Overview of the Complex Materials Systems Cluster

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Overview of the Complex Materials Systems Cluster

• Whos in this cluster? Lance Cooper, Paul
  Goldbart, Duane Johnson, Richard Martin, David
  Payne, Myron Salamon, Ralph Simmons, Charlie
  Slichter, Dale Van Harlingen, Jim Wolfe, Ali
  Yazdani
• Whats in this talk
• Broad picture of the clusters research
• A (small!) handful of highlights
• See also Johnson, Yazdani Van Harlingen
  talksclusters posters, too

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Complex Materials Systems ClusterBroad picture
of clusters research

• Basic states of matter rather well developed by
  now
• metallic, insulating, magnetic,
  superconducting,...
• Due to specific dominant interactions
• Major current frontier
• complex states as subtle resolutions of competing
  interactions (magnetic, electric,
  superconducting,)
• Emergent states with exotic properties
• colossal-X, charge orbital order, HTSC,
  pseudo-gap, piezoelectrics, ferroelectrics,
  mesoscale order, strong coupled responses
• Strongly interacting particles, often of
  several brands
• creative approaches mandatory
• Broad nanoscience implications (explicitly
  implicitly)

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Magnetic perovskites structure states
La1-xCaxMnO3 crystal structure
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Complex Materials Systems ClusterBroad picture
of clusters research

• How do we attack this broad area?
• Range of complementary experimentsCooper, Payne,
  Salamon, Simmons,Slichter,Van Harlingen, Wolfe,
  Yazdani
• Theory, computation modelingGoldbart, Johnson,
  Martin
• Collaborations interactionsintra-
  inter-cluster beyond, including other DOE labs
  elsewhere
• Extensive use of MRL central facilities

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Complex Materials Cluster a few highlights

• Probing emergent regimes responses in complex
  oxides
• ordering at mesoscales
• quantum phase transitions
• magnetic influences on charge-carrier motion
• ferro- piezo-electrics electro-thermal imaging
  
• scanning probe spectroscopies
• Cooper, Goldbart, Martin, Payne,
  Salamon,Slichter, Van Harlingen, Yazdani
• Predicting manipulating structure in complex
  materials nanostructures
• Johnson, Martin, Yazdani
• Novel dynamics of model systems
• Simmons, Wolfe

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Underdoped YBCO Nanowires Evidence for Charge
Stripe Domains Van Harlingen group, interacting
with Goldbart, Yazdani others

• Motivation
• Microscopic origin of HTSC parent normal state
  remain elusive
• Prominent idea normal state has mesoscale
  charge-order
• fleeting organization of charge into stripes
• stripe orientations fluctuate in time
• Experimental approach
• Charge order gives resistance anisotropy (locally
  in space time)
• Impact enhanced in nanoscale samples (fewer
  domains)
• Nanofab of YBCO wires (FIB etching, photo-doping)
• Seeing telegraph noise in resistance
  (stripe-domain switching?)
• Now measuring anticorrelations in fluctuations of
  perp. resistances
• would provide evidence of fluctuating stripes
• More details on poster

width 200nm 5 stripe correl. lengths
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Exploring the Properties of Complex Materials
Under Extreme Conditions Cooper Chiang groups,
interacting with Salamon, Slichter, Yazdani
others

• Pressure- and field-tuned optical spectroscopy
  Powerful method for controlling studying
  exotic phases of complex materials at extreme
  temperatures, pressures magnetic fields
• Provides extensive insight into
• Relationship between exotic quantum phases
  (e.g., superconducting, charge-ordered,
  magnetic)
• Origin of colossal behavior (CMR pressure-
  field-induced transitions) often observed near
  complex phase boundaries

Quantum melting of a charge density wave
state Cooper Chiang groups, Phys. Rev. Lett.
(in press, 2003)
Pressure-tuned collapse of the Néel state Cooper
group, Phys. Rev. Lett. 89, 226401 (2003)
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Charge Transport as a Probe of Complex Magnetic
Oxides Salamon group, interacting with Cooper,
Goldbart, Slichter, Yazdani others

• Topological effects in magnetic materials
• hedgehog excitations in CrO2 PRL 89, 187201
  (2002)
• Anomalous Hall effect critical behavior of
  double perovskite Sr2FeMoO6
• find scaling with magnetization (with Goldbart
  group) PRB 64, 214407 (2001)

Experimental and theoretical (line) Hall effect
in CrO2
Hall conductivity of SFMOvs reduced
magnetization.
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Complex Materials Predictions from Electronic
Structure Calculations Martin group, interacting
with Johnson, Robinson Yazdani (experiments by
Robinson group)

• Goal Development application of efficient
  methods for computation of electronic structure
• Example 1
• Atomic-scale Au wires on Si (557) surface
• Predicted structure in very goodagreement with
  X-ray experi-ments (Robinson group)
• Explains anomalousfeatures of metallic
  bandsobserved via photoemission (Himpsel group,
  U. Wisconsin)
• Example 2
• Optical response of nanostructures smaller than
  opticalwavelengths (Na clusters, C-60,
  hydrogenated Si Geclusters)
• Comparison with experiments by Nayfeh group
  (UIUC)on hydrogenated Si clusters

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Complex Materials Theory and Computation Johnson
group (experiments by Nuzzo group)

• Goals
• Understand phenomena and predict properties in
  complex materials
• Interpret characterization data (from MRL, ANL,
  BNL,)
• Develop DFT methods for electronic, structural
  and thermodynamic properties
• Advance new multi-timescale dynamics modeling
  approaches
• see Fridays talk Theory and Simulation
• Example 1
• Reliable thermodynamics and partial order in
  multi-component alloys
• E.g., optimally truncated cluster expansions to
  predict phases, structures and characterization
  data ordering in Ni3V and hcp precipitation in
  fcc Al-Ag
• Example 2
• Self-assembly nanostructures on supports
• E.g., bi-metallic Pt-Ru catalytic nano-assemblies
  on carbon supports

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Nano-Assemblies on Supports Johnson group
(experiments by Nuzzo group)

• General issues
• Functional devices often require supports
• But properties can be dictated by these, possibly
  (semi-) periodic, interfaces
• catalytic properties not like bulk (e.g., Au
  catalytic only for lt 100 atoms)
• such cases need interface of quantum chemistry
  and solid-state physics
• Example
• Pt-Ru nanoclusters on carbon via metallo-organic
  chemistry
• All structural properties of clusters are
  support-mediated
• structures of cluster not commensurate with
  support
• experimental bond distributions and structure
  confirmed by theory
• theory provides understanding for control of
  properties
• catalytic Pt segregates from electronic size
  effect

Johnson, Nuzzo, Frenkel(Yeshiva/BNL), to be
submitted
Judith Yang (Pitt) Dark Field images from
PtRu5/C (carbon black)
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Kinetics of Excitons in the Semiconductor
Cu2O Wolfe group
Augerrate
Temperaturedependence

• Motivation
• Study relaxation processes in Cu2O
• Assess feasibility of making novel state of
  matter
• a Bose-Einstein condensate of excitons
• Approach
• Picosecond time- space-resolved
  photoluminescence (using MRL Laser Lab)
• Key issues temperature- strain-dependence of
• ortho-to-para down-conversion rates
• Auger recombination rates
• These experimental parameters are central to
  assessingcondensate feasibility

60 220 K
Strain confinement
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Pb(Mg1/3Nb2/3)O3-PbTiO3 Ferroelectricity,
Piezoelectricity Electro-thermal Imaging Payne
group, collaborating with Zuo others

• Single crystal PMN-PT
• huge piezo response
• strain coefficient 2-6000 pm/V
• electro-mechanical coupling gt 0.94
• energy conversion 90
• Electro-thermal imaging of polarization reversal
• remote sensing and direct observations of poling
• Ta2O5-based ceramics
• very high dielectric constant materials

PR
-EC
-PR
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Probing Electron Waves on the Nanoscale in
Complex Materials Yazdani grp, interacting w/
Cooper, Goldbart, Van Harlingen, Martin, Salamon,
Slichter others

• Goals
• Develop advanced tools for probing electronic
  material at the nanoscale
• Direct imaging of electronic states with
  state-of-the-art STMs (wide temp. mag. field
  ranges)
• Spectroscopic characterization of electronic
  states responsible for novel properties
• Manipulation of materials one atom at a time
• Combine theory and experiment to build a local
  perspective of complex electronic behavior

Electrons in Hybrid Nanostructures
Electron Waves in Complex Oxides
Fourier Transform Spectroscopy
See Yazdanistalk and poster
Feb.1st, 2002