where can i buy xanax online legally up your xanax dosage - blue round generic xanax