Seminar on Thursday, 2 December

[ivanisse]

CONDENSED MATTER AND STATISTICAL PHYSICS SECTION

	
SEMINAR on
Disorder and strong electron correlations


Thursday, 2 December   -  11:30 a.m.

Luigi Stasi Seminar Room,  Leonardo Building - first floor


Michele FABRIZIO  ( SISSA )


"Ferromagnetic Kondo at nanocontacts of nearly magnetic metals?"


Abstract

The word "Kondo effect" was originally coined to indicate the behavior 
of magnetic alloys, but nowadays it is invoked, not always properly, 
Anytime a zero-bias anomaly is observed in the tunneling spectrum across 
a nanocontact. There is by now plenty of evidence of the conventional 
fully-screened Kondo effect in tunneling across quantum dots, single 
atoms and molecules. More recently, evidence of the so-called 
underscreened Kondo effect, an unusual phenomenon in magnetic alloys, 
has been also found in single-molecule transistors.

In this talk, I will consider the possibility that nanocontacts could 
realize another phenomenon known to arise in magnetic alloys: the 
so-called "giant moment". Indeed, while e.g. Fe diluted in Ag or Cu is 
known to undergo perfect Kondo screening, when diluted in Pd or Pt it 
seems not only to retain its magnetic moment but also to induce locally 
in the host "giant moments" that eventually order ferromagnetically at 
low temperature. In particular, I will briefly present what is meant by 
"giant moments", and review theoretical explanations of the absence of 
Kondo screening in these alloys, checking their validity by a Numerical 
Renormalization group calculation. The ultimate goal is to identify the 
key properties of these alloys and to use this knowledge to anticipate 
the signals of  "giant moments" in transport across nanocontacts.