Bulletin of the American Physical Society
Annual Meeting of the APS Four Corners Section
Volume 60, Number 11
Friday–Saturday, October 16–17, 2015; Tempe, Arizona
Session I4: Condensed Matter Physics IV |
Hide Abstracts |
Chair: Karine Chesnel, Brigham Young University Room: PSA103 |
Saturday, October 17, 2015 11:00AM - 11:12AM |
I4.00001: Vortex Rectification Resulting from Thickness Modulation in Superconducting Granular-Aluminum Films Weston Maughan, August DeMann, Stuart Field A periodic modulation in the thickness of superconducting granular-aluminum films can result in the rectification of vortex motion. In our experiments, vortices are driven in both directions across a sample and the resulting voltages are measured. differences in the voltages corresponding to motion in opposite directions imply that the vortices move more readily in one direction, leading to an overall \textit{rectification} in their motion. Measurements were taken at various applied magnetic fields and temperatures for flat reference films, symmetric films with a sinusoidal thickness modulation, and asymmetric films with a ``sawtooth'' thickness modulation. Clear rectification effects are observed; however, their interpretation is complicated by other sources of vortex pinning. In order to reduce pinning due to surface roughness, the samples were smoothed by argon ion bombardment. While smoothing the samples in this way has shown promising reductions in the background pinning, edge effects also appear to contribute to the rectification. In future work, we plan to suppress edge pinning by tapering or texturing the edges. [Preview Abstract] |
Saturday, October 17, 2015 11:12AM - 11:24AM |
I4.00002: Pattern formation in superheated cylindrical superconductors Alden Pack A hallmark of superconductivity is the Meissner effect: the expulsion of an externally applied magnetic field. For large magnetic fields, the superconductor transitions to either a normal metal (type I) or mixed state (type II). However, the Meissner state may persist as a meta-stable state up to a critical "super heating field". For type II superconductors, the Meissner state first becomes unstable to fluctuations that break the transverse symmetry of the system. This instability leads to interesting pattern formation dynamics connecting the Meissner state to the final mixed state of vortex arrays. We explore this transition by numerically solving the time-dependent Ginzburg-Landau equation in a cylindrical superconductor. We illustrate the Meissner effect, convergence to a steady state, quenching, and nontrivial dynamics characterizing vortex formation. [Preview Abstract] |
Saturday, October 17, 2015 11:24AM - 11:36AM |
I4.00003: Patterns Formed By Broad Ion Bombardment With Concurrent Matt Harrison, Mark Bradley The nanoscale patterns that spontaneously form when a material is subjected to bombardment by a broad ion beam have been a subject of great interest for many decades. This technique has the potential to be an extremely powerful and economical way of generating nanoscale structures for a myriad of applications. In this talk I will report recent theoretical results which show that rotating a binary sample during bombardment can change the characteristics of the resultant pattern significantly. [Preview Abstract] |
Saturday, October 17, 2015 11:36AM - 11:48AM |
I4.00004: Listening to Molecular Conversations with Infrared Nanoscale Imaging Benjamin Pollard, Markus Raschke Nanoscale composition underlies many properties of materials through a complex relationship between structure, molecular coupling, and the response of the material as a whole to light. Infrared imaging and/or spectroscopy are ideal tools for measuring those relationships, but they are limited by the diffraction limit to a spatial resolution of several micrometers. Scattering Scanning Near-field Optical Microscopy (s-SNOM) provides the ability to perform infrared imaging and spectroscopy beyond the diffraction limit, with nanometer resolution. In s-SNOM, light is focused onto the apex of a nanoscale metallic tip. We then detect the scattered light from the tip-sample interaction in the optical near-field of the sample’s surface. By scanning across the sample, we map out the s-SNOM signal with nanometer spatial resolution, enabling the measurement of nanoscale structure with sensitivity to chemical variations, crystallinity, molecular orientation, and coupling between molecules or neighboring domains. For example, we can map out the electric field variation within a single nanodomain of a block copolymer. Augmented by new light sources and engineered tips, it is possible to better probe the relationship between nanoscale composition and materials’ function. [Preview Abstract] |
Saturday, October 17, 2015 11:48AM - 12:12PM |
I4.00005: Spin-Polarized Current in a Superconductor Invited Speaker: Tingyong Chen Superconductivity is one of the most intriguing phenomena in nature. A certain metal becomes a superconductor below its critical temperature TC, loses electrical resistance, enables persistent current, and repels magnetic flux. Superconductivity occurs because electrons form Cooper pairs, which undergo Bose-Einstein condensation at TC. The binding of electrons into Cooper pairs causes a finite energy gap, which decreases with increasing temperatures and vanishes at TC. The intricate physics of superconductivity lies in the pairing mechanism and the symmetry of the energy gap. Most SCs are s-wave SCs with an isotropic superconducting gap. The high TC cuprates, due to an intriguing and still elusive pairing mechanism, are d-wave SCs with an anisotropic gap structure with nodes. The recent Fe p-nidtide SCs, not d-wave as first suspected, but s-wave albeit with an unconventional s\textpm pairing. The p-wave SCs, which were predicted in the BCS theory more than half a century ago, have proven to be very difficult for experimental confirmation. Superfluid He3 is the only known p-wave pairing in nature. The crucial feature of a p-wave SC is that the electrons in a Cooper pair can have the same spin orientation. This is very different from that of an s- or d-wave SC where electrons must have opposite spins in a Cooper pair. Thus a spin-polarized current can be injected into a p-wave SC but not an s- or d-wave SC. Using this technique, we first show that the Fe-superconductors, which have been predicted to be p-wave, are singlet SCs. Instead, I will show you another strong p-wave candidate. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700