Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ferromagnetic Kondo Effect at Nanocontacts   Magnetic impurities bridging nanocontacts and break junctions of nearly
magnetic metals may lead to permanent moments, analogous to the giant moments
well known in the bulk case. A numerical renormalization group (NRG) study
shows that, contrary to mean field based expectations, a permanent moment never
arises within an Anderson model, which invariably leads to strong Kondo
screening. By including in the model an additional ferromagnetic exchange
coupling between leads and impurity, the NRG may instead stabilize a permanent
moment through a ferromagnetic Kondo effect. The resulting state is a
rotationally invariant spin, which differs profoundly from mean field. A sign
inversion of the zero-bias anomaly and other spectroscopic signatures of the
switch from regular to ferromagnetic Kondo are outlined.

5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex