Open Access. Powered by Scholars. Published by Universities.®
- Discipline
-
- Other Physics (6)
- Condensed Matter Physics (5)
- Engineering (4)
- Fluid Dynamics (4)
- Chemistry (3)
-
- Electrical and Computer Engineering (2)
- Optics (2)
- Other Chemistry (2)
- Quantum Physics (2)
- Analysis (1)
- Applied Mathematics (1)
- Atomic, Molecular and Optical Physics (1)
- Biological and Chemical Physics (1)
- Electrical and Electronics (1)
- Engineering Physics (1)
- Mathematics (1)
- Mechanical Engineering (1)
- Medical Biophysics (1)
- Medical Sciences (1)
- Medical Specialties (1)
- Medicine and Health Sciences (1)
- Nanoscience and Nanotechnology (1)
- Other Applied Mathematics (1)
- Other Physical Sciences and Mathematics (1)
- Partial Differential Equations (1)
- Physical Chemistry (1)
- Radiology (1)
- VLSI and Circuits, Embedded and Hardware Systems (1)
- Keyword
-
- Articles (15)
- La₂₋ₓSrₓCuO₄ (4)
- Bi₂Sr₂CaCu₂O₈+δ (3)
- Muffin-tin alloys (3)
- STS (3)
-
- Scanning tunneling spectroscopy (3)
- ARPES (2)
- Angle-resolved photoemission (2)
- Ba₁₋ₓKₓBiO₃ (2)
- Bias (2)
- Bubble dynamics (2)
- Coherent-potential approximation (2)
- Compton profiles (2)
- Compton scattering (2)
- Conference Proceedings (2)
- Control (2)
- Cu (2)
- Dry friction (2)
- Electric (2)
- Electrons (2)
- Exchange (2)
- Exchange bias (2)
- Fermi energy (2)
- Fermi surface (2)
- Infectious disease (2)
- Magnetism (2)
- Matrix element effects (2)
- Sonochemistry (2)
- Sonoluminescence (2)
- X-ray absorption near edge structure (2)
- Publication
-
- Arun Bansil (13)
- Christian Binek (13)
- Robert Markiewicz (8)
- Alessandro Vespignani (7)
- Brian Storey (5)
-
- Rebecca J. Christianson (3)
- Siti Rohana Majid (3)
- Bernardo Barbiellini (2)
- Bradley Minch (2)
- Hsin Lin (2)
- Thushara A. Perera (2)
- Yevgeniya V. Zastavker (2)
- Chance Hoellwarth (1)
- Christopher Daly (1)
- Christopher Lee (1)
- David V. Kerns (1)
- Haim Goldberg (1)
- Jeffrey Sokoloff (1)
- Jeremy R. Gulley (1)
- Jessica Townsend (1)
- Ralph Saxton (1)
- Srinivas Sridhar (1)
- Stephen Holt (1)
Articles 1 - 30 of 73
Full-Text Articles in Physics
Ultrafast Laser-Induced Damage And The Influence Of Spectral Effects, Jeremy Gulley
Ultrafast Laser-Induced Damage And The Influence Of Spectral Effects, Jeremy Gulley
Jeremy R. Gulley
Numerous studies have investigated the prerequisite role of photoionization in ultrafast laser-induced damage (LID) of bulk dielectrics. This study examines the role of spectral width and instantaneous laser frequency in LID using a frequency dependent multiphoton ionization (MPI) model and numerical simulation of initially 800 nm laser pulses propagating through fused silica. Assuming a band gap of 9 eV, MPI by an 800 nm field is a six-photon process, but when the instantaneous wavelength is greater than 827 nm an additional photon is required for photoionization, reducing the probability of the event by many orders of magnitude. Simulation results suggest …
Super-Resolution Imaging Using A Three-Dimensional Metamaterials Nanolens, B. Casse, W. Lu, Y. Huang, E. Gultepe, L. Menon, S. Sridhar
Super-Resolution Imaging Using A Three-Dimensional Metamaterials Nanolens, B. Casse, W. Lu, Y. Huang, E. Gultepe, L. Menon, S. Sridhar
Srinivas Sridhar
Super-resolution imaging beyond Abbe's diffraction limit can be achieved by utilizing an optical medium or "metamaterial" that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite …
Adaptive Circuits Using Pfet Floating-Gate Devices, Paul Hasler, Bradley Minch, Chris Diorio
Adaptive Circuits Using Pfet Floating-Gate Devices, Paul Hasler, Bradley Minch, Chris Diorio
Bradley Minch
In this paper, we describe our floating-gate pFET device, with its many circuit applications and supporting experimental measurements. We developed these devices in standard double-poly CMOS technologies by utilizing many effects inherent in these processes. We add floating-gate charge by electron tunneling, and we remove floating-gate charge by hot-electron injection. With this floating-gate technology, we cannot only build analog EEPROMs, we can also implement adaptation and learning when we consider floating-gate devices to be circuit elements with important time-domain dynamics. We start by discussing non-adaptive properties of floating-gate devices and we present two representative non-adaptive applications. First, we discuss using …
A Long-Channel Model For The Asymmetric Double-Gate Mosfet Valid In All Regions Of Operation, Abhishek Kammula, Bradley Minch
A Long-Channel Model For The Asymmetric Double-Gate Mosfet Valid In All Regions Of Operation, Abhishek Kammula, Bradley Minch
Bradley Minch
We present a physically based, continuous analytical model for long-channel double-gate MOSFETs. The model is particularly well suited for implementation in circuit simulators due to the simple expressions for the current andthe continuous nature of the derivatives of the current which improves convergence behavior.
Incommensurate Spin Fluctuations In High-Transition Temperature Superconductors, Barrett Wells, Young Lee, Marc Kastner, Rebecca Christianson, Robert Birgeneau, Kazuyoshi Yamada, Yasuo Endoh, Gen Shirane
Incommensurate Spin Fluctuations In High-Transition Temperature Superconductors, Barrett Wells, Young Lee, Marc Kastner, Rebecca Christianson, Robert Birgeneau, Kazuyoshi Yamada, Yasuo Endoh, Gen Shirane
Rebecca J. Christianson
Neutron scattering experiments have revealed a fascinating interplay between the hole doping, the spin fluctuations, and the superconductivity of the cuprate superconductors. Recently, electrochemical techniques have been used to produce large single crystals of La2CuO4+ y, which has mobile oxygen dopants. Staging behavior of the excess oxygen has been demonstrated, and the low-energy spin fluctuations in stage 6 La2CuO4+ y have been measured. The spin fluctuations are incommensurate with the lattice and have spatial, energy, and temperature dependencies very much like those in La2− xSrxCuO4, with similar high transition temperature. This establishes the universality of the incommensurate spin fluctuations among …
Structures And Incommensurate Spin Excitations In Excess Oxygen-Doped La2cuo4+Y, Robert Birgeneau, Rebecca Christianson, Yasuo Endoh, Marc Kastner, Young Lee, Gen Shirane, Barrett Wells, Kazuyoshi Yamada
Structures And Incommensurate Spin Excitations In Excess Oxygen-Doped La2cuo4+Y, Robert Birgeneau, Rebecca Christianson, Yasuo Endoh, Marc Kastner, Young Lee, Gen Shirane, Barrett Wells, Kazuyoshi Yamada
Rebecca J. Christianson
Over the past decade, we have studied in detail the low-energy spin fluctuations in :a2−xSrxCuO4 for xbetween 0 and 0.18. Our experiments, as well as those by others, have revealed a fascinating interplay between the hole doping, the static and dynamic spin fluctuations and superconductivity. Recently, using electrochemical techniques, we have learned how to produce large single crystals of La2CuO4+y which are relatively homogenous. In this latter system, the dopants are characterized by annealed rather than quenched disorder. Furthermore, we have demonstrated staging behavior of the excess oxygen analogous to staging in intercalated graphite. We have now succeeded in carrying …
A Reduced Model Of Cavitation Physics For Use In Sonochemistry, Brian Storey, Andrew Szeri
A Reduced Model Of Cavitation Physics For Use In Sonochemistry, Brian Storey, Andrew Szeri
Brian Storey
Sonochemistry involves focusing acoustic energy through cavitation bubbles to increase chemical activity. The violent bubble collapses lead to temperatures of several thousand kelvin, which drive chemical reactions. In previous work, we gave a detailed computational model of a single bubble collapse, taking into account phase change, mass diffusion, heat diffusion and chemical reactions. All of these phenomena are important in determining the conditions at collapse. The present work involves development of a much simpler model that includes all the physics relevant to the determination of the reaction products. Comparisons with the more detailed computations are made; the reduced model is …
Water Vapour, Sonoluminescence And Sonochemistry, Brian Storey, Andrew Szeri
Water Vapour, Sonoluminescence And Sonochemistry, Brian Storey, Andrew Szeri
Brian Storey
Sonoluminescence is the production of light from acoustically forced bubbles; sonochemistry is a related chemical processing technique. The two phenomena share a sensitive dependence on the liquid phase. The present work is an investigation of the fate and consequences of water vapour in the interior of strongly forced argon micro–bubbles. Due to the extreme nonlinearity of the volume oscillations, excess water vapour is trapped in the bubble during a rapid inertial collapse. Water vapour is prevented from exiting by relatively slow diffusion and non–equilibrium condensation at the bubble wall. By reducing the compression heating of the mixture and through primarily …
Temperature Distribution In An Oscillatory Flow With A Sinusoidal Wall Temperature, Eduardo Ramos, Brian Storey, Fernando Sierra, Raul Zuniga, Andriy Avramenko
Temperature Distribution In An Oscillatory Flow With A Sinusoidal Wall Temperature, Eduardo Ramos, Brian Storey, Fernando Sierra, Raul Zuniga, Andriy Avramenko
Brian Storey
The temperature field generated by an oscillatory boundary layer flow in the presence of a wall with a sinusoidal temperature distribution is analyzed. A linear perturbation method is used to find closed form analytical solutions for the temperature field when the amplitude of the velocity oscillation is small. The analytical solutions only consider long-time behavior when the temperature fields oscillate with the frequency of the flow. The structure of the equation that governs the temperature correction due to convection is similar to that of diffusive waves with the solution consisting of traveling or standing waves. The temperature distribution is also …
Nonextensive Statistical Mechanics For Rotating Quasi-Two-Dimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Nonextensive Statistical Mechanics For Rotating Quasi-Two-Dimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Brian Storey
We have conducted experiments on an asymmetrically forced quasi-two-dimensional turbulent flow in a rapidly rotating annulus. Assuming conservation of potential enstrophy and energy, we maximize a nonextensive entropy function to obtain the azimuthally averaged vorticity as a function of radial position. The predicted vorticity profile is in good accord with the observations. A nonextensive formalism is appropriate because long-range correlations between small-scale vortices give rise to large coherent structures in the turbulence. We also derive probability distribution functions for the vorticity from both extensive and nonextensive entropies, and we find that the prediction from nonextensive theory is in better accord …
Radiation Dose Distributions In Three Dimensions From Tomographic Optical Density Scanning Of Polymer Gels: Ii. Optical Properties Of The Bang Polymer Gel, Yevgeniya Zastavker, Marek Maryanski, John Gore
Radiation Dose Distributions In Three Dimensions From Tomographic Optical Density Scanning Of Polymer Gels: Ii. Optical Properties Of The Bang Polymer Gel, Yevgeniya Zastavker, Marek Maryanski, John Gore
Yevgeniya V. Zastavker
A newly developed method of radiation dosimetry makes use of the optical properties of polymer gels. The dose-response mechanism relies on the production of light-scattering polymer micro-particles in the gel at each site of radiation absorption. The scattering produces an attenuation of transmitted light intensity that is directly related to the dose and independent of dose rate. For the BANG polymer gel (bis, acrylamide, nitrogen, and gelatin) the shape of the dose-response curve depends on the fraction of the cross-linking monomer in the initial mixture and on the wavelength of light. At 500 nm the attenuation coefficient (μ) increases by …
Dynamical Signature Of The Mott-Hubbard Transition In Ni(S,Se)(2), Yevgeniya Zastavker, Anke Husmann, Deborah Jin, Thomas Rosenbaum, X Yao, J Honig
Dynamical Signature Of The Mott-Hubbard Transition In Ni(S,Se)(2), Yevgeniya Zastavker, Anke Husmann, Deborah Jin, Thomas Rosenbaum, X Yao, J Honig
Yevgeniya V. Zastavker
The transition metal chalcogenide Ni(S,Se)2 is one of the few highly correlated, Mott-Hubbard systems without a strong first-order structural distortion that normally cuts off the critical behavior at the metal-insulator transition. The zero-temperature (T) transition was tuned with pressure, and significant deviations were found near the quantum critical point from the usual T1/2 behavior of the conductivity characteristic of electron-electron interactions in the presence of disorder. The transport data for pressure and temperature below 1 kelvin could be collapsed onto a universal scaling curve.
Performance Characteristics Of Nanocrystalline Diamond Vacuum Field Emission Transistor Array, S Hsu, W Kang, J Davidson, J Huang, David Kerns
Performance Characteristics Of Nanocrystalline Diamond Vacuum Field Emission Transistor Array, S Hsu, W Kang, J Davidson, J Huang, David Kerns
David V. Kerns
Nitrogen-incorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with self-aligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicon-on-insulator (SOI) substrate. The fabricated ND-VFET demonstrates gate-controlled emission current with good signal amplification characteristics. The dc characteristics of the ND-VFET show well-defined cutoff, linear, and saturation regions with low gate turn-on voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the ND-VFET is measured, and the experimental data are analyzed using a modified small signal circuit model. …
Oxygen Line Mapping Of Sn 1006 With Suzaku, Aya Bamba, Hiroya Yamaguchi, Katsuji Koyama, Junko Hiraga, Stephen Holt, John Hughes, Hideaki Katagiri, Jun Kataoka, Satoru Katsuda, Shunji Kitamoto, Motohide Kokubun, Hironori Matsumoto, Emi Miyata, Koji Mori, Hiroshi Nakajima, Masanobu Ozaki, Robert Petre, Akiko Sekiguchi, Tadayuki Takahashi, Takaaki Tanaka, Yukikatsu Terada, Hiroshi Tomida, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Yasunobu Uchiyama, Masaru Ueno, Shin Watanabe
Oxygen Line Mapping Of Sn 1006 With Suzaku, Aya Bamba, Hiroya Yamaguchi, Katsuji Koyama, Junko Hiraga, Stephen Holt, John Hughes, Hideaki Katagiri, Jun Kataoka, Satoru Katsuda, Shunji Kitamoto, Motohide Kokubun, Hironori Matsumoto, Emi Miyata, Koji Mori, Hiroshi Nakajima, Masanobu Ozaki, Robert Petre, Akiko Sekiguchi, Tadayuki Takahashi, Takaaki Tanaka, Yukikatsu Terada, Hiroshi Tomida, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Yasunobu Uchiyama, Masaru Ueno, Shin Watanabe
Stephen Holt
SN1006 is one of the supernova remnants (SNRs) with relatively low-temperature electrons, considering the young age of just 1000 years. We carried out SN1006 mapping observations with the X-ray Imaging Spectrometers (XIS) and the Hard X-ray Detector (HXD) onboard Suzaku, the fifth Japanese X-ray satellite. Thanks to the excellent spectral resolution of XIS in the soft X-ray band, H-like and He-like oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region …
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Rebecca J. Christianson
In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate.Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present …
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Jessica Townsend
In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate.Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present …
Non-Linear Dynamic Intertwining Of Rods With Self-Contact, Christopher Lee, Sachin Goyal, Noel Perkins
Non-Linear Dynamic Intertwining Of Rods With Self-Contact, Christopher Lee, Sachin Goyal, Noel Perkins
Christopher Lee
Twisted marine cables on the sea floor can form highly contorted three-dimensional loops that resemble tangles. Such tangles or ‘hockles’ are topologically equivalent to the plectomenes that form in supercoiled DNA molecules. The dynamic evolution of these intertwined loops is studied herein using a computationalrod model that explicitly accounts for dynamicself-contact. Numerical solutions are presented for an illustrative example of a long rod subjected to increasing twist at one end. The solutions reveal the dynamicevolution of the rod from an initially straight state, through a buckled state in the approximate form of a helix, through the dynamic collapse of this …
Tests Of A Novel Technique For Finding Galaxies In Millimeter Wavelength Maps, Thushara Perera, Alejandro Mancera, '15
Tests Of A Novel Technique For Finding Galaxies In Millimeter Wavelength Maps, Thushara Perera, Alejandro Mancera, '15
Thushara A. Perera
No abstract provided.
X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr
X-Ray Absorption Near-Edge Spectra Of Overdoped La₂₋ₓsrₓcuo₄ High-T(C) Superconductors, Towfiq Ahmed, Tanmoy Das, J. Kas, B. Barbiellini, Fernando Vila, R. Markiewicz, A. Bansil, J. Rehr
Bernardo Barbiellini
We present results for realistic modeling of the x-ray absorption near edge structure (XANES) of the overdoped high-Tc superconductor La₂₋ₓSrₓCuO₄ in the hole doping range x = 0.20 - 0.30. Our computations are based on a real-space Green's function approach in which strong-correlation effects are taken into account in terms of a doping-dependent self-energy. The predicted O K-edge XANES is found to be in good accord with the corresponding experimental results in this overdoped regime. We find that the low energy spectra are dominated by the contribution of O atoms in the cuprate planes, with little contribution from apical O …
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Bernardo Barbiellini
We present all-electron computations of the three-dimensional (3D) Fermi surfaces (FS’s) in Ba₁₋ₓKₓBiO₃ for a number of different compositions based on the self-consistent Korringa-Kohn-Rostoker coherent-potential-approximation approach for incorporating the effects of Ba/K substitution. By assuming a simple cubic structure throughout the composition range, the evolution of the nesting and other features of the FS of the underlying pristine phase is correlated with the onset of various structural transitions with K doping. A parametrized scheme for obtaining an accurate 3D map of the FS in Ba₁₋ₓKₓBiO₃ for an arbitrary doping level is developed. We remark on the puzzling differences between the …
Surface Roughness And Dry Friction, J. Sokoloff
Surface Roughness And Dry Friction, J. Sokoloff
Jeffrey Sokoloff
Persson's multiscale contact mechanics theory combined with a multiscale Brillouin-Prandtl-Tomlinson model is used to show that on the basis of these models “dry friction” [i.e., kinetic friction that remains at exceedingly small velocities (but still above the creep range) close to its value at higher velocities] should almost always occur for self-affine surfaces when the dominant interaction between two surfaces in contact is due to interatomic hard core repulsion, except for extremely smooth surfaces (i.e., surfaces with a Hurst index very close to 1).
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. Mijnarends, R. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. Eijt, H. Schut, K. Yamada, A. Bansil
Bulk Fermi Surface And Momentum Density In Heavily Doped La₂₋ₓsrₓcuo₄ Using High-Resolution Compton Scattering And Positron Annihilation Spectroscopies, W. Al-Sawai, B. Barbiellini, Y. Sakurai, M. Itou, P. Mijnarends, R. Markiewicz, S. Kaprzyk, S. Wakimoto, M. Fujita, S. Basak, H. Lin, Yung Jui Wang, S. Eijt, H. Schut, K. Yamada, A. Bansil
Robert Markiewicz
We have observed the bulk Fermi surface (FS) in an overdoped (x=0.3) single crystal of La₂₋ₓSrₓCuO₄ by using Compton scattering. A two-dimensional (2D) momentum density reconstruction from measured Compton profiles yields a clear FS signature in the third Brillouin zone along [100]. The quantitative agreement between density functional theory (DFT) calculations and momentum density experiment suggests that Fermi-liquid physics is restored in the overdoped regime. In particular the predicted FS topology is found to be in good accord with the corresponding experimental data. We find similar quantitative agreement between the measured 2D angular correlation of positron annihilation radiation (2D-ACAR) spectra …
Renormalization Of F Levels Away From The Fermi Energy In Electron Excitation Spectroscopies: Density-Functional Results For Nd2-Xcexcuo4, T. Jarlborg, B. Barbiellini, H. Lin, R. Markiewicz, A. Bansil
Renormalization Of F Levels Away From The Fermi Energy In Electron Excitation Spectroscopies: Density-Functional Results For Nd2-Xcexcuo4, T. Jarlborg, B. Barbiellini, H. Lin, R. Markiewicz, A. Bansil
Robert Markiewicz
Relaxation energies for photoemission where an occupied electronic state is excited and for inverse photoemission where an empty state is filled are calculated within the density-functional theory with application to Nd₂₋ₓCeₓCuO₄. The associated relaxation energies are obtained by computing differences in total energies between the ground state and an excited state in which one hole or one electron is added into the system. The relaxation energies of f electrons are found to be of the order of several eV’s, indicating that f bands will appear substantially away from the Fermi energy (EF) in their spectroscopic images, even if …
Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓsrₓcuo₄, S. Sahrakorpi, M. Lindroos, R. Markiewicz, A. Bansil
Evolution Of Midgap States And Residual Three Dimensionality In La₂₋ₓsrₓcuo₄, S. Sahrakorpi, M. Lindroos, R. Markiewicz, A. Bansil
Robert Markiewicz
We carry out extensive first-principles doping-dependent computations of angle-resolved photoemission (ARPES) intensities in La₂₋ₓSrₓCuO₄ over a wide range of binding energies. Intercell hopping and the associated three dimensionality, which is usually neglected in discussing cuprate physics, is shown to play a key role in shaping the ARPES spectra. Despite the obvious importance of strong coupling effects (e.g., the presence of a lower Hubbard band coexisting with midgap states in the doped insulator), a number of salient features of the experimental ARPES spectra are captured to a surprising extent when kz dispersion is properly included in the analysis.
Nodeless D-Wave Superconducting Pairing Due To Residual Antiferromagnetism In Underdoped Pr2-Xcexcuo4-Δ, Tanmoy Das, R. Markiewicz, A. Bansil
Nodeless D-Wave Superconducting Pairing Due To Residual Antiferromagnetism In Underdoped Pr2-Xcexcuo4-Δ, Tanmoy Das, R. Markiewicz, A. Bansil
Robert Markiewicz
We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr₂₋ₓCeₓCuO4-δ using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a dₓ2₋y2 pairing gap in the underlying spectrum, we find nodeless behavior of the low-T penetration depth in the underdoped case, in accord with experimental results. As doping increases, a linear-in-T behavior of the penetration depth, characteristic of d-wave pairing, emerges as the lower magnetic band crosses the Fermi level and creates a nodal Fermi surface pocket.
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Fermi-Surface Study Of Ba₁₋ₓkₓbio₃, S. Sahrakorpi, B. Barbiellini, R. Markiewicz, S. Kaprzyk, M. Lindroos, A. Bansil
Robert Markiewicz
We present all-electron computations of the three-dimensional (3D) Fermi surfaces (FS’s) in Ba₁₋ₓKₓBiO₃ for a number of different compositions based on the self-consistent Korringa-Kohn-Rostoker coherent-potential-approximation approach for incorporating the effects of Ba/K substitution. By assuming a simple cubic structure throughout the composition range, the evolution of the nesting and other features of the FS of the underlying pristine phase is correlated with the onset of various structural transitions with K doping. A parametrized scheme for obtaining an accurate 3D map of the FS in Ba₁₋ₓKₓBiO₃ for an arbitrary doping level is developed. We remark on the puzzling differences between the …
Spectral Decomposition And Matrix Element Effects In Scanning Tunneling Spectroscopy Of Bi₂Sr₂Cacu₂O₈₊Δ, Jouko Nieminen, Ilpo Suominen, R. Markiewicz, Hsin Lin, A. Bansil
Spectral Decomposition And Matrix Element Effects In Scanning Tunneling Spectroscopy Of Bi₂Sr₂Cacu₂O₈₊Δ, Jouko Nieminen, Ilpo Suominen, R. Markiewicz, Hsin Lin, A. Bansil
Robert Markiewicz
We present a Green’s function-based framework for modeling the scanning tunneling spectrum from the normal as well as the superconducting state of complex materials where the nature of the tunneling process—i.e., the effect of the tunneling “matrix element,” is properly taken into account. The formalism is applied to the case of optimally doped Bi₂Sr₂CaCu2=₂O8+δ (Bi2212) high-Tc superconductor using a large tight-binding basis set of electron and hole orbitals. The results show clearly that the spectrum is modified strongly by the effects of the tunneling matrix element and that it is not a simple replica of the local density of …
Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil
Induced Superconductivity In Noncuprate Layers Of The Bi₂Sr₂Cacu₂O₈+Δ High-Temperature Superconductor: Modeling Of Scanning Tunneling Spectra, Ilpo Suominen, Jouko Nieminen, R. Markiewicz, A. Bansil
Robert Markiewicz
We analyze how the coherence peaks observed in scanning tunneling spectroscopy (STS) of cuprate high-temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) assuming a short-range d-wave pairing interaction confined to the nearest-neighbor Cu dₓ2₋y2 orbitals. The resulting anomalous matrix elements of the Green’s function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and …
Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. Markiewicz, A. Bansil
Origin Of The Electron-Hole Asymmetry In The Scanning Tunneling Spectrum Of The High-Temperature Bi₂Sr₂Cacu₂O₈+Δ Superconductor, Jouko Nieminen, Hsin Lin, R. Markiewicz, A. Bansil
Robert Markiewicz
We have developed a material specific theoretical framework for modeling scanning tunneling spectroscopy (STS) of high-temperature superconducting materials in the normal as well as the superconducting state. Results for Bi₂Sr₂CaCu₂O₈₊δ (Bi2212) show clearly that the tunneling process strongly modifies the STS spectrum from the local density of states of the dₓ2₋y2 orbital of Cu. The dominant tunneling channel to the surface Bi involves the dₓ2₋y2 orbitals of the four neighboring Cu atoms. In accord with experimental observations, the computed spectrum displays a remarkable asymmetry between the processes of electron injection and extraction, which arises from contributions of Cu dz2 and …
Scalar Modifications To Gravity From Unparticle Effects May Be Testable, Haim Goldberg, Pran Nath
Scalar Modifications To Gravity From Unparticle Effects May Be Testable, Haim Goldberg, Pran Nath
Haim Goldberg
Interest has focused recently on low energy implications of a nontrivial scale invariant sector of an effective field theory with an IR fixed point, manifest in terms of “unparticles” with peculiar properties. If unparticle stuff exists it could couple to the stress tensor and mediate a new “fifth” force (“ungravity”). Under the assumption of strict conformal invariance in the hidden sector down to low energies, we compute the lowest order ungravity correction to the Newtonian gravitational potential and find scale invariant power law corrections of type (RG/r)2dU⁻1, where dU is an anomalous unparticle dimension and RG is a characteristic length …