Physics Commons^™

Computational Modeling Of Superconductivity From The Set Of Time-Dependent Ginzburg-Landau Equations For Advancements In Theory And Applications, Iris Mowgood

Computational and Data Sciences (PhD) Dissertations

A full review of the research conducted and published during my PhD studies in Computational and Data Sciences at Chapman University, under the advisement of Dr. Armen Gulian, are presented. Using the set of time-dependent Ginzburg-Landau (TDGL) equations with inclusion of the interference current and the non-equilibrium phonon term, we modeled the dynamics of superconductors in various theory revealing states and practical purposes. A review of the history and phenomenon of superconductivity, including modern applications, is introduced. The Josephson effect and associated Josephson junction are discussed for comparison to our analogous results with the 1-D superconducting wire. The mathematics of …

Stoichiometric Determination Of Hydride Materials At Extreme Conditions, Gregory Alexander Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Hydrogen was predicted to be a high-temperature superconductor at near-megabar conditions in 1968,[1] but only recently was been experimentally observed.[2] This is due to the extraneous metrological constraint of requiring 5 megabars of pressure to stabilize. A more practical approach for synthesis of high-temperature superconductors has been pro-posed through the use of hydride compounds. Recently, a surge of rare earth hydrides have achieved critical superconducting transition temperatures (T_C ) close to room temperature.[3, 4, 5, 6] However, due to limitations of the necessary instrumentation to achieve megabar pressures, many techniques traditionally used to measure stoichiometry are unavailable.Three works presented in …

Nb3Sn Coating Of Twin Axis Cavity And Other Complex Srf Cavity Structures, Jayendrika Kumari Tiskumara

Physics Theses & Dissertations

In the field of Accelerator Science, for the low cost and increased quality factor, thin films coated niobium cavities are used in the modern SRF research. Within the potential substances, Nb₃Sn has shown higher critical temperature than niobium. Here the tin vapor diffusion method is used as the preferred technique to coat niobium cavities. So far, only elliptical cavities have been coated with Nb₃Sn and this technique has not yet been applied to cavities with complex geometries, which are also helpful in the accelerator science field. The Half-wave resonator could provide us data across frequencies of …

High-Frequency Diode Effect In Superconducting Nb3Sn Microbridges, Sara Chahid, Serafim Teknowijoyo, Iris Mowgood, Armen Gulian

Mathematics, Physics, and Computer Science Faculty Articles and Research

The superconducting diode effect has recently been reported in a variety of systems and different symmetry-breaking mechanisms have been examined. However, the frequency range of these potentially important devices still remains obscure. We investigated superconducting microbridges of Nb3Sn in out-of-plane magnetic fields; optimum magnetic fields of ∼10 mT generate ∼10% diode efficiency, while higher fields of ∼15–20 mT quench the effect. The diode changes its polarity with magnetic field reversal. We documented superconductive diode rectification at frequencies up to 100 kHz, the highest reported as of today. Interestingly, the bridge resistance during diode operation reaches a value that is a …

Thin Film Deposition Of Mop, A Topological Semimetal, Robert Browning, Paul Plachinda, Raj Solanki

Physics Faculty Publications and Presentations

MoP is a topological semimetal which has drawn attention due to its unique electrical and optical properties resulting from massless electrons. In order to utilize these properties for practical applications, it is necessary to develop a technique to produce high-quality, large-scale thin films of this 2D material. We report below our initial results of growth of MoP thin films using atomic layer deposition (ALD), where the film grows layer-by-layer. These films were grown on 5 cm × 5 cm silicon oxide coated Si wafers. Resistivity versus temperature measurements show that these films are metallic and includes a partial superconducting phase. …

Pressure - Temperature Phase Diagram Of Crsite3, J L. Musfeldt, David Mandrus, Zhenxian Liu

Chemistry Publications and Other Works

van der Waals solids are well known to host remarkable phase diagrams with competing phases, unusual energy transfer processes, and elusive states of matter. Among this class of materials, chalcogenides have emerged as the most flexible and relevant platforms for unraveling charge-structure-function relationships. In order to explore the properties of complex chalcogenides under external stimuli, we measured the far infrared spectroscopic response of CrSiTe3 under extreme pressure-temperature conditions. Analysis of the 368 cm−1 Si-Te stretching mode and the manner in which it is screened by the closure of the indirect gap reveals that the insulator-metal transition takes place immediately after …

Characterization Of Dissipative Regions Of A N-Doped Superconducting Radio-Frequency Cavity, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Lavarone

Physics Faculty Publications

We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance.Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair …

Development Of A Prototype Superconducting Radio-Frequency Cavity For Conduction Cooled Accelerators, Gianluigi Ciovati, J. Anderson, S. Balachandran, G. Cheng, B. Coritron, E. Daly, P. Dhakal, Alex Gurevich, F. Hannon, K. Harding, L. Holland, F. Marhauser, K. Mclaughlin, D. Packard, T. Powers, U. Pudasaini, J. Rathke, R. Rimmer, T. Schultheiss, H. Vennekate, D. Vollmer

Physics Faculty Publications

The higher efficiency of superconducting radio-frequency (SRF) cavities compared to normal -conducting ones enables the development of high-energy continuous-wave linear accelerators (linacs). Recent progress in the development of high-quality Nb₃Sn film coatings along with the availability of cryocoolers with high cooling capacity at 4 K makes it feasible to operate SRF cavities cooled by thermal conduction at relevant accelerating gradients for use in accelerators. A possible use of conduction-cooled SRF linacs is for environmental applications, requiring electron beams with energy of 1-10 MeV and 1 MW of power. We have designed a 915 MHz SRF linac for such …

Direct Current Magnetic Hall Probe Technique For Measurement Of Field Penetration In Thin Film Superconductors For Superconducting Radio Frequency Resonators, Iresha Harshani Senevirathne, Alex Gurevich, Jean Delayen

Physics Faculty Publications

Superconducting Radio Frequency (SRF) cavities used in particle accelerators are typically formed from or coated with superconducting materials. Currently, high purity niobium is the material of choice for SRF cavities that have been optimized to operate near their theoretical field limits. This brings about the need for significant R & D efforts to develop next generation superconducting materials that could outperform Nb and keep up with the demands of new accelerator facilities. To achieve high quality factors and accelerating gradients, the cavity material should be able to remain in the superconducting Meissner state under a high RF magnetic field without …

Lower Temperature Annealing Of Vapor Diffused Nb3Sn For Accelerator Cavities, Jayendrika K. Tiskumara, Jean R. Delayen, G. V. Eremeev, U. Pudasaini

Physics Faculty Publications

Nb₃Sn is a next-generation superconducting material for the accelerator cavities with higher critical temperature and superheating field, both twice compared to Nb. It promises superior performance and higher operating temperature than Nb, resulting in significant cost reduction. So far, the Sn vapor diffusion method is the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Although several post-coating techniques (chemical, electrochemical, mechanical) have been explored to improve the surface quality of the coated surface, an effective process has yet to be found. Since there are only a few studies on the post-coating heat treatment …

Developing Effective Theories: A Case Study In Monolayer Iron Selenide, Joseph O'Halloran

Theses and Dissertations

In this work, we outline the development of a series of models which have allowed us to investigate the low-temperature phases of monolayer FeSe. These models are built using group theoretic arguments to ensure the constraints provided by the crystal symmetry are satisfied. We investigate the interplay between stripe antiferromagnetism and spin-vortex crystal order in the framework of the Landau theory of phase transitions. By considering inversion symmetry breaking terms in the Landau free-energy, we show that the spin-vortex crystal is preferred when the non-symmorphic parent symmetry group $P4/nmm$ is reduced to a symmorphic subgroup.

We also consider symmetry constraints …

Numerical Calculation Of Losses Of Trapped Vortices Under Strong Rf Meissner Current And Dc Superheating Field In Type Ii Superconductors, Walive Pathiranage Manula Randhika Pathirana

Physics Theses & Dissertations

Research on the vortex dynamics and enhancing of superheating field in superconductors has attracted much attention in accelerator physics community to develop next-generation high-performance accelerator cavities. However, the extreme dynamics of curvilinear elastic vortices driven by very strong currents close to the depairing limit or superheating field of a superconductor with a nanostructured surface has not been well understood. We calculated the superheating field H_sh and critical momentum kc characterizing the wavelength of the instability λ_m of the Meissner state to flux penetration by solving numerically the Ginzburg-Landau equations. A bulk superconductor, superconductor with the inhomogeneous surface disorder …

Novel Low Temperature Properties Of Filled And Unfilled Single Crystal Irsb3, Matthew Cook

Dissertations

The skutterudite family of materials has garnered a lot of attention in the condensed matter community and it persists to be an important system for exploring the fundamental physics of solids. The initial interest into compounds with this common structure was due to their promising thermoelectric properties giving the possibility of efficient energy harvesting. Since, there has been a huge effort to systematically synthesize new filled skutterudite compounds, as nearly every type of strongly correlated behavior has been found within this family. As the field of topological materials has gained momentum, these materials have also been given a renewed interest …

Numerical Studies Of Superconductivity And Charge-Density-Waves: Progress On The 2d Holstein Model And A Superconductor-Metal Bilayer, Philip M. Dee

Doctoral Dissertations

The problem of superconductivity has been central in many areas of condensed matter physics for over 100 years. Despite this long history, there is still no theory capable of describing both conventional and unconventional superconductors. Recent experimental observations such as the dilute superconductivity in SrTiO₃ and near room-temperature superconductivity in hydride compounds under extreme pressure have renewed interest in electron-phonon systems. Adding to this is evidence that electron-phonon coupling may play a supporting role in unconventional systems like the cuprates and monolayer FeSe on SrTiO₃.

One way to make sense of these observations is to construct simple …

Nb3Sn Coating Of Complex Srf Cavity Structures, Jayendrika Tiskumara, Uttar Pudasaini, Grigory Eremeev, Charlie Reece, Jean Delayen

College of Sciences Posters

In the modern SRF research, Thin films coated niobium cavities are used for the low cost and increased quality factor. Among the potential thin film materials applied on the niobium, performances demonstrated by the Nb3Sn cavities makes this material attractive for SRF accelerator applications giving higher critical temperature and higher accelerating gradients. While the majority of research efforts are currently focused on the development of elliptical single-cell and multi-cell cavities, the potential of this material is evident to other cavity types, which may have complex geometries. We are working towards the development of Nb₃Sn-coated Half-wave resonator and twin …

The Magnetic Field Penetration Measurement Of Thin Film And Multilayered Superconductors For Srf Cavities, Iresha Harshani Senevirathne, Jean Delayen

College of Sciences Posters

Radio Frequency (RF) Cavities are used in particle accelerators and they are typically formed from or coated with superconducting materials. High purity niobium is the material of choice for SRF cavities and niobium cavities operate at their theoretical field limits. SRF researchers have begun a significant R&D effort to develop alternative materials to continue to keep up with the demands of new accelerator facilities. To achieve high performance with high accelerating gradient, cavity material should have an ability to persist in superconducting state under high magnetic field without magnetic flux penetration through the cavity wall. Therefore, the magnetic field at …

Majorana Quasiparticles In Topological Material Interfaces, David Alspaugh

LSU Doctoral Dissertations

In this dissertation we analyze how Majorana quasiparticles found on material interfaces of both topological insulators (TIs) and topological superconductors (TSCs) are affected by imperfections within their local environment. While these quasiparticles are predicted to be critical for the construction of quantum computers, they are typically modeled only under pristine conditions. Thus, although quantum computers may require the spatial manipulation of Majorana quasiparticles, these topological material interfaces are commonly studied in static contexts and their response to manipulation remains an open question. We first demonstrate that interface potentials on the topological insulator Bi₂Se₃ can enable the emergence …

Experimental Exploration Of Shared Magnetic Phases Between Diverse Systems Of Iron-Pnictide Superconductors, Ryan Scott Stadel

Graduate Research Theses & Dissertations

The exciting field of iron-pnictide superconductors offers unique opportunities for studying the relationship between magnetism and unconventional superconductivity. This is vital to developing an understanding of the microscopic origin of high-temperature superconductivity, which is itself an important step in harnessing such a potentially revolutionary technology.

Polycrystalline and crystalline samples are synthesized over a diverse collection of related iron-pnictide systems including (Ca,Sr,Ba)1-xNaxFe2As2, Ba(Fe1-xCox)2As2 (122s), and LaFeAs1-xPxO, and TbFeAs1-xPxO (1111s). These compounds are characterized through various types of neutron and x-ray diffraction on multiple instruments, as well as muon spin resonance, and magnetic susceptibility measurements.

A thorough investigation into the conditions under …

Magnetic Field Sensors For Detection Of Trapped Flux In Superconducting Radio Frequency Cavities, Ishwari Prasad Parajuli, Gianluigi Ciovati, Jean R. Delayen

Physics Faculty Publications

Superconducting radio frequency (SRF) cavities are fundamental building blocks of modern particle accelerators. They operate at liquid helium temperatures (2–4 K) to achieve very high quality factors (10¹⁰–10¹¹). Trapping of magnetic flux within the superconductor is a significant contribution to the residual RF losses, which limit the achievable quality factor. Suitable diagnostic tools are in high demand to understand the mechanisms of flux trapping in technical superconductors, and the fundamental components of such diagnostic tools are magnetic field sensors. We have studied the performance of commercially available Hall probes, anisotropic magnetoresistive sensors, and flux-gate magnetometers with …

Nb3Sn Coating Of Twin Axis Cavity For Srf Applications, J. K. Tiskumara, Jean R. Delayen, G. V. Eremeev, U. Pudasaini, C. E. Reece

Physics Faculty Publications

The twin axis cavity with two identical accelerating beams has been proposed for energy recovery linac (ERL) applications. Nb₃Sn is a superconducting material with a higher critical temperature and a higher critical field as compared to Nb, which promises a lower operating cost due to higher quality factors. Two niobium twin axis cavities were fabricated at JLab and were proposed to be coated with Nb₃Sn. Due to their more complex geometry, the typical coating process used for basic elliptical cavi-ties needs to be improved to coat these cavities. This development advances the current coating system at …

Exploring Structural And Electronic Properties Of Triangular Adatom Layers On The Silicon Surface Through Adsorbate Doping, Tyler S. Smith

Doctoral Dissertations

The analysis of the electronic structure and morphology of 1/3 monolayers (ML) of Sn or Pb on Si(111) and Ge(111) has played an important role in understanding the role of electronic correlations in two dimensions. Specifically, the two-dimensional lattice of partially filled dangling bonds of these so-called α-phases has been an important testbed for studying structural phase transitions and correlated electronic phenomena ever since the discovery of a surface charge density wave in the Pb/Ge(111) system more than two decades ago. With the exception of the novel Sn/Si(111) system, all $\alpha$-phases undergo a charge ordering transition at low temperature. The …

Magnesium Diboride Embedded Multi-Walled Carbon Nanotube Yarns, Ujjal Lamichhane

Theses and Dissertations

The discovery of superconductivity in a simple hexagonal binary compound of MgB2 at a relatively high critical temperature ~39 K renewed the interest in the field of superconductivity. Twisted laminar superconducting composite structures based on coiled multi-walled carbon nanotube (MWCNT) yarns were crafted by integrating magnesium and boron homogeneous mixture into the carbon nanotube sheets. After the ignition of the Mg/B/MWCNT system, under the controlled argon environment and uniform heating rate, the high exothermic reaction between magnesium (Mg) and boron (B) with stoichiometric ratio produced the MgB2/MWCNT superconducting composite yarns. The XRD analysis confirmed that the heated sample consists of …

Superconducting Phase Transition In Inhomogeneous Chains Of Superconducting Islands, Eduard Ilin, Irina Burkova, Xiangyu Song, Michael Pak, Dmitri S. Golubev, Alexey Bezryadin

Faculty Publications

We study one-dimensional chains of superconducting islands with a particular emphasis on the regime in which every second island is switched into its normal state, thus forming a superconductor-insulator-normal metal (S-I-N) repetition pattern. As is known since Giaever tunneling experiments, tunneling charge transport between a superconductor and a normal metal becomes exponentially suppressed, and zero-bias resistance diverges, as the temperature is reduced and the energy gap of the superconductor grows larger than the thermal energy. Here we demonstrate that this physical phenomenon strongly impacts transport properties of inhomogeneous superconductors made of weakly coupled islands with fluctuating values of the critical …

Superconductivity In La₂Ni₂In, Jannis Maiwald, Igor I. Mazin, Alex Gurevich, Meigan Aronson

Physics Faculty Publications

We report here the properties of single crystals of La₂Ni₂In. Electrical resistivity and specific heat measurements concur with the results of density functional theory calculations, finding that La₂Ni₂In is a weakly correlated metal, where the Ni magnetism is almost completely quenched, leaving only a weak Stoner enhancement of the density of states. Superconductivity is observed at temperatures below 0.9 K. A detailed analysis of the field and temperature dependencies of the resistivity, magnetic susceptibility, and specific heat at the lowest temperatures reveals that La₂Ni₂In is a dirty type-II …

The Synthesis Of Pb2sr2sm1-Xcaxcu3o8 And Characterization Of Its Structural And Superconducting Properties., Deblina Das

Graduate Research Theses & Dissertations

Superconducting lead-based cuprate materials of the 2213 structural type, Pb2Sr2MCu3O8 (M=Sm1-xCax, Y1-xCax, Er1-xCax and Yb1-xCax), were synthesized and characterized using x-ray powder diffraction and the Rietveld structural refinements method. Pb2Sr2Sm1-xCaxCu3O8 single crystals were grown by an optimized flux method using various combinations of PbO/PbF2 solvents. Samples with different Sm/Ca ratios were investigated for their superconducting properties. Magnetic measurements reveal the presence of a transition at 120K. Preliminary x-ray diffuse scattering experiment at the Advanced Photon Source of Argonne National Laboratory demonstrates the high quality of one of our crystals and the presence of rod-like diffuse scattering connecting the Bragg peaks …

Observation Of In-Plane Magnetic Field Induced Phase Transitions In Fese, Jong Mok Ok, Chang Il Kwon, Yoshimitsu Kohama, Jung Sang You, Sun Kyu Park, Ji-Hye Kim, Y.J. Jo, E.S. Choi, Koichi Kindo, Woun Kang, Ki-Seok Kim, E. G. Moon, Alex Gurevich, Jun Sung Kim

Physics Faculty Publications

We investigate thermodynamic properties of FeSe under in-plane magnetic fields using torque magnetometry, specific heat, and magnetocaloric measurements. Below the upper critical field H_c2, we observed the field induced anomalies at H₁ ∼ 15 T and H₂ ∼ 22 T near H ∥ ab and below a characteristic temperature T* ∼ 2 K. The transition magnetic fields H₁ and H₂ exhibit negligible dependence on both temperature and field orientation. This contrasts to the strong temperature and angle dependence of H_c2, suggesting that these anomalies are attributed to the field induced phase transitions, …

Dynamic Pair-Breaking Current, Critical Superfluid Velocity, And Nonlinear Electromagnetic Response Of Nonequilibrium Superconductors, Ahmad Sheikhzada, Alex Gurevich

Physics Faculty Publications

We report numerical calculations of a dynamic pair-breaking current density J_d and a critical superfluid velocity v_d in a nonequilibrium superconductor carrying a uniform, large-amplitude AC current density J(t)=J_asinΩt with Ω well below the gap frequency Ω ≪ Δ₀/h. The dependencies J_d(Ω,T) and v_d(Ω,T) near the critical temperature T_cwere calculated from either the full time-dependent nonequilibrium equations for a dirty s-wave superconductor or the time-dependent Ginzburg-Landau (TDGL) equations for a gapped superconductor, taking into account the GL relaxation time of the order parameter GL …

Heisenberg Model Analysis On Inelastic Powder Neutron Scattering Data Using Parent And K Doped Bamn2as2 Samples, Mehmet Ramazanoglu, Aashish Sapkota, Abhishek Pandey, Jagat Lamsal, Douglas L. Abernathy, Jennifer L. Niedziela, Matthew B. Stone, R. Salci, D. A. Acar, F. O. Oztirpan, Şener Ozonder, Andreas Kreyssig, Alan I. Goldman, David C. Johnston, Robert J. Mcqueeney

A. I. Goldman

Low temperature powder inelastic neutron scattering measurements were performed on three different powder samples; parent BaMn2As2,12.5% K-doped Ba0.875K0.125Mn2As2 and 25% K-doped Ba(0.75)K0.25Mn2As2. The Heisenberg Model involving J1‐J2‐Jz coupling constants were compared to the data by a powder integration routine using Monte Carlo integration methods. The best magnetic parameters were selected using a chi-square test where model intensities were compared to the full (q,E) dependence of magnetic scattering. A key step to this analysis is the characterization of the background which is formed mostly by phonon scattering intensities along with other sources including the magnetic impurity scattering events. The calculated powder …

Loop Currents And Anomalous Hall Effect From Time-Reversal Symmetry-Breaking Superconductivity On The Honeycomb Lattice, P.M.R. Brydon, D.S.L. Abergel, Daniel Agterberg, Victor M. Yakovenko

Physics Faculty Articles

We study a tight-binding model on the honeycomb lattice of chiral d-wave superconductivity that breaks time-reversal symmetry. Because of its nontrivial sublattice structure, we show that it is possible to construct a gauge-invariant time-reversal-odd bilinear of the pairing potential. The existence of this bilinear reflects the sublattice polarization of the pairing state. We show that it generates persistent loop current correlations around each lattice site and opens a topological mass gap at the Dirac points, resembling Haldane’s model of the anomalous quantum Hall effect. In addition to the usual chiral d-wave edge states, there also exist electronlike edge …

Ternary Inorganic Electrides With Mixed Bonding, Junjie Wang, Qiang Zhu, Zhenhai Wang, Hideo Hosono

Physics & Astronomy Faculty Research

A high-throughput screening based on first-principles calculations was performed to search for new ternary inorganic electrides. From the available materials database, we identified three new thermodynamically stable materials (Li12Mg3Si4, NaBa2O, and Ca5Ga2N4) as potential electrides made by main group elements, in addition to the well known mayenite based electride (C12A7:e−). Different from those conventional inorganic electrides in which the excess electrons play only the role of anions, the three new materials, resembling the electrides found in simple metals under high pressure, possess mixed ionic and metallic bonding. The interplay between two competing mechanisms, together with the different crystal packing motifs, …