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.
Distinguished Professor, UT-ORNL
Bulk (Mn,Cu oxides)Organization
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
+ 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.
but critical temperatures must increase.(I.a) Colossal Magneto Resistance (CMR)
Resistivity of Mn-oxides
changes by 10 orders of
magnitude at low T
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 phasesMultiferroic manganites can also be studied S. Dong, et al., PRB 78, 155121 (2008)
Phase competition, as in manganites.
Nanoscale inhomogeneities, as in manganites.
Giant responses, as in manganites.
structure.High Temperature Superconductors
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,
Okamoto, …Correlated electron multilayers:Applications of complex oxides?Oxide electronics?
MC, DMRG, Poisson Eq.,…
LaMnO3/CaMnO3 layers. Both AF insulating, but combination is FM metallic.
Interactions are important at low T: Dong et al.,
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).(I.c) Effects of strong interactions in molecular conductors and QDs
Current vs. time Dong et al.,Transport in SCES systems (t-DMRG, S. R. White and A. Feiguin 2004)
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)