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DOE BES/DMS Frederick Seitz Materials Research Laboratory Overview of the Complex Materials Systems Cluster Who’s in this cluster? Lance Cooper, Paul Goldbart,

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Presentation on theme: "DOE BES/DMS Frederick Seitz Materials Research Laboratory Overview of the Complex Materials Systems Cluster Who’s in this cluster? Lance Cooper, Paul Goldbart,"— Presentation transcript:

1 DOE BES/DMS Frederick Seitz Materials Research Laboratory Overview of the Complex Materials Systems Cluster Who’s 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 What’s in this talk Broad picture of the cluster’s research A (small!) handful of highlights See also Johnson, Yazdani & Van Harlingen talks; cluster’s posters, too

2 DOE BES/DMS Frederick Seitz Materials Research Laboratory Complex Materials Systems Cluster: Broad picture of cluster’s 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)

3 DOE BES/DMS Frederick Seitz Materials Research Laboratory Magnetic perovskites: structure & states La 1-x Ca x MnO 3 crystal structure

4 DOE BES/DMS Frederick Seitz Materials Research Laboratory How do we attack this broad area? –Range of complementary experiments Cooper, Payne, Salamon, Simmons, Slichter,Van Harlingen, Wolfe, Yazdani –Theory, computation & modeling Goldbart, Johnson, Martin –Collaborations & interactions intra- & inter-cluster & beyond, including other DOE labs & elsewhere –Extensive use of MRL central facilities Complex Materials Systems Cluster: Broad picture of cluster’s research

5 DOE BES/DMS Frederick Seitz Materials Research Laboratory 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 Complex Materials Cluster: a few highlights

6 DOE BES/DMS Frederick Seitz Materials Research Laboratory 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

7 DOE BES/DMS Frederick Seitz Materials Research Laboratory Pressure-tuned collapse of the Néel state Cooper group, Phys. Rev. Lett. 89, 226401 (2003) Exploring the Properties of Complex Materials Under Extreme Conditions Cooper & Chiang groups, interacting with Salamon, Slichter, Yazdani & others Quantum “melting” of a charge density wave state Cooper & Chiang groups, Phys. Rev. Lett. (in press, 2003) scattered photon incident photon sample ruby chip gasket diamond anvils low T, high H cryostat Increasing Pressure ‘solid’ CDW ‘soft’ CDW melted CDW 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

8 DOE BES/DMS Frederick Seitz Materials Research Laboratory Topological effects in magnetic materials –hedgehog excitations in CrO 2 [PRL 89, 187201 (2002)] Anomalous Hall effect & critical behavior of double perovskite Sr 2 FeMoO 6 –find scaling with magnetization (with Goldbart group) [PRB 64, 214407 (2001)] Experimental and theoretical (line) Hall effect in CrO 2 Hall conductivity of SFMO vs reduced magnetization. Charge Transport as a Probe of Complex Magnetic Oxides Salamon group, interacting with Cooper, Goldbart, Slichter, Yazdani & others

9 DOE BES/DMS Frederick Seitz Materials Research Laboratory Exp Theory 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 good agreement with X-ray experi- ments (Robinson group) Explains anomalous features of metallic bands observed via photoemission (Himpsel group, U. Wisconsin) Example #2 Optical response of nanostructures smaller than optical wavelengths (Na clusters, C-60, hydrogenated Si & Ge clusters) Comparison with experiments by Nayfeh group (UIUC) on hydrogenated Si clusters Complex Materials: Predictions from Electronic Structure Calculations Martin group, interacting with Johnson, Robinson & Yazdani (experiments by Robinson group)

10 DOE BES/DMS Frederick Seitz Materials Research Laboratory 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 Friday’s 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 Ni 3 V 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 Complex Materials Theory and Computation Johnson group (experiments by Nuzzo group)

11 DOE BES/DMS Frederick Seitz Materials Research Laboratory 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 < 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 Judith Yang (Pitt): Dark Field images from [PtRu 5 ]/C (carbon black) [Johnson, Nuzzo, Frenkel (Yeshiva/BNL), to be submitted] Nano-Assemblies on Supports Johnson group (experiments by Nuzzo group)

12 DOE BES/DMS Frederick Seitz Materials Research Laboratory Kinetics of Excitons in the Semiconductor Cu 2 O Wolfe group Motivation Study relaxation processes in Cu 2 O 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 assessing condensate feasibility Tunable ps pulses Spectrometer Micro-channel plate PMT Photon counting Temperatured ependence 60 220 K Auger rate 1 cm laser Strain confinement

13 DOE BES/DMS Frederick Seitz Materials Research Laboratory Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 : 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 > 0.94 – energy conversion ~ 90% Electro-thermal imaging of polarization reversal – remote sensing and direct observations of poling Ta 2 O 5 -based ceramics – very high dielectric constant materials +P R -E C -P R

14 DOE BES/DMS Frederick Seitz Materials Research Laboratory Fourier Transform Spectroscopy Probing Electron Waves on the Nanoscale in Complex Materials Yazdani grp, interacting w/ Cooper, Goldbart, Van Harlingen, Martin, Salamon, Slichter & others Feb.1 st, 2002 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 NanostructuresElectron Waves in Complex Oxides See Yazdani’s talk and poster


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