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Chemical Synthesis of Magnetic Molecules

The discovery that transition-metal clusters can behave like tiny “magnets,” i.e. single-molecule magnets (SMMs), opens up the opportunity for their applications in information storage, quantum computing, and molecular spintronics devices. A major objective of our synthetic project is on the design and synthesis of such molecular nanomagnets, based on inorganic polyoxometalate ligands given the rigidity (which infers predictability) and diversity (which allows rational chemical design) of their ligand environments.

Metamaterials: Giving light another new twist, chirality

After years of doubt, the scientific community now embraces the almost paradoxical properties of metamaterials, also known as negative index materials (NIMs). The unusual properties of fabricated NIMs include perfect lensing (beating the diffraction limit for electromagnetic waves), zero reflectance, and negative Snell’s law angles. Acceptance of these phenomena has come with recent design, fabrication, demonstration, and detailed first principles simulations for operation at microwave and THz frequencies from the Ames Laboratory group.

Repulsive Casimir Force in Chiral Metamaterials

First predicted by distinguished Dutch physicist, H.B.G. Casimir in 1948, the Casimir force arises when two uncharged, parallel metallic plates are brought in close proximity. Noticeable at a distance of a few microns, this attracting force becomes dominant at a length scale of tens of nanometers. Classically, no force exists between the plates; the Casimir force is proportional to the surface’s area, a consequence of the quantum nature of the electromagnetic field. Not restricted to parallel plates, the Casimir force exists between any two objects for microscopic separations.

Rare Earth Alloys – Why Purity Matters

The use of the highest purity starting materials in fundamental research seems to be an obvious choice and is a priori assumed in experimental science, including rare earth metallurgy. Yet an ambiguous “99.9%” purity reported by commercial vendors for the rare earths, in almost all cases refers to the purity with respect to only the other rare earth elements, and generally does not include other metals and more importantly the presence of the interstitial non-metallic elements oxygen, nitrogen, hydrogen, and carbon.

Universal Dynamical Decoupling of a Single Solid-state Spin from a Spin Bath

We studied and implemented for the first time dynamical decoupling on a single solid-state spin, the spin of a nitrogen-vacancy (NV) center in diamond, and prolonged its coherence time by a factor of 25. Besides its fundamental importance, this achievement constitutes an important advance towards manipulating matter at the level of single spins and opens new possibilities for highly sensitive magnetic sensors, and possibly for qubits for larger scale quantum information processing.

Genetic Algorithm for Grain Boundary and Crystal Structure Predictions

We developed a global structure optimization method, genetic algorithm, for an efficient prediction of grain- boundary structures. Using this method, we predicted the most stable structures and a number of low-energy metastable structures for Si[001] symmetric tilted grain boundaries with various tilted angles. We show that most of the grain-boundary structures can be described by the structural unit model with the units being the dislocation cores and perfect-crystal fragments (see Fig. 1).

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