Theory of Condensed Matter Elbio Dagotto, Distinguished Professor, UT-ORNL. UT. Bulk (Mn,Cu oxides). Organization. UT. Strongly Correlated Electrons. Complex transition metal oxides (high temperature superconductors, manganites, etc) Oxides multilayers.
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Theory of Condensed Matter
Distinguished Professor, UT-ORNL
Bulk (Mn,Cu oxides)
Transport in nanoscopic systems.
(II) Fe superconductors (Adriana Moreo)
Materials where Coulombic
repulsion and strong e-ph
couplings play a key role.
NON-PERTURBATIVE METHODS NEEDED
Many competing tendencies leads to
electrons and spins
+ elastic energy
Techniques: Monte Carlo and/or T=0 optimization of classical variables. Exact diagonalization of fermions. CPU time grows like N4. Typical clusters ~ 100 sites.
Potential applications in read sensors,
but critical temperatures must increase.
Resistivity of Mn-oxides
changes by 10 orders of
magnitude at low T
C. Sen, G. Alvarez, E.D., PRL 98, 127202 (2007).
Resistance vs. temperature,
Monte Carlo simulations.
Shape very similar to CMR
Summary: CMR appears
in a tiny cluster! We can easily
ask “questions” to the computer.
Similar to experimental physics.
12x12, MC, JT distortions
same in the three phases
Phase competition, as in manganites.
Nanoscale inhomogeneities, as in manganites.
Giant responses, as in manganites.
True phase diagram
of cuprates in clean limit?
Recent STM results for BSCCO above Tc
(Gomes et al., Nature 447, 569 (2007))
80a x 80a
Region of SC clusters, as predicted by theory
New playground in SCES.
Many groups working on this
subject (see E. D., Science 318,
Ohtomo et al, Nature 419 (‘02)
See also Mannhart, Triscone,
Hwang, Tokura, Ramesh,
Yunoki et al., PRB78, 024405 (2008); PRB76, 064532 (2007). Dong et al.,
MC, DMRG, Poisson Eq.,…
LaMnO3/CaMnO3 layers. Both AF insulating, but combination is FM metallic.
Interactions are important at low T:
Kondo effect observed in molecules
with net spin (peak in conductance)
Nature 391, 156 (98); 417, 722 (02); 417, 725 (02);
Science 280, 567 (98); 281, 540 (98).
Current vs. time
Al-Hassanieh et al., PRB73,195304 (2006)
Time unit ~ 10 fs (10^-15) if t=0.1 eV
“1000” = 10 ps
Excitons in Mott insulators
and polymers, relevant for
Gonzalez, ED, PRL 2008)