Polaronic conductivity in the photoinduced phase of 1T-TaS2

The transient optical conductivity of photoexcited 1T-TaS2 is determined over a three-order-of-magnitude frequency range. Prompt collapse and recovery of the Mott gap is observed. However, we find important differences between this transient metallic state and that seen across the thermally-driven insulator-metal transition. Suppressed low-frequency conductivity, Fano phonon lineshapes, and a mid-infrared absorption band point to polaronic transport. This is explained by noting that the photo-induced metallic state of 1T-TaS2 is one in which the Mott gap is melted but the lattice retains its low-temperature symmetry, a regime only accessible by photo-doping.Comment: 10 pages, 4 figure

University Physics Volume 2

University Physics is a three-volume collection that meets the scope and sequence requirements for two- and three-semester calculus-based physics courses. Volume 1 covers mechanics, sound, oscillations, and waves. Volume 2 covers thermodynamics, electricity and magnetism, and Volume 3 covers optics and modern physics. This textbook emphasizes connections between theory and application, making physics concepts interesting and accessible to students while maintaining the mathematical rigor inherent in the subject. Frequent, strong examples focus on how to approach a problem, how to work with the equations, and how to check and generalize the result.https://commons.erau.edu/oer-textbook/1002/thumbnail.jp

Raman studies of doped magnetite above and below the Verwey transition

The nature of the Verwey transition in magnetite (Fe3O4) remains an unsolved puzzle after more than 60 years. Impurities and dopants present in magnetite can alter the Verwey transition temperature T-v as well as other physical characteristics of magnetite. We present the results from Raman studies of Mn-, Ni-, and Al-doped magnetites with Verwey transition temperatures ranging from 115 to 123 K. Mn and Ni substitute only in the octahedral sites of magnetite's spinel structure, while Al has been shown to occupy both octahedral and tetrahedral sites. We analyze the shifts in the Raman spectra of our samples relative to stoichiometric and oxygen deficient magnetite. Substitution sites and concentration of dopants will be discussed. In particular we discuss changes in the A(1g) 668 cm(-1) and T-2g 538 cm(-1) modes due to doping. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067858

Enhanced morphological stability of silver nanoparticles supported on rough substrates at high temperatures

Noble metal nanostructures serve as excellent substrates for the detection of trace amounts of substances in surface enhanced Raman spectroscopy, but they have not found widespread commercial use due to their instability and short shelf lives. This work demonstrates that silver nanoparticles grown onto substrates with nanoscale roughness, using glancing angle physical vapour deposition and subsequently thermally annealed at 500°C to generate a stable lower energy configuration, exhibit Raman enhancements that are strong and remain stable with no drop over 30 days. These nanoparticle arrays may serve as time stable substrates for commercial scale Raman spectroscopy or may be employed in harsh environments

Enhanced morphological stability of silver nanoparticles supported on rough substrates at high temperatures

Noble metal nanostructures serve as excellent substrates for the detection of trace amounts of substances in surface enhanced Raman spectroscopy, but they have not found widespread commercial use due to their instability and short shelf lives. This work demonstrates that silver nanoparticles grown onto substrates with nanoscale roughness, using glancing angle physical vapour deposition and subsequently thermally annealed at 500°C to generate a stable lower energy configuration, exhibit Raman enhancements that are strong and remain stable with no drop over 30 days. These nanoparticle arrays may serve as time stable substrates for commercial scale Raman spectroscopy or may be employed in harsh environments

Degradation Mechanism of Ag Nanorods for Surface Enhanced Raman Spectroscopy

Abstract This paper reports a degradation mechanism of silver (Ag) nanorods that are used as substrates for surface enhanced Raman spectroscopy (SERS). The attachment of sulfur and hydrocarbons to the surfaces of Ag nanorods is observed when they are stored in ambient over four months. This attachment is observed to correlate with ~20% decrease in SERS signal. The attachment, and thereby the signal degradation, takes three weeks to complete, and remains stable after the initial decay over the rest of the four month test period. While this degradation mechanism is a limitation to the gross enhancement, the ensuing stability beyond three weeks is encouraging

Electrical resistance of single-crystal magnetite (Fe3O4) under quasi-hydrostatic pressures up to 100GPa

The pressure dependence of electrical resistance of single-crystal magnetite (Fe3O4) was measured under quasi-hydrostatic conditions to 100 GPa using low-temperature, megabar diamond-anvil cell techniques in order to gain insight into the anomalous behavior of this material that has been reported over the years in different high-pressure experiments. The measurements under nearly hydrostatic pressure conditions allowed us to detect the clear Verwey transition and the high-pressure structural phase. The appearance of a metallic ground state after the suppression of the Verwey transition around 20 GPa and the concomitant enhancement of the electrical resistance caused by the structural transformation to the high-pressure phase form reentrant semiconducting-metallic-semiconducting behavior, although the appearance of the metallic phase is highly sensitive to stress conditions and details of the measurement technique. (C) 2016 AIP Publishing LLC

New ligands for uranium complexation: A stable uranyl dimer bearing 2,6-diacetylpyridine dioxime

The synthesis, characterization, and stability study of the first uranium complex bearing 2,6-diacetylpyridine dioxime (dapdoH2) is reported. The dimeric complex [UO2(dapdoH)Cl]2 is stable in solution as shown by ESI-MS and NMR spectrometry, and its solid-state structure was further analyzed by X-ray crystallography, IR, Raman and luminescence studies