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Topic Area: Condensed Matter Physics

Displaying records 51 to 60 of 97 records.
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51. Total-dielectric-function Approach to Electron and Phonon Response in Solids
Topic: Condensed Matter Physics
Published: 1/1/1995
Authors: David R. Penn, S Lewis, Marvin Cohen
Abstract: The interaction between two test charges, the response of a solid to an external field, and the normal modes of the solid can be determined from a total dielectric function that includes both electronic and lattice polarizabilities as well as local- ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620441

52. Inverse Isotope Effects and Models for High-Tc Superconductivity
Topic: Condensed Matter Physics
Published: 1/1/1993
Authors: David R. Penn, Marvin Cohen, V Crespi
Abstract: A model for high-temperature superconductivity with a mass-independent electronic mechanism in conjunction with a moderate amount of electron-phonon coupling has previously been shown to be inconsistent with experimental constraints on T^dc^, the iso ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620413

53. Effects of Broadening on the BCS Theory in the Presence of Van Hove Singularities
Topic: Condensed Matter Physics
Published: 1/1/1992
Authors: David R. Penn, Marvin Cohen
Abstract: There have been recent suggestions that high-Tc superconductivity can be understood in terms of conventional BCS theory if there is a logarithmic Van Hove singularity in the electron density of states near the Fermi energy as suggested by band theory ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620408

54. Photo-Induced Resonant Tunneling Treated by the Extended Transfer Hamiltonian Method
Topic: Condensed Matter Physics
Published: 1/1/1992
Authors: S Apell, David R. Penn
Abstract: A method, originally due to Heitler, is utilized to extend the transfer Hamiltonian description to resonant tunneling for the purpose of calculating transition probabilities and general frequency response characteristics of coupled systems. The scann ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620402

55. Anharmonic Phonons and the Isotope Effect in Superconductivity
Topic: Condensed Matter Physics
Published: 1/1/1991
Authors: V Crespi, Marvin Cohen, David R. Penn
Abstract: Anharmonic interionic potentials are examined in an Einstein model to study the unusual isotope-effect exponents for the high-T(c) oxides. The mass dependences of the electron-phonon coupling constant {lambda} and the average phonon frequency square- ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620376

56. Experimental Constraints on Some Mechanisms for High-Temperature Superconductivity
Topic: Condensed Matter Physics
Published: 1/1/1991
Authors: I Barbee, Marvin Cohen, David R. Penn
Abstract: Since its discovery, many mechanisms have been suggested to explain the phenomenon of high-temperature superconductivity in oxides. We propose that experimental data, along with theoretical models, can place constraints on or exclude many of these me ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620389

57. Limitations on a Combined Phonon -- Non-Phonon Mechanism for Superconductivity Bi^d2^Sr^d3^Ca^d1^Cu^d2^O^dx^
Topic: Condensed Matter Physics
Published: 1/1/1991
Authors: I Barbee, Marvin Cohen, David R. Penn
Abstract: ^d^^d^^d^^d^^d^ Despite the large number of theories proposed to explain high-temperature superconductivity, no clear explanation of its origin exists. Experimental data such as the isotope effect {alpha} and the gap ratio 2{Delta}/k^db^T^dc^ can be ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620401

58. Extended Transfer Hamiltonian Method for Resonant Tunneling
Topic: Condensed Matter Physics
Published: 12/10/1990
Authors: S Apell, E Albertsson, David R. Penn
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620364

59. Limitations on Electronic Mechanisms for High Temperature Superconducting Oxides
Topic: Condensed Matter Physics
Published: 1/1/1990
Authors: David R. Penn, Marvin Cohen, I Barbee
Abstract: The effects of electronic mechanisms for electron pairing in high temperature superconducting oxides on both the transition temperature T^dc^ and the isotope effect parameter {alpha} are considered. It is shown that for the higher T^dc^ oxides, meas ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620382

60. Weak versus Strong Coupling Theory for Bi^d2^Sr^d2^CaCu^d2^O^d8^
Topic: Condensed Matter Physics
Published: 1/1/1990
Authors: Marvin Cohen, David R. Penn
Abstract: ^d^^d^^d^^d^ The latest optical determination of the superconducting-gap function for Bi^d2^Sr^d2^CaCu^d2^O^d8^ is consistent with weak-coupling theory. In contrast, a large discontinuity in heat-capacity data suggests strong-coupling superconductivi ...
http://www.nist.gov/manuscript-publication-search.cfm?pub_id=620366