A5070874414- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Particle accelerators and beam dynamics
- Photochemistry and Electron Transfer Studies
- Superconductivity in MgB2 and Alloys
- Quantum, superfluid, helium dynamics
- Surface and Thin Film Phenomena
- Topological Materials and Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Iron-based superconductors research
- Electrochemical Analysis and Applications
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Spectroscopy and Quantum Chemical Studies
- Electron Spin Resonance Studies
- Lanthanide and Transition Metal Complexes
- DNA and Nucleic Acid Chemistry
- Rare-earth and actinide compounds
- Magnetic properties of thin films
- Plasmonic and Surface Plasmon Research
- Photoreceptor and optogenetics research
- Advanced biosensing and bioanalysis techniques
- Graphene research and applications
- Molecular Junctions and Nanostructures
- Electrowetting and Microfluidic Technologies
Louisiana State University
2022-2025
Institute of Theoretical Physics
2023
Northwestern University
2014-2023
Fermi National Accelerator Laboratory
2022
We report results for the superconducting transition temperature and anisotropic energy gap pure niobium based on Eliashberg’s equations electron phonon band structures computed from density functional theory. The electronic structure is used to construct Fermi surface calculate velocity at each point surface. bands are in excellent agreement with inelastic neutron scattering data. corresponding of states electron–phonon coupling define spectral function, α 2 F ( p , ′; ω ), pairing...
Niobium is one of the most researched superconductors, both theoretically and experimentally. It enormously significant in all branches superconducting applications, from powerful magnets to quantum computing. therefore imperative understand its fundamental properties great detail. Here, we use results recent microscopic calculations anisotropic electronic, phonon, properties, apply a thermodynamic criterion for type superconductivity, more accurate straightforward than conventional...
Abstract Niobium superconducting radio-frequency (SRF) cavities for high energy accelerator applications have been greatly improved in terms of the quality factor Q by techniques such as Nitrogen doping. However, mechanisms leading improvement are still not fully understood. Quite recently SRF group at Fermilab measured anomalies frequency shift N-doped near transition temperature. Here we report our theoretical analysis these results based on microscopic theory superconductivity that...
When a molecular electron donor interacts with multiple acceptors, quantum coherence can enhance the transfer (ET) rate. Here we report photodriven ET rates in pair of donor–acceptor (D-A) compounds that link one anthracene (An) to or two equivalent 1,4-benzoquinone (BQ) acceptors. Subpicosecond from lowest excited singlet state An BQs is about 2.4 times faster than BQ at room temperature, but 5 cryogenic temperatures. This factor 2 increase results transition acceptors temperature...
Niobium is one of the most studied superconductors, both theoretically and experimentally. It tremendously important for applications, it has highest superconducting transition temperature, ${T}_{c}=9.32$ K, all pure metals. In addition to power applications in alloys, niobium used sensitive magnetosensing, radio-frequency cavities, and, more recently, as circuit metallization layers qubits. A detailed understanding its electronic structure, especially normal state anisotropies, crucial...
In a three-site representation, we study spin polarization transfer from radical pair spins to nearby electron or nuclear spin. The quantum dynamics of the is governed by constant exchange interaction between which have different Zeeman frequencies. Radical can recombine singlet ground state lower energy triplet states. It then shown that coherent induces on third in presence magnetic field. depends difference frequencies, and recombination rates, dipole-dipole interactions spins....
Subnanosecond radical pair (RP) formation by electron transfer from an excited singlet state or bond breaking produces two correlated spins coupled their spin–spin exchange (J) and magnetic dipole (D) interactions. In the high field limit, two-spin system can be described a (S) three triplet states (T0, T+1, T–1). When J is small relative to Zeeman interaction, |T0⟩ only that populated coherent spin mixing with |S⟩ because |T+1⟩ |T–1⟩ are well-separated large energy gap. Herein, we describe...
Niobium superconducting radio-frequency (SRF) cavities for high energy accelerator applications have been greatly improved in terms of the quality factor $Q$ by techniques such as Nitrogen doping. However, mechanisms leading improvement are still not fully understood. Quite recently SRF group at Fermilab measured anomalies frequency shift N-doped near transition temperature. Here we report our theoretical analysis these results based on microscopic theory superconductivity that incorporates...
Recently reported anomalies in frequency shift of order δ f ∼ 0.1 -10 kHz for Niobium SRF cavities a narrow temperature region near T c 9 K are sensitive to the surface preparation and Nitrogen doping.We developed methods calculating current response Nb cavities, as well resonant quality factor, functions temperature, disorder based on Keldysh formulation theory nonequilibrium superconductivity coupled with Maxwell's boundary conditions electromagnetic field.We show that anomaly is impurity...
We present the results for resonant frequency shift and quality factor of disordered niobium (Nb) superconducting radio-frequency cavities driven out equilibrium by microwave field. The theory is based on non-equilibrium superconductivity current response to electromagnetic field at vacuum–metal interface. are able accurately predict observed shifts with a precision order fractions kHz over full temperature range 0 < T ≤ c , including negative anomalies that very near . origin these...
The coherent hole transfer in three types of DNA hairpins containing strands with adenine (A) and guanine (G) nucleobases has been studied. investigated involve An+1GGAn, AnGAGAn, or (AG)2nA that connect the donor acceptor located on opposite ends hairpins. positive charge from photo-excited to is shown be slower for An+1GGAn comparison AnGAGAn sequences. We have revealed this due reflectional symmetry last two sequences respect axis passing through middle base. As demonstrated, sequence...
We study electron transfer (ET) in a two level quantum system coupled to glassy viscous bath. The bath is modeled by the Cole-Davidson (CD) spectral density. ET this model compared normal Drude-Debye (DD) model. It shown that at low temperatures and when coupling weak, preserves coherence for longer time. However strong regime, tunneling rate higher CD. In classical high temperature limit difference between CD DD models negligible.
We report results for the superconducting transition temperature and anisotropic energy gap pure Niobium based on Eliashberg's equations electron phonon band structures computed from density functional theory. The electronic structure is used to construct Fermi surface calculate velocity at each point surface.The bands are in excellent agreement with inelastic neutron scattering data. corresponding of states electron-phonon coupling define spectral function, $\alpha^2F({\bf p},{\bf...
Niobium is commonly used for superconducting quantum systems as readout resonators, capacitors, and interconnects. The coherence time of the qubits mainly limited by microwave dissipation attributed to two-level system defects at interfaces, such Nb/Si Nb/air interface. One way improve interface quality thermal annealing, shown extensive studies in 3D radio frequency (SRF) cavities. However, it unclear how microstructure chemistry structures change during heat treatment. To address this...
Niobium is commonly used for superconducting quantum systems as readout resonators, capacitors, and interconnects. But structural defects at the Nb/Si air/Nb interface may be a major source of two-level system (TLS), which are detrimental to device's coherence time. Thus, identifying understanding microscopic origin possible TLS in Nb-based devices their relationship processing key qubit performance improvement. This work studied structure thermal stability Nb films deposited on Si wafers by...
Recently reported anomalies in frequency shift of order $\delta f\sim 0.1 -10\,\mbox{kHz}$ for Niobium SRF cavities a narrow temperature region near $T_c\simeq 9\,\mbox{K}$ are sensitive to the surface preparation and Nitrogen doping. We developed methods calculating current response Nb cavities, as well resonant quality factor, functions temperature, disorder based on Keldysh formulation theory nonequilibrium superconductivity coupled with Maxwell's boundary conditions electromagnetic...
We present results for the resonant frequency shift and quality factor of disordered Nb SRF cavities driven out equilibrium by microwave field. The theory is based on nonequilibrium superconductivity current response to electromagnetic field at vacuum-metal interface. are able accurately predict observed shifts with a precision order several Hz over full temperature range $0 < T \le T_c$, including negative anomalies that very near $T_c$. origin these shown be competition between normal...
Niobium is one of the most researched superconductors, both theoretically and experimentally. It enormously significant in all branches superconducting applications, from powerful magnets to quantum computing. is, therefore, imperative understand its fundamental properties great detail. Here we use results recent microscopic calculations anisotropic electronic, phonon, properties, apply thermodynamic criterion for type superconductivity, more accurate straightforward than a conventional...
Niobium is one of the most studied superconductors, both theoretically and experimentally. It tremendously important for applications, it has highest superconducting transition temperature, $T_{c}=9.33$ K, all pure metals. In addition to power applications in alloys, niobium used sensitive magneto-sensing, radio-frequency cavities, and, more recently, as circuit metallization layers qubits. A detailed understanding its electronic structure, especially normal state anisotropies, crucial...