9,256 research outputs found
Effect of Kondo resonance on optical third harmonic generation
We use the method of dynamical mean field thoery, to study the effect of
Kondo resonance on optical third harmonic generation (THG) spectra of strongly
correlated systems across the metal-insulator transition. We find that THG
signals are proportional to the quasiparticle weight of the Kondo peak, and
are precursors of Mott-Hubbard gap formation.Comment: ICM 2006 (kyoto) proceedin
Gapless chiral excitons in thin films of topological insulators
In a nanoscopic thin film of a strong topological insulator (TI) the Coulomb
interaction in the channel that exchanges the two electrons with the same
chirality in two different planes of the slab takes advantage of the minus sign
resulting from such "exchange" and gives rise to a bound state between the
positive energy states in one surface and the negative energy states in the
opposite surfaces. Therefore particle and hole pairs in the {\em undoped} Dirac
cone of the TI thin film form an inter-surface spin-singlet state that lies
below the continuum of free particle-hole pairs. This mode is similar to the
excitons of semiconductors, albeit formed between the electron and hole pairs
from two different two-dimensional surfaces. For low-momenta the dispersion
relation characterizing this collective mode is linear. Experimental comparison
of two slabs with different thicknesses can capture the exponential dependence
of the present effect on the slab thickness.Comment: Comments are welcom
Phenomenology of - Oscillations Revisited
We revisit the phenomenology of - oscillations in the presence
of external magnetic fields, highlighting the role of spin. We show, contrary
to long-held belief, that the - transition rate need not be
suppressed, opening new opportunities for its empirical study.Comment: 15 pages, REVTeX; revised and rewritten to focus on SM spin-dependent
effects, conclusions persis
- …