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Michaeli, Karen

Publications and source records attributed to Michaeli, Karen.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Thermal and Thermoelectric Phenomena in Novel Naterials and Systems of Disordered and Interacting Electrons

The major goals of this project were: 1. To study thermal transport in systems of disordered electrons in the presence of the long-range Coulomb interaction, 2. To combine the Quantum Kinetic Equation approach with the Renormalization Group analysis of disordered interacting electrons for studying thermal transport near the Metal Insulator Transition, 3. To study thermal transport and thermopower in systems of disordered electrons in the presence of strong electron-electron collisions at intermediate temperatures, and 4. To study the effects of out of plane vibrations on the thermal transport in graphene.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Voltage-induced long-range coherent electron transfer through organic molecules

Biological structures rely on kinetically tuned charge transfer reactions for energy conversion, biocatalysis, and signaling as well as for oxidative damage repair. Unlike man-made electrical circuitry, which uses metals and semiconductors to direct current flow, charge transfer in living systems proceeds via biomolecules that are nominally insulating. Long-distance charge transport, which is observed routinely in nucleic acids, peptides, and proteins, is believed to arise from a sequence of thermally activated hopping steps. However, a growing number of experiments find limited temperature dependence for electron transfer over tens of nanometers. To account for these observations, we propose a temperature-independent mechanism based on the electric potential difference that builds up along the molecule as a precursor of electron transfer. Specifically, the voltage changes the nature of the electronic states away from being sharply localized so that efficient resonant tunneling across long distances becomes possible without thermal assistance. This mechanism is general and is expected to be operative in molecules where the electronic states densely fill a wide energy window (on the scale of electronvolts) above or below the gap between the highest-occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). We show that this effect can explain the temperature-independent charge transport through DNA and the strongly voltage-dependent currents that are measured through organic semiconductors and peptides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Electric Field-Controlled Magnetization in GaAs/AlGaAs Heterostructures–Chiral Organic Molecules Hybrids

Here, we study GaAs/AlGaAs devices hostinga two-dimensional electron gas and coated with a monolayer of chiral organic molecules.We observe clear signatures of room temperature magnetism, which is induced in these systems by applying a gate voltage. We explain this phenomenon as a consequence of the spin-polarized charges that are injectedinto the semiconductor through the chiral molecules. The orientation of the magnetic moment can be manipulated by low gate voltages, with a switching ratein the MHz range. Therefore, our devices implement an efficient, electric field controlled magnetization, which has long been desired for their technical prospects.

36 MATERIALS SCIENCE↗