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Full-Text Articles in Physics
Ultra-Thin Perfect Absorber Employing A Tunable Phase Change Material, Mikhail A. Kats, Deepika Sharma, (...), M. M. Qazilbash, Et Al.
Ultra-Thin Perfect Absorber Employing A Tunable Phase Change Material, Mikhail A. Kats, Deepika Sharma, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We show that perfect absorption can be achieved in a system comprising a single lossy dielectric layer of thickness much smaller than the incident wavelength on an opaque substrate by utilizing the nontrivial phase shifts at interfaces between lossy media. This design is implemented with an ultra-thin (∼λ/65) vanadium dioxide (VO2) layer on sapphire, temperature tuned in the vicinity of the VO2 insulator-to-metal phase transition, leading to 99.75% absorption at λ = 11.6 μm. The structural simplicity and large tuning range (from ∼80% to 0.25% in reflectivity) are promising for thermal emitters, modulators, and bolometers.
Universal Conductance Fluctuations In Dirac Materials In The Presence Of Long-Range Disorder, Enrico Rossi, J. H. Bardarson, M. S. Fuhrer, S. Das Sarma
Universal Conductance Fluctuations In Dirac Materials In The Presence Of Long-Range Disorder, Enrico Rossi, J. H. Bardarson, M. S. Fuhrer, S. Das Sarma
Arts & Sciences Articles
We study quantum transport in Dirac materials with a single fermionic Dirac cone (strong topological insulators and graphene in the absence of intervalley coupling) in the presence of non-Gaussian long-range disorder. We show, by directly calculating numerically the conductance fluctuations, that in the limit of very large system size and disorder strength, quantum transport becomes universal. However, a systematic deviation away from universality is obtained for realistic system parameters. By comparing our results to existing experimental data on 1/f noise, we suggest that many of the graphene samples studied to date are in a nonuniversal crossover regime of conductance fluctuations.
Insulator-To-Metal Transition And Correlated Metallic State Of V 2 O 3 Investigated By Optical Spectroscopy, M. K. Stewart, D. Brownstead, (...), M. M. Qazilbash, Et Al.
Insulator-To-Metal Transition And Correlated Metallic State Of V 2 O 3 Investigated By Optical Spectroscopy, M. K. Stewart, D. Brownstead, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
The optical properties of V2O3 thin films are investigated across the insulator-to-metal transition and in the metallic state. The spectral weight transfer observed across the transition, over an energy scale of 5 eV, is consistent with the Mott-Hubbard model for correlated electron systems. In the metallic phase, a strong Drude peak is observed, which exhibits a pronounced temperature dependence related to the transfer of states from the Hubbard bands to the quasiparticle peaks as the temperature is reduced. The analysis of the far-infrared spectra reveals signatures of strong electronic correlations in V2O3. Finally, a comparison to VO2 data is presented.
Coupled-Channel Theory Of Photoionization Microscopy, L. B. Zhao, I. I. Fabrikant, John B. Delos, F. Lepine, S. Cohen, C. Bordas
Coupled-Channel Theory Of Photoionization Microscopy, L. B. Zhao, I. I. Fabrikant, John B. Delos, F. Lepine, S. Cohen, C. Bordas
Arts & Sciences Articles
We develop a quantum-mechanical coupled-channel theory to simulate spatial distributions of electron current densities, produced in photoionization for nonhydrogenic atoms in the presence of a uniform external electric field. The coupled Schrodinger equations are numerically solved using the renormalized Numerov method. The expression for the outgoing wave function for photoelectrons ejected from the nonhydrogenic atomic source is derived. The theory is applied to investigations of photoionization for ground-state Li atoms. The distributions of electron current densities are computed and compared to the corresponding experimental images. Excellent agreement is obtained. It is, furthermore, found that the presence of the nonhydrogenic residual …
Electronic Correlations And Unconventional Spectral Weight Transfer In The High-Temperature Pnictide Bafe2-Xcoxas2 Superconductor Using Infrared Spectroscopy, A. A. Schafgans, S. J. Moon, (...), M. M. Qazilbash, Et Al.
Electronic Correlations And Unconventional Spectral Weight Transfer In The High-Temperature Pnictide Bafe2-Xcoxas2 Superconductor Using Infrared Spectroscopy, A. A. Schafgans, S. J. Moon, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We report an infrared optical study of the pnictide high-temperature superconductor BaFe1.84Co0.16As2 and its parent compound BaFe2As2. We demonstrate that electronic correlations are moderately strong and do not change across the spin-density wave transition or with doping. By examining the energy scale and direction of spectral weight transfer, we argue that Hund's coupling J is the primary mechanism that gives rise to correlations.
Breath-By-Breath Analysis Of Cardiorespiratory Interaction For Quantifying Developmental Maturity In Premature Infants, Matthew T. Clark, Craig G. Rusin, John L. Hudson, Hoshik Lee, John B. Delos, Et Al.
Breath-By-Breath Analysis Of Cardiorespiratory Interaction For Quantifying Developmental Maturity In Premature Infants, Matthew T. Clark, Craig G. Rusin, John L. Hudson, Hoshik Lee, John B. Delos, Et Al.
Arts & Sciences Articles
Breath-by-breath analysis of cardiorespiratory interaction for quantifying developmental maturity in premature infants. J Appl Physiol 112: 859-867, 2012. First published December 15, 2011; doi:10.1152/japplphysiol.01152.2011.-In healthy neonates, connections between the heart and lungs through brain stem chemosensory pathways and the autonomic nervous system result in cardiorespiratory synchronization. This interdependence between cardiac and respiratory dynamics can be difficult to measure because of intermittent signal quality in intensive care settings and variability of heart and breathing rates. We employed a phase-based measure suggested by Sch fer and coworkers (Sch fer C, Rosenblum MG, Kurths J, Abel HH. Nature 392: 239-240, 1998) to obtain …
Chaotic Escape From An Open Vase-Shaped Cavity. I. Numerical And Experimental Results, Jaison Allen Novick, Matthew L. Keeler, Joshua Geifer
Chaotic Escape From An Open Vase-Shaped Cavity. I. Numerical And Experimental Results, Jaison Allen Novick, Matthew L. Keeler, Joshua Geifer
Arts & Sciences Articles
No abstract provided.
Chaotic Escape From An Open Vase-Shaped Cavity. I. Numerical And Experimental Results, Jaison Novick, Matthew L. Keeler, Joshua Giefer, John B. Delos
Chaotic Escape From An Open Vase-Shaped Cavity. I. Numerical And Experimental Results, Jaison Novick, Matthew L. Keeler, Joshua Giefer, John B. Delos
Arts & Sciences Articles
We present part I in a two-part study of an open chaotic cavity shaped as a vase. The vase possesses an unstable periodic orbit in its neck. Trajectories passing through this orbit escape without return. For our analysis, we consider a family of trajectories launched from a point on the vase boundary. We imagine a vertical array of detectors past the unstable periodic orbit and, for each escaping trajectory, record the propagation time and the vertical detector position. We find that the escape time exhibits a complicated recursive structure. This recursive structure is explored in part I of our study. …
Chaotic Escape From An Open Vase-Shaped Cavity. Ii. Topological Theory, Jaison Allen Novick, John B. Delos
Chaotic Escape From An Open Vase-Shaped Cavity. Ii. Topological Theory, Jaison Allen Novick, John B. Delos
Arts & Sciences Articles
We present part II of a study of chaotic escape from an open two-dimensional vase-shaped cavity. A surface of section reveals that the chaotic dynamics is controlled by a homoclinic tangle, the union of stable and unstable manifolds attached to a hyperbolic fixed point. Furthermore, the surface of section rectifies escape-time graphs into sequences of escape segments; each sequence is called an epistrophe. Some of the escape segments (and therefore some of the epistrophes) are forced by the topology of the dynamics of the homoclinic tangle. These topologically forced structures can be predicted using the method called homotopic lobe dynamics …