Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for +publisher:"Colorado State University" +contributor:("Field, Stuart B."). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Colorado State University

1. Maughan, Weston F., II. Vortex rectification and phase slips in superconducting granular aluminum.

Degree: PhD, Physics, 2020, Colorado State University

Superconductivity is a unique and interesting phenomenon that manifests as a new phase of matter in a wide variety of materials. The most well-known property of superconductors is that they exhibit perfect conductivity when cooled below a critical temperature Tc. In addition to their perfect conductivity, superconductors exhibit the equally fundamental Meissner effect that expels magnetic fields from the interior of the material. While applications of a material that exhibits perfect conductivity, such as generating large magnetic fields via electromagnets or transmitting a large current with zero dissipation, are highly desired, the subtle details of flux penetration into mesoscopic samples may also be exploited to realize useful devices, or as a testbed to understand one-dimensional superconductivity. In this work, the nature of superconductivity in granular aluminum was explored in two mesoscopic sample classes: first, by studying Abrikosov vortices in films, and then by studying dissipation from phase slips in one-dimensional nanowires. The penetration of an applied field is possible in film sample geometries, even though the Meissner effect generally expels flux. This penetration occurs in type-II superconductors via quantized flux bundles through normal regions or domains of the superconductor called vortices. The behavior and dynamics of these vortices are of significant interest as they can be exploited to realize fluxonic devices that perform circuit operations analogous to the operations performed with electrons in electronics. One method to influence the motion of vortices within a superconductor in order to realize a fluxonic device is to introduce a periodic potential landscape that causes an easy and a hard direction for vortex motion. In other words, the vortex motion is rectified. By realizing a so-called vortex ratchet with such a potential landscape, vortices may easily be introduced or removed from the superconductor by driving them in the easy or hard directions respectively. We begin by studying the rectification properties of both symmetrically and asymmetrically thickness-modulated superconducting films. These thickness modulations were fabricated with an elegant method of angle-sputter deposition of granular aluminum onto a glass substrate that has a sinusoidal modulation in its thickness. We then explored the rectification of these symmetric and asymmetric films by studying the motion of vortices using cryogenic transport measurements. In these measurements, vortices are driven in both directions across a modulated 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, that is, that there is an overall rectification in their motion. While these measurements performed with the symmetric washboard film seemed to exhibit reversibility in the transport properties, the asymmetric washboard exhibited a mild asymmetry that was much smaller than expected. This result… Advisors/Committee Members: Field, Stuart B. (advisor), Gelfand, Martin (committee member), Buchanan, Kristen (committee member), Neilson, James R. (committee member).

Subjects/Keywords: granular aluminum; superconductivity; phase slip; Abrikosov vortex

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Maughan, Weston F., I. (2020). Vortex rectification and phase slips in superconducting granular aluminum. (Doctoral Dissertation). Colorado State University. Retrieved from http://hdl.handle.net/10217/219605

Chicago Manual of Style (16th Edition):

Maughan, Weston F., II. “Vortex rectification and phase slips in superconducting granular aluminum.” 2020. Doctoral Dissertation, Colorado State University. Accessed April 13, 2021. http://hdl.handle.net/10217/219605.

MLA Handbook (7th Edition):

Maughan, Weston F., II. “Vortex rectification and phase slips in superconducting granular aluminum.” 2020. Web. 13 Apr 2021.

Vancouver:

Maughan, Weston F. I. Vortex rectification and phase slips in superconducting granular aluminum. [Internet] [Doctoral dissertation]. Colorado State University; 2020. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10217/219605.

Council of Science Editors:

Maughan, Weston F. I. Vortex rectification and phase slips in superconducting granular aluminum. [Doctoral Dissertation]. Colorado State University; 2020. Available from: http://hdl.handle.net/10217/219605


Colorado State University

2. Sweeney, Mark Charles. Vortex phases in type-I superconductors.

Degree: PhD, Physics, 2010, Colorado State University

Sufficiently thin films of type-I superconductor in a perpendicular magnetic field exhibit a triangular vortex lattice, while thick films develop an intermediate state. To elucidate what happens between these two regimes, precise numerical calculations have been made within Ginzburg-Landau theory at κ=0.5 and 0.25 for a variety of vortex lattice structures with one flux quantum per unit cell. The phase diagram in the space of mean induction and film thickness includes a narrow wedge in which a square lattice is stable, surrounded by the domain of stability of the triangular lattice at thinner films/lower fields and, on the other side, rectangular lattices with continuously varying aspect ratio. The vortex lattice has an anomalously small shear modulus within and close to the square lattice phase. Solutions of the Ginzburg-Landau equations have also been obtained for bulk systems and thin films for vortex lattices with one vortex but two flux quanta per square or triangular unit cell. These lattices of double fluxoid vortices are thermodynamically unstable in bulk in both type-I and type-II superconductors, as expected. In type-I films the situation is less clear, because the corresponding calculations for more complicated vortex lattice structures are not yet possible. Advisors/Committee Members: Gelfand, Martin Paul (advisor), Mueller, Jennifer L. (committee member), Bradley, Richard M. (committee member), Field, Stuart B. (committee member).

Subjects/Keywords: superconductors; Vortex-motion; Thin films; Superconductivity; Superconductors  – Magnetic fields

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Sweeney, M. C. (2010). Vortex phases in type-I superconductors. (Doctoral Dissertation). Colorado State University. Retrieved from http://hdl.handle.net/10217/44985

Chicago Manual of Style (16th Edition):

Sweeney, Mark Charles. “Vortex phases in type-I superconductors.” 2010. Doctoral Dissertation, Colorado State University. Accessed April 13, 2021. http://hdl.handle.net/10217/44985.

MLA Handbook (7th Edition):

Sweeney, Mark Charles. “Vortex phases in type-I superconductors.” 2010. Web. 13 Apr 2021.

Vancouver:

Sweeney MC. Vortex phases in type-I superconductors. [Internet] [Doctoral dissertation]. Colorado State University; 2010. [cited 2021 Apr 13]. Available from: http://hdl.handle.net/10217/44985.

Council of Science Editors:

Sweeney MC. Vortex phases in type-I superconductors. [Doctoral Dissertation]. Colorado State University; 2010. Available from: http://hdl.handle.net/10217/44985

.