Importance of diminished local structural distortions and magnetism in causing iron-based superconductivity
September 29, 2014 — By analyzing the role of structural variation and magnetism of Cu dopants in FeAs planes, researchers demonstrated that orthorhombic distortions that give strong spin-density-wave spin (SDW) fluctuations are detrimental to superconductivity in BaFe2As2. The results provide new information about the interplay between local composition, magnetism and superconductivity.
Metallic Glasses: Different Deformation Properties Underpinned by the Same Trigger
September 26, 2014 — A novel simulation approach demonstrates that a universal deformation trigger exists in metallic glasses and that the spatial organization of these triggers is closely related to the dynamics and stabilities of the system. This work demonstrates that a universal trigger initiates deformation and the organization of such triggers significantly affects bulk behavior.
Laser speckle analysis resolves mesoscale transitions
September 23, 2014 — An elegant experimental approach, which requires only simple and widely available equipment, provides previously inaccessible spatial and temporal resolution on coexisting electronic domains in a technologically promising transition-metal oxide.
Creating and Activating a Terahertz Nanorotor in Graphene
September 17, 2014 — Replacing a hexagonal ring of carbon atoms in a graphene layer with a silicon trimer results in a terahertz rotor (1012 rotations/sec) with low friction. This demonstrates that the ultimate miniaturization of a mechanical device (switch, oscillator, stirrer) down to a triangular arrangement of three atoms is possible.
Direct observation of ferroelectric field effect and oxygen vacancy screening at ferroelectric–metal interface
August 21, 2014 — Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) studies of ferroelectric–metal interfaces revealed two distinct polarization charge screening mechanisms, with oxygen vacancies compensating negative charge and electrons compensating positive charge.
Magnetic fluctuations are good for superconductivity
August 15, 2014 — Atomic scale measurements of the strength of the magnetic fluctuations in a series of iron-based superconductors were made using high- resolution electron spectroscopy. Surprisingly, the superconducting transition temperature was higher when the magnitude of the fluctuating iron magnetic moment or “spin” was larger.
Thermopower Enhancement in Designer Oxide Superlattices
August 12, 2014 — A layer-by-layer design of 2D oxide superlattices with precisely controlled interface compositions has improved the thermopower of oxide thermoelectrics by 300% compared to that of bulk counterparts. Controlling the 2D carrier density through a new materials design strategy is critical for developing highly efficient thermoelectrics.
Structure-dependent Properties Guide Catalyst Design for Oxygenates Conversion
August 06, 2014 — The catalytic transformation of oxygenates (i.e. aldehydes, alcohols, ketones) on metal oxides to generate value added products such as fuels and additives is of great importance industrially, yet is not well-understood. ORNL researchers have provided new insights into how oxygenates react on metal oxide particles with well-defined structures.
Pulsed Laser Deposition of Photoresponsive Two-Dimensional GaSe Nanosheet Networks
July 31, 2014 — Researchers demonstrated a pulsed laser deposition (PLD) approach to synthesize networks of interconnected metal chalcogenide (GaSe) nanosheets that exhibit high photoresponsivity.
Predictive calculations of cuprate magnetic properties
June 24, 2014 — Magnetic couplings in a realistic cuprate system have been correctly predicted for the first time with highly accurate Quantum Monte Carlo (QMC) calculations. Effective magnetic models of superconductivity (previously reliant on experiment) can now be derived with confidence from theory, which could lead to better fundamental predictions of superconductor behavior.