Bulletin of the American Physical Society
2014 Annual Fall Meeting of the APS Prairie Section
Volume 59, Number 19
Friday–Saturday, November 21–22, 2014; Monmouth, Illinois
Session F1: Condensed Matter II |
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Chair: Kishor T. Kapale, Wester Illinois University Room: CSB 100 - Pattee Auditorium |
Saturday, November 22, 2014 3:50PM - 4:26PM |
F1.00001: London Penetration Depth Measurements in Iron-Based Superconductors Utilizing a Tunnel Diode Resonator Circuit Invited Speaker: Ryan Gordon Newly discovered iron-based superconductors may be the key to understanding how the general mechanism of high-temperature superconductivity is possible. One way to gain insight into how this phenomenon works is to experimentally probe the superconducting gap structure in these materials, which is closely tied to the electronic interactions that give rise to this state. The experimental probe that has been used in this study to look at the superconducting gap structure is the London penetration depth, which characterizes the rate at which externally applied magnetic fields are screened from the interior of a superconductor. The London penetration depth in various members of the iron-based superconductors has been measured in this study utilizing a tunnel diode resonator (TDR) circuit. This is a specially designed LC oscillating circuit that is powered by a tunnel diode with a radio frequency resonance having parts-per-billions sensitivity to sense changes in its natural resonance frequency induced by a sample. The resulting data for the iron-based superconductors will be shown and compared to other types of superconductors that have been measured with the same technique. [Preview Abstract] |
Saturday, November 22, 2014 4:26PM - 4:38PM |
F1.00002: Entanglement dynamics of capacitively coupled spin qubits in the presence of stray inductance Michael Wolfe, Shawna Chisholm, Jason Kestner A pair of spin qubits formed by electrons confined in a pair of double quantum dots can be entangled at distances on the order of microns via a floating metallic top gate that mediates capacitive coupling [1]. The double-well biases, and hence the coupling through the top gate, can be controlled through voltage leads connected to an arbitrary waveform generator. We theoretically examine how the entanglement dynamics of the system are affected by inductance of the coupling element when the biases are driven at high frequencies. We numerically simulate the von Neumann entropy of the reduced density matrix as a function of time in various parameter regimes. In particular, we examine the behavior when the qubits are driven near the resonance frequency of the coupling element. \\[4pt] [1] L. Trifunovic et al., Phys. Rev. X 2, 011006 (2012). [Preview Abstract] |
(Author Not Attending)
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F1.00003: \textit{in situ} Electron Holography for Electromagnetic Analysis at Nanoscale Arturo Ponce, Fernando Mendoza, Jesus Cantu, John Eder Sanchez Electron holography provides powerful information about not only morphology and size of individual nanostructures but electromagnetic behavior around and within the structures. Quantitative measurements can be done to characterize the magnetic and electric properties in these structures. In addition, be stimulating with external signals we can study their response and important characteristics of the structures. In the current work, the magnetic contribution of the objective lens in magnetic nanostructures studied under Lorentz conditions and by applying a magnetization reversal process. In addition, the active reception/transmission behavior of ZnO/Ag nanoantennas has been mapped simultaneously under an in-situ radio frequency signal by electron holography and phase reconstruction. Time evolution of the radiation pattern was recorded varying the amplitude from 0 to 5 volts and a modulated frequency from 1 to 10 MHz. The phase maps show the distribution of the electric field surrounding individual nanoantennas. This is the first evidence in which electron holography is used to study the multidirectional radiation pattern on an active nanoantenna element. [Preview Abstract] |
Saturday, November 22, 2014 4:50PM - 5:02PM |
F1.00004: Radiative Transition Probability and Stimulated Emission Cross Section of Sm$^{3+}$ Ions in Lead Borate Glasses William Heidorn, Saisudha Mallur, P.K. Babu We prepared as series of lead borate glasses with the composition xPbO:(99.5 - x)B$_{2}$O$_{3}$:0.5Sm$_{2}$O$_{3}$ (x $=$ 29.5 to 69.5 in steps of 10 mol{\%}) by using the melt quench technique followed by 3 hours of annealing near the glass transition temperature. Optical absorption and fluorescence spectra of Sm$^{3+}$ (RE) doped in lead borate glasses were analyzed using Judd-Ofelt theory. The compositional dependence of Judd-Ofelt intensity parameters, $\Omega _{\mathrm{t}}$ (t $=$ 2, 4, 6), were determined. $\Omega_{2}$ was found to decrease with increasing PbO concentration indicating a decrease in the asymmetry of the crystal field at the RE site and $\Omega _{6}$ was found to decrease with increasing PbO content indicating a change in the covalency of the RE-O bond. The intensity parameters were then used to calculate the radiative transition probability of the excited states. The stimulated emission cross section for the intense fluorescence transition (598 nm) calculated from the radiative transition probability shows a maximum value (4.5 $\times$ 10$^{-22}$ cm$^{2})$ for the base glass containing 49.5 mol{\%} PbO. [Preview Abstract] |
Saturday, November 22, 2014 5:02PM - 5:14PM |
F1.00005: Sub-nanoscale Microscopy via Coherent Population Oscillations Kishor Kapale, Girish Agarwal We present a microscopy scheme to attain sub-nanoscale resolution based on the phenomena of coherent population oscillation (CPO). We build on the success of our earlier super-resolution methods based the phenomena of coherent population trapping (CPT). For successful application to microscopy, the effect being employed for super-resolution needs to be attainable in a large class of materials. In this context, it becomes necessary to resort to a phenomena-which is similar to CPT but can be potentially observed in a larger class of materials including gases, liquids, and room-temperature solids--such as CPO. The CPO based schemes involve two-level atoms coupled to two optical fields slightly different in frequency. The CPT-like nonlinear effects such as group velocity manipulations within the CPO schemes have been observed in room temperature solids and biological samples as opposed to in atomic vapors and cold atomic gases in the case of CPT. This parallel allows us to extend our CPT-based work to CPO-based microscopy schemes and makes them attainable in much larger class of materials including solids and biological samples. We show that the CPO-based schemes offer similar resolution as the CPT-based schemes and are attainable in a larger class of materials. [Preview Abstract] |
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