Collaborators:

1
Disorder-Driven Metalic Behavior in Dirty Mott
Systems
Vladimir Dobrosavljevic Department of Physics
and National High Magnetic Field
Laboratory Florida State University
Collaborators Darko Tanaskovic (FSU) Maria
Carolina De Oliviera Aguiar (FSU-Rutgers) Andrei
Pastor (FSU) Branislav Nikolic (Delaware) Eduardo
Miranda (Brazil) Gabi Kotliar (Rutgers) Elihu
Abrahams (Rutgers)
Funding NHMFL/FSU NSF grants DMR-9974311
DMR-0234215
2
Insulator
3

The Good, the Bad, and the Ugly

• Experiment
• Sharp transition at T0
• Continuous transition

• Theoretical problems
• No small parameter
• No symmetry breaking
• Order parameter??

• A way out controlled expansion around d2?
  (LCD)
• Scaling theory of localizationinteraction, sigma
  model,
• Limitations
• (disordered) Fermi liquid, low temperatures,
  small critical region (?)
• No strong correlation effects, NFL, metastability
  (glass)

4
Friend or Foe???
Sir Neville Mott
P. W. Anderson
5
Applications Mott transition, heavy fermions
6
Half-Filled Hubbard Model Disorder

• Disorder
• impurity states fill Mott gap
• (favor metal?)
• Anderson localization
• (favor insulator?)

Disorder W
Metal
MOTT INSULATOR (hard gap)
Hubbard U
Coexistence (Temperature-dependent)
7
Disordered Metallic Phase Correlation-Induced
Screening of Randomness Tanaskovic, VD, Kotliar,
Abrahams PRL 91, 066603 (2003)
Choose disorder W U, reduce EF (ignore
localization CPA)

• Resistivity drop at low T
• temperature-dependent screening?
• Altshuler-Aronov, Finkelstein,..
• Das Sarma, Aleiner...

• Hartree-Fock theory
• weak T-dependence, only factor 2 drop
• (solve DMFT in H-F, similar as others)

Puzzle Hartree-Fock (RPA) screening
compressibility reduced when m large??!!
8
Disordered Metallic Phase Incoherent Transport
DeOliviera-Aguilar, Miranda, VD, Kotliar,
Abrahams Europhys. Lett.67, 226 (2004)

• Strong T-dependence,
• factor gt 10 drop!!!
• (solve full DMFT
• using IPT or slave bosons)
• Enhanced screening at low T
• due to correlations, even as
• compressibility is small
• (approach to Mott transition)
• Strong inelastic scattering
• at higher T

Experiments on MOSFETs
Theory
Scattering rate 1/?
T
T/TF

• Incoherent Fermi liquid (low T TF/m
  distribution of local coherence scales)
• (microscopic origin of decoherence?)

9
(VD, Pastor, Nikolic, Europhys. Lett. 62, 76
(2003))
10
(No Transcript)
11
E. MirandaV.D, PRL 86, 264 (2001) Reports on
Progress in Physics (2005)
12
DMFT Picture of the Anderson-Mott
Transition (DMFT localization V.D. G.
Kotliar, PRL 1997 in progress)
Mott-like order parameter Typical quasiparticle
weight Z 1/m
Fraction of electrons turn into local moments
13
DMFT-TMT Picture of the Anderson-Mott
Transition VD, Pastor, Nikolic, Europhys. Lett.
62, 76 (2003)
Byczuk, Hofstetter, Vollhardt, PRL 2004 NRG
impurity solver
Electronic Griffiths Phase
Disorder W
Anomalous metallic phase sandwiched between Mott
and Anderson insulators
14
It takes all the running you CAN do, simply to
stay in one place From Alice in
Wonderland as quoted by P.W. Anderson in his
Nobel Lecture
Sir Neville Mott
P. W. Anderson
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Conclusions

• Extended DMFT order-parameter theory for
  Anderson-Mott transition
• Non-perturbative approach to correlations in
  disordered systems
• Non-Fermi liquid behavior as precursor to MIT
  two-fluid behavior
• Intermediate bad-metal phase between Anderson and
  Mott insulators
• New physical picture of MIT in correlated
  disordered systems
• Whats missing? Lots!