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PHYSIQUE MESOSCOPIQUE
IPCMS - DMONS
Rodolfo Jalabert
Dietmar Weinmann
Post-docs: Jérôme Roccia (DMONS-DON)
Guillaume Weick
Etudiants: Guido Intronati (Strasbourg – Buenos Aires)
Wojciech Szewc
Domaines de recherche :
Conductance à travers de systèmes
fortement corrélés
Relaxation du spin
Transport dépendant de spin
Nanoparticules métalliques
Electronique moléculaire (G.W.)
Courants permanents et interactions (D.W.)
Décohérence et dissipation (R.J.)
Conductance à travers de systèmes
fortement corrélés
Quantum transport
universality
non-local
effects
interactions
individual object
nano
size
Landauer: conductance from scattering
Two terminal conductance:
- Separation of sample, leads and reservoirs
- Mean field, quasi-particle scattering states at the Fermi energy
- Equilibration in the reservoirs leads to dissipation
- Contact resistance
Conductance through an interacting region
- Is the scattering approach still valid ?
without inelastic process (zero temperature)
embedding method
- How do we calculate the transmission coefficient T ?
persistent current for interacting regionGround-state
+ leads
property!
Numerical implementation
Conductance through a correlated region
g decreases with U
W=0
g decreases with LS
Mott insulator
g ≈ 1 for LS odd
Perfect conductance only with adiabatic contacts
Even-odd asymmetry and Coulomb blockade
LS odd: Resonance NS
NS +1 electrons
in the interacting region
Coulomb
blockade resonance (half filling)
LS even: Transport involves charging energy U
Interacting region is a barrier
Observation of a parity oscillation in the conductance of atomic wires:
R.H.M. Smit, et al, PRL ’03
Fabry-Perot interference in a nanotube electron waveguide
Llang, et al, Nature ’01.
Can we describe an interacting region by
an effective one-particle scatterer?
R = R+ + R-
ohmic composition
Quantum mechanics, non-locality
S+
S-
R ≠ R+ + RS = S+ * SElectron-electron interactions
S ≠ S+ * S-
non local effect !
Interaction-induced non-local effects
universal correction!
0.7 anomaly
D.A. Wharam et al, J. Phys. C, 1988
M.A. Topinka et al, Nature, 2001
Conductance quantization
in a point contact
Nanoparticules métalliques
MIE THEORY
On the color of gold colloids - 1908
λ >> 2a
in a metal:
resonance pour
surface plasmon
Plasmon resonance in free clusters
(visible)
Bréchignac et al, PRL 1993
Photo-absorption cross
section of 12C nucleus
TIME RESOLVED EXPERIMENTS, POMP-PROBE
Differential transmission
(ps)
(eV)
ps
ps
ps
ps
correlated
scattering
energyelectrons
transfer
e-ee-phonons
& e-surface
scattering,
collective
modes
relaxation
tomatrix
the lattice
to the
thermal
distribution
nonthermal
cooling
of theregime
distribution
Bigot et al., Chem. Phys., 2000
COLLECTIVE AND RELATIVE COORDINATES
relative coordinates: mean field
center of
mass: harmonic
oscillator
One-particle
potential:
uniform jellium
background with
a
plasmon
Coulomb tail
coupling: dipole field
SIZE-OSCILLATIONS OF THE LINEWIDTH
Drude, τ‾1
confinement,
a < τ vF
Kawabata &
Kubo, 1966
Na
Semiclassical approach
Nonmonotonic
behavior !!
Time-Dependent Local
Density Approximation
PLASMON AS A COLLECTIVE EXCITATION
RPA eigenenergies :
restricted subspace
Plasmon = superposition of
low-energy e-h coupled to
high-energy e-h
additional subspace
SPIN DIPOLE EXCITATION
dipole absorption cross-section
Décohérence et dissipation
Spin echo
(Hahn)
H  -H
Loschmidt echo (fidelity) in the presence of a
weak coupling to the environment
|yH(t)
|yH0(t)
-H
|yH0 , -H (2t)
H
H0
H0
|y0
|yH0(t)
H=H0+S
|y0
environment
M(t) = |y0| exp[+i(H0+S)t] exp[-iH0t] |y0|2
How does M(t) depend on H0 , S , and t ?
Time-reversal
focusing
C. Draeger, M. Fink, PRL 1997