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Articles 1  30 of 52
FullText Articles in Physics
Loop Currents And Anomalous Hall Effect From TimeReversal SymmetryBreaking Superconductivity On The Honeycomb Lattice, P.M.R. Brydon, D.S.L. Abergel, Daniel Agterberg, Victor M. Yakovenko
Loop Currents And Anomalous Hall Effect From TimeReversal SymmetryBreaking Superconductivity On The Honeycomb Lattice, P.M.R. Brydon, D.S.L. Abergel, Daniel Agterberg, Victor M. Yakovenko
Physics Faculty Articles
We study a tightbinding model on the honeycomb lattice of chiral dwave superconductivity that breaks timereversal symmetry. Because of its nontrivial sublattice structure, we show that it is possible to construct a gaugeinvariant timereversalodd 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 dwave edge states, there also exist electronlike ...
Ternary Inorganic Electrides With Mixed Bonding, Junjie Wang, Qiang Zhu, Zhenhai Wang, Hideo Hosono
Ternary Inorganic Electrides With Mixed Bonding, Junjie Wang, Qiang Zhu, Zhenhai Wang, Hideo Hosono
Physics & Astronomy Faculty Publications
A highthroughput screening based on firstprinciples 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 ...
Scanning Tunneling Spectroscopy Investigations Of SuperconductingDoped Topological Insulators: Experimental Pitfalls And Results, Stefan Wilfert, Paolo Sessi, Zhiwei Wang, Henrik Schmidt, M. Carmen MartínezVelarte, Seng Huat Lee, Yew San Hor, Alexander F. Otte, Yoichi Ando, Weida Wu, Matthias Bode
Scanning Tunneling Spectroscopy Investigations Of SuperconductingDoped Topological Insulators: Experimental Pitfalls And Results, Stefan Wilfert, Paolo Sessi, Zhiwei Wang, Henrik Schmidt, M. Carmen MartínezVelarte, Seng Huat Lee, Yew San Hor, Alexander F. Otte, Yoichi Ando, Weida Wu, Matthias Bode
Physics Faculty Research & Creative Works
Recently, the doping of topological insulators has attracted significant interest as a potential route towards topological superconductivity. Because many experimental techniques lack sufficient surface sensitivity, however, definite proof of the coexistence of topological surface states and surface superconductivity is still outstanding. Here we report on highly surface sensitive scanning tunneling microscopy and spectroscopy experiments performed on Tldoped Bi_{2}Te_{3}, a threedimensional topological insulator which becomes superconducting in the bulk at T_{C}=2.3 K. Landau level spectroscopy as well as quasiparticle interference mapping clearly demonstrated the presence of a topological surface state with a Dirac point energy ...
Universal Doping Evolution Of The Superconducting Gap Anisotropy In Single Crystals Of ElectronDoped Ba(Fe1Xrhx)(2)As2 From London Penetration Depth Measurements, Hyunsoo Kim, Makariy A. Tanatar, C. Martin, E. C. Blomberg, Ni Ni, Sergey L. Bud’Ko, Paul C. Canfield, Ruslan Prozorov
Universal Doping Evolution Of The Superconducting Gap Anisotropy In Single Crystals Of ElectronDoped Ba(Fe1Xrhx)(2)As2 From London Penetration Depth Measurements, Hyunsoo Kim, Makariy A. Tanatar, C. Martin, E. C. Blomberg, Ni Ni, Sergey L. Bud’Ko, Paul C. Canfield, Ruslan Prozorov
Ames Laboratory Accepted Manuscripts
Doping evolution of the superconducting gap anisotropy was studied in single crystals of 4delectron doped Ba(Fe1xRhx)(2)As2 using tunnel diode resonator measurements of the temperature variation of the London penetration depth Delta lambda(T). Single crystals with doping levels representative of an underdoped regime x = 0.039 (Tc = 15.5 K), close to optimal doping x = 0.057 (Tc = 24.4 K) and overdoped x = 0.079 (Tc = 21.5 K) and x = 0.131 (Tc = 4.9 K) were studied. Superconducting energy gap anisotropy was characterized by the exponent, n, by fitting the data to the powerlaw ...
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
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
Ames Laboratory Accepted Manuscripts
Low temperature powder inelastic neutron scattering measurements were performed on three different powder samples; parent BaMn2As2,12.5% Kdoped Ba0.875K0.125Mn2As2 and 25% Kdoped 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 chisquare 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 ...
Pressure Induced HalfCollapsedTetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. Mcqueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield
Pressure Induced HalfCollapsedTetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. Mcqueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield
Ames Laboratory Accepted Manuscripts
We report the temperaturepressure phase diagram of CaKFe4As4 established using highpressure electrical resistivity, magnetization, and highenergy xray diffraction measurements up to 6 GPa. With increasing pressure, both resistivity and magnetization data show that the bulk superconducting transition of CaKFe4As4 is suppressed and then disappears at p≳4 GPa. Highpressure xray data clearly indicate a phase transition to a collapsed tetragonal phase in CaKFe4As4 under pressure that coincides with the abrupt loss of bulk superconductivity near 4 GPa. The xray data, combined with resistivity data, indicate that the collapsed tetragonal transition line is essentially independent of pressure, occurring at 4.0 ...
Effective OneDimensional Coupling In The Highly Frustrated SquareLattice Itinerant Magnet Caco 2 − Y As 2, Aashish Sapkota, B. G. Ueland, V. K. Anand, N. S. Sangeetha, D. L. Abernathy, M. B. Stone, J. L. Niedziela, D. C. Johnston, A. Kreyssig, A. I. Goldman, R. J. Mcqueeney
Effective OneDimensional Coupling In The Highly Frustrated SquareLattice Itinerant Magnet Caco 2 − Y As 2, Aashish Sapkota, B. G. Ueland, V. K. Anand, N. S. Sangeetha, D. L. Abernathy, M. B. Stone, J. L. Niedziela, D. C. Johnston, A. Kreyssig, A. I. Goldman, R. J. Mcqueeney
Ames Laboratory Accepted Manuscripts
Inelastic neutron scattering measurements on the itinerant antiferromagnet CaCo2−yAs2 at a temperature of 8 K reveal two orthogonal planes of scattering perpendicular to the Co square lattice in reciprocal space, demonstrating the presence of effective onedimensional spin interactions. These results are shown to arise from nearperfect bond frustration within the J1J2 Heisenberg model on a square lattice with ferromagnetic J1 and hence indicate that the extensive previous experimental and theoretical study of the J1J2 Heisenberg model on localmoment square spin lattices should be expanded to include itinerant spin systems.
Calorimetric Measurements Of MagneticFieldInduced Inhomogeneous Superconductivity Above The Paramagnetic Limit, Charles C. Agosta, Nathanael Alexander Fortune, Scott T. Hannahs, Shuyao Gu, Lucy Liang, JuHyun Park, John A. Schleuter
Calorimetric Measurements Of MagneticFieldInduced Inhomogeneous Superconductivity Above The Paramagnetic Limit, Charles C. Agosta, Nathanael Alexander Fortune, Scott T. Hannahs, Shuyao Gu, Lucy Liang, JuHyun Park, John A. Schleuter
Physics: Faculty Publications
We report the first magnetocaloric and calorimetric observations of a magneticfieldinduced phase transition within a superconducting state to the longsought exotic FuldeFerrellLarkinOvchinnikov (FFLO) superconducting state, first predicted over 50 years ago. Through the combination of bulk thermodynamic calorimetric and magnetocaloric measurements in the organic superconductor κ−(BEDT−TTF)2Cu(NCS)2 as a function of temperature, magnetic field strength, and magnetic field orientation, we establish for the first time that this fieldinduced firstorder phase transition at the paramagnetic limit Hp is a transition to a higherentropy superconducting phase, uniquely characteristic of the FFLO state. We also establish that this highfield ...
Rotational Symmetry Breaking In A Trigonal Superconductor NbDoped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li
Rotational Symmetry Breaking In A Trigonal Superconductor NbDoped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li
Physics Faculty Research & Creative Works
The search for unconventional superconductivity has been focused on materials with strong spinorbit coupling and unique crystal lattices. Doped bismuth selenide (Bi_{2}Se_{3}) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)doped Bi_{2}Se_{3 ...}
Cryogenic Rf Test Of The First Srf Cavity Etched In An Rf Ar/Cl2 Plasma, J. Upadhyay, A. Palczewski, S. Popovic, A.M. ValenteFeliciano, Do Im, H. L. Phillips, L. Vuskovic
Cryogenic Rf Test Of The First Srf Cavity Etched In An Rf Ar/Cl2 Plasma, J. Upadhyay, A. Palczewski, S. Popovic, A.M. ValenteFeliciano, Do Im, H. L. Phillips, L. Vuskovic
Physics Faculty Publications
An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl_{2} cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity's inner wall was then exposed to the capacitive discharge in a ...
Exact Solution Of Quadratic Fermionic Hamiltonians For Arbitrary Boundary Conditions, Abhijeet Alase, Emilio Cobanera, Gerardo Ortiz, Lorenza Viola
Exact Solution Of Quadratic Fermionic Hamiltonians For Arbitrary Boundary Conditions, Abhijeet Alase, Emilio Cobanera, Gerardo Ortiz, Lorenza Viola
Open Dartmouth: Faculty Open Access Scholarship
We present a procedure for exactly diagonalizing finiterange quadratic fermionic Hamiltonians with arbitrary boundary conditions in one of D dimensions, and periodic in the remaining D−1. The key is a Hamiltoniandependent separation of the bulk from the boundary. By combining information from the two, we identify a matrix function that fully characterizes the solutions, and may be used to construct an efficiently computable indicator of bulkboundary correspondence. As an illustration, we show how our approach correctly describes the zeroenergy Majorana modes of a timereversalinvariant swave twoband superconductor in a Josephson ring configuration, and predicts that a fractional 4πperiodic Josephson ...
Dynamical Generation Of Floquet Majorana Flat Bands In SWave Superconductors, A. Poudel, G. Ortiz, L. Viola
Dynamical Generation Of Floquet Majorana Flat Bands In SWave Superconductors, A. Poudel, G. Ortiz, L. Viola
Open Dartmouth: Faculty Open Access Scholarship
We present quantum control techniques to engineer flat bands of symmetryprotected Majorana edge modes in s wave superconductors. Specifically, we show how periodic control may be employed for designing timeindependent effective Hamiltonians, which support Floquet Majorana flat bands, starting from equilibrium conditions that are either topologically trivial or only support individual Majorana pairs. In the first approach, a suitable modulation of the chemical potential simultaneously induces Majorana flat bands and dynamically activates a preexisting chiral symmetry which is responsible for their protection. In the second approach, the application of effective parity kicks dynamically generates a desired chiral symmetry by suppressing ...
Majorana Flat Bands In S Wave Gapless Topological Superconductors, Shusa Deng, Gerardo Ortiz, Amrit Poudel, Lorenza Viola
Majorana Flat Bands In S Wave Gapless Topological Superconductors, Shusa Deng, Gerardo Ortiz, Amrit Poudel, Lorenza Viola
Open Dartmouth: Faculty Open Access Scholarship
We demonstrate how the nontrivial interplay between spinorbit coupling and nodeless swave superconductivity can drive a fully gapped twoband topological insulator into a timereversal invariant gapless topological superconductor supporting symmetryprotected Majorana flat bands. We characterize topological phase diagrams by a Z2×Z2 partial Berryphase invariant, and show that, despite the trivial crystal geometry, no unique bulkboundary correspondence exists. We trace this behavior to the anisotropic quasiparticle bulk gap closing, linear vs quadratic, and argue that this provides a unifying principle for gapless topological superconductivity. Experimental implications for tunneling conductance measurements are addressed, relevant for lead chalcogenide materials.
Higher Order Mode Damping In Superconducting Spoke Cavities, C. S. Hopper, J. R. Delayen
Higher Order Mode Damping In Superconducting Spoke Cavities, C. S. Hopper, J. R. Delayen
Physics Faculty Publications
Parasitic higher order modes (HOMs) can be severely detrimental to the performance of superconducting cavities. For this reason, the mode spectrum and beam coupling strength must be examined in detail to determine which modes must be damped. One advantage of the spoke cavity geometry is that couplers can be placed on the outer body of the cavity rather than in the beam line space. We present an overview of the HOM properties of spoke cavities and methods for suppressing the most harmful ones.
Multiband S Wave Topological Superconductors: Role Of Dimensionality And Magnetic Field Response, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Multiband S Wave Topological Superconductors: Role Of Dimensionality And Magnetic Field Response, Shusa Deng, Gerardo Ortiz, Lorenza Viola
Open Dartmouth: Faculty Open Access Scholarship
We further investigate a class of timereversalinvariant twoband swave topological superconductors introduced earlier [Deng, Viola, and Ortiz, Phys. Rev. Lett. 108, 036803 (2012)]. Provided that a sign reversal between the two superconducting pairing gaps is realized, the topological phase diagram can be determined exactly (within mean field) in one and two dimensions as well as in three dimensions upon restricting to the excitation spectrum of timereversalinvariant momentum modes. We show how, in the presence of timereversal symmetry, Z2 invariants that distinguish between trivial and nontrivial quantum phases can be constructed by considering only one of the Kramers’ sectors in which ...
Imaging The Anisotropic Nonlinear Meissner Effect In Nodal Yba _{2}Cu_{3}O_{7Δ} ThinFilm Superconductors, Alexander P. Zhuravel, Behnood G. Ghamsari, Cihan Kurter, Philipp Jung, Stephen K. Remillard, John A. Abrahams, Alexander V. Lukashenko, Alexey V. Ustinov, Steven Mark Anlage
Imaging The Anisotropic Nonlinear Meissner Effect In Nodal Yba 2Cu3O7Δ ThinFilm Superconductors, Alexander P. Zhuravel, Behnood G. Ghamsari, Cihan Kurter, Philipp Jung, Stephen K. Remillard, John A. Abrahams, Alexander V. Lukashenko, Alexey V. Ustinov, Steven Mark Anlage
Physics Faculty Research & Creative Works
We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact selfresonant spiral structure, excited near resonance in the radiofrequency range, and scanned with a focused laser beam perturbation. At low temperatures, directiondependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal ...
Switching Nonlinearity In A SuperconductorEnhanced Metamaterial, Cihan Kurter, Philippe Tassin, Alexander P. Zhuravel, Lei Zhang, Thomas Koschny, Alexey V. Ustinov, Costas M. Soukoulis, Steven M. Anlage
Switching Nonlinearity In A SuperconductorEnhanced Metamaterial, Cihan Kurter, Philippe Tassin, Alexander P. Zhuravel, Lei Zhang, Thomas Koschny, Alexey V. Ustinov, Costas M. Soukoulis, Steven M. Anlage
Physics Faculty Research & Creative Works
We demonstrate a nonlinear metamaterial that can be switched between low and high transmission by controlling the power level of the incident beam. The origin of this nonlinear response is the superconducting Nb thin film employed in the metamaterial structure. We show that with moderate RF power of about 22 dBm it is possible to quench the superconducting state as a result of extremely strong current densities at the corners of the metamaterial's splitring resonators. We measure a transmission contrast of 10 dB and a change in group delay of 70 ns between the low and high power states.
Majorana Modes In TimeReversal Invariant S Wave Topological Superconductors, Shusa Deng, Lorenza Viola, Gerardo Ortiz
Majorana Modes In TimeReversal Invariant S Wave Topological Superconductors, Shusa Deng, Lorenza Viola, Gerardo Ortiz
Open Dartmouth: Faculty Open Access Scholarship
We present a timereversal invariant swave superconductor supporting Majorana edge modes. The multiband character of the model together with spinorbit coupling are key to realizing such a topological superconductor. We characterize the topological phase diagram by using a partial Chern number sum, and show that the latter is physically related to the parity of the fermion number of the timereversal invariant modes. By taking the selfconsistency constraint on the swave pairing gap into account, we also establish the possibility of a direct topological superconductortotopological insulator quantum phase transition.
Nonlinear Hydrodynamics Of Disentangled FluxLine Liquids, Panayotis Benetatos, M. Cristina Marchetti
Nonlinear Hydrodynamics Of Disentangled FluxLine Liquids, Panayotis Benetatos, M. Cristina Marchetti
Physics
In this paper we use nonGaussian hydrodynamics to study the magnetic response of a fluxline liquid in the mixed state of a typeII superconductor. Both the derivation of our model, which goes beyond conventional Gaussian flux liquid hydrodynamics, and its relationship to other approaches used in the literature are discussed. We focus on the response to a transverse tilting field which is controlled by the tilt modulus, c44, of the flux array. We show that interaction effects can enhance c44 even in infinitely thick clean materials. This enhancement can be interpreted as the appearance of a disentangled fluxliquid fraction. In ...
Theory Of DoubleSided Flux Decorations, M. Cristina Marchetti, David R. Nelson
Theory Of DoubleSided Flux Decorations, M. Cristina Marchetti, David R. Nelson
Physics
A novel twosided Bitter decoration technique was recently employed by Yao et al. to study the structure of the magnetic vortex array in hightemperature superconductors. Here we discuss the analysis of such experiments. We show that twosided decorations can be used to infer {\it quantitative} information about the bulk properties of flux arrays, and discuss how a least squares analysis of the local density differences can be used to bring the two sides into registry. Information about the tilt, compressional and shear moduli of bulk vortex configurations can be extracted from these measurements.
Classical Analogue Of Electromagnetically Induced Transparency With A MetalSuperconductor Hybrid Metamaterial, Cihan Kurter, Philippe Tassin, Lei Zhang, Thomas Koschny, Alexander P. Zhuravel, Alexey V. Ustinov, Steven Mark Anlage, Costas M. Soukoulis
Classical Analogue Of Electromagnetically Induced Transparency With A MetalSuperconductor Hybrid Metamaterial, Cihan Kurter, Philippe Tassin, Lei Zhang, Thomas Koschny, Alexander P. Zhuravel, Alexey V. Ustinov, Steven Mark Anlage, Costas M. Soukoulis
Physics Faculty Research & Creative Works
Metamaterials are engineered materials composed of small electrical circuits producing novel interactions with electromagnetic waves. Recently, a new class of metamaterials has been created to mimic the behavior of media displaying electromagnetically induced transparency (EIT). Here we introduce a planar EIT metamaterial that creates a very large loss contrast between the dark and radiative resonators by employing a superconducting Nb film in the dark element and a normalmetal Au film in the radiative element. Below the critical temperature of Nb, the resistance contrast opens up a transparency window along with a large enhancement in group delay, enabling a significant slowdown ...
MillimeterWave Study Of London Penetration Depth Temperature Dependence In Ba(Fe0.926co0.074)2as2 Single Crystal, A. A. Barannik, N. T. Cherpak, Ni Ni, Makariy A. Tanatar, S. A. Vitusevich, V. N. Skresanov, Paul C. Canfield, Ruslan Prozorov, V. V. Glamazdin, K. I. Torokhtii
MillimeterWave Study Of London Penetration Depth Temperature Dependence In Ba(Fe0.926co0.074)2as2 Single Crystal, A. A. Barannik, N. T. Cherpak, Ni Ni, Makariy A. Tanatar, S. A. Vitusevich, V. N. Skresanov, Paul C. Canfield, Ruslan Prozorov, V. V. Glamazdin, K. I. Torokhtii
Ames Laboratory Publications
Inplane surface Kaband microwave impedance of optimally dopedsingle crystals of the Febased superconductor Ba(Fe_{0.926}Co_{0.074})_{2}As_{2} (T_{c} = 22.8 K) was measured. Sensitive sapphire disk quasioptical resonator with highT_{c} cuprate conducting endplates was developed specially for Fepnictide superconductors. It allowed finding temperature variation of London penetration depth in a form of power law, namely Δλ(T) ∼ T^{n} with n = 2.8 from low temperatures up to at least 0.6T_{c} consisted with radiofrequency measurements. This exponent points towards nodeless state with pairbreaking scattering, which can support one ...
Bandwidth Tuning Triggers Interplay Of Charge Order And Superconductivity In TwoDimensional Organic Materials, S. Kaiser, M. Dressel, Y. Sun, A. Greco, J. A. Schlueter, Gary L. Gard, N. Drichko
Bandwidth Tuning Triggers Interplay Of Charge Order And Superconductivity In TwoDimensional Organic Materials, S. Kaiser, M. Dressel, Y. Sun, A. Greco, J. A. Schlueter, Gary L. Gard, N. Drichko
Chemistry Faculty Publications and Presentations
We observe chargeorder fluctuations in the quasitwodimensional organic superconductor β″(BEDTTTF)₂SF₅CH₂CF₂SO₃, both by means of vibrational spectroscopy, locally probing the fluctuating charge order, and by investigating the inplane dynamical response by infrared reflectance spectroscopy. The decrease of the effective electronic interaction in an isostructural metal suppresses both chargeorder fluctuations and superconductivity, pointing to their interplay. We compare the results of our experiments with calculations on the extended Hubbard model.
Dynamical Conductivity At The Dirty SuperconductorMetal Quantum Phase Transition, Adrian Del Maestro, Bernd Rosenow, Jose A. Hoyos, Thomas Vojta
Dynamical Conductivity At The Dirty SuperconductorMetal Quantum Phase Transition, Adrian Del Maestro, Bernd Rosenow, Jose A. Hoyos, Thomas Vojta
Physics Faculty Research & Creative Works
We study the transport properties of ultrathin disordered nanowires in the neighborhood of the superconductormetal quantum phase transition. To this end we combine numerical calculations with analytical strongdisorder renormalization group results. The quantum critical conductivity at zero temperature diverges logarithmically as a function of frequency. In the metallic phase, it obeys activated scaling associated with an infiniterandomness quantum critical point. We extend the scaling theory to higher dimensions and discuss implications for experiments.
Anomalously Elastic Intermediate Phase In Randomly Layered Superfluids, Superconductors, And Planar Magnets, Priyanka Mohan, Paul M. Goldbart, Rajesh Narayanan, John Toner, Thomas Vojta
Anomalously Elastic Intermediate Phase In Randomly Layered Superfluids, Superconductors, And Planar Magnets, Priyanka Mohan, Paul M. Goldbart, Rajesh Narayanan, John Toner, Thomas Vojta
Physics Faculty Research & Creative Works
We show that layered quenched randomness in planar magnets leads to an unusual intermediate phase between the conventional ferromagnetic lowtemperature and paramagnetic hightemperature phases. In this intermediate phase, which is part of the Griffiths region, the spinwave stiffness perpendicular to the random layers displays anomalous scaling behavior, with a continuously variable anomalous exponent, while the magnetization and the stiffness parallel to the layers both remain finite. Analogous results hold for superfluids and superconductors. We study the two phase transitions into the anomalous elastic phase, and we discuss the universality of these results, and implications of finite sample size as well ...
Miniaturized Superconducting Metamaterials For Radio Frequencies, Cihan Kurter, John A. Abrahams, Steven Mark Anlage
Miniaturized Superconducting Metamaterials For Radio Frequencies, Cihan Kurter, John A. Abrahams, Steven Mark Anlage
Physics Faculty Research & Creative Works
We have developed a lowloss, ultrasmall radio frequency (rf) metamaterial operating at ~76 MHz. This miniaturized medium is made up of planar spiral elements with diameter as small as ~λ/658 (λ is the free space wavelength), fashioned from Nb thin films on quartz substrates. The transmission data are examined below and above the superconducting transition temperature of Nb for both a single spiral and a one dimensional array. The validity of the design is tested through numerical simulations and good agreement is found. We discuss how superconductors enable such a compact design in the rf with high loadedquality factor ...
Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock
Upper Limits On A Possible Gluon Mass, Shmuel Nussinov, Robert Shrock
Mathematics, Physics, and Computer Science Faculty Articles and Research
We analyze upper limits on a possible gluon mass, mg. We first discuss various ways to modify quantum chromodynamics to include m(g) not equal 0, including a bare mass, a Higgs mechanism, and dynamical breaking of color SU(3)(c). From an examination of experimental data, we infer an upper limit m(g) < O(1) MeV. As part of our analysis, we show that a claim, hitherto unrefuted in the literature, of a much stronger upper limit on m(g), is invalid. We discuss subtleties in interpreting gluon mass limits in view of the fact that at scales below Lambda(QCD), quantum chromodynamics is strongly coupled, perturbation theory is not reliable, and the physics is not accurately described in terms of the Lagrangian degrees of freedom, including gluons. We also point out a fundamental difference in the behavior of quantum chromodynamics with a nonzero gluon mass and a weakly coupled gauge theory with a gauge boson mass.
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: I. Echo Scheme, A. D. Armour, M. P. Blencowe
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: I. Echo Scheme, A. D. Armour, M. P. Blencowe
Open Dartmouth: Faculty Open Access Scholarship
We propose a scheme in which the quantum coherence of a nanomechanical resonator can be probed using a superconducting qubit. We consider a mechanical resonator coupled capacitively to a Cooper pair box and assume that the superconducting qubit is tuned to the degeneracy point so that its coherence time is maximized and the electromechanical coupling can be approximated by a dispersive Hamiltonian. When the qubit is prepared in a superposition of states, this drives the mechanical resonator progressively into a superposition which in turn leads to apparent decoherence of the qubit. Applying a suitable control pulse to the qubit allows ...
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: Ii. Implementation, M. P. Blencowe, A. D. Armour
Probing The Quantum Coherence Of A Nanomechanical Resonator Using A Superconducting Qubit: Ii. Implementation, M. P. Blencowe, A. D. Armour
Open Dartmouth: Faculty Open Access Scholarship
We describe a possible implementation of the nanomechanical quantum superposition generation and detection scheme described in the preceding, companion paper (Armour A D and Blencowe M P 2008 New. J. Phys. 10 095004). The implementation is based on the circuit quantum electrodynamics (QED) setup, with the addition of a mechanical degree of freedom formed out of a suspended, doublyclamped segment of the superconducting loop of a dc SQUID located directly opposite the centre conductor of a coplanar waveguide (CPW). The relative merits of two SQUID based qubit realizations are addressed, in particular a capacitively coupled charge qubit and inductively coupled ...
Quantum Analysis Of A Nonlinear Microwave CavityEmbedded Dc Squid Displacement Detector, P. D. Nation, M. P. Blencowe, E. Buks
Quantum Analysis Of A Nonlinear Microwave CavityEmbedded Dc Squid Displacement Detector, P. D. Nation, M. P. Blencowe, E. Buks
Open Dartmouth: Faculty Open Access Scholarship
We carry out a quantum analysis of a dc superconducting quantum interference device (SQUID) mechanical displacement detector, comprising a SQUID with mechanically compliant loop segment, which is embedded in a microwave transmission line resonator. The SQUID is approximated as a nonlinear currentdependent inductance, inducing an external flux tunable nonlinear Duffing selfinteraction term in the microwave resonator mode equation. Motion of the compliant SQUID loop segment is transduced inductively through changes in the external flux threading SQUID loop, giving a ponderomotive radiation pressuretype coupling between the microwave and mechanical resonator modes. Expressions are derived for the detector signal response and noise ...