Dale Harshman - Academia.edu (original) (raw)

Papers by Dale Harshman

Physical Review Letters, Nov 25, 1991

APS, Mar 1, 2001

Evidence is presented that the superconducting hole condensate generally does not reside in the c... more Evidence is presented that the superconducting hole condensate generally does not reside in the cuprate planes of high-temperature superconductors, but in the SrO layers, in the BaO layers, or in the regions of interstitial oxygen. Evidence that electrons, not holes, transfer to the cuprate planes of HgBa2Can−1CunO2+n+δ as a function of pressure, number n of layers, and increasing Tc is presented; holes transfer to the BaO layers. The hole transfer in YBa2Cu3O7 is also to the BaO layers. PrBa2Cu3O7 superconducts (as predicted) when it is free of pair-breaking PrBa defects in its BaO layers. The chosen locus of the superconductivity is consistent with the observation of magnetism in both the CuO layers and the cuprate planes of YBa2Cu3O7. Four materials were successfully predicted to superconduct by assuming that the cuprate planes are normal. There are no n-type high-temperature superconductors; Nd2−zCezCuO4 is p type and doped with interstitial oxygen. When Y+3 is replaced by Am+4, Pb2Sr2YCu3O8 becomes n...

NATO advanced study institutes series, 1987

Recently, slow positive muons (μ+) have been observed to be emitted from solid rare-gas moderator... more Recently, slow positive muons (μ+) have been observed to be emitted from solid rare-gas moderators exposed to a 4.2 MeV incident μ+ beam. Energy spectra obtained from the time of flight data indicate a maximum at ∿ 5 eV with a tail extending to higher energies. The data suggest a “hot muon” emission mechanism, implying a long diffusion length for low-energy μ+ in these solids. Of the targets measured, argon was observed to produce the highest yield (∿ 10−5slow μ+ per incident μ+), providing a useful flux for further experimentation. The discussion presented here centers around these results and their future implications for slow μ+, Mu (μ+e−) and Mu− (μ+e−e−) beams. The applications of such beams will also be discussed.

Springer eBooks, Jan 23, 2006

Evidence is presented that high-temperature superconductivity does not necessarily originate in t... more Evidence is presented that high-temperature superconductivity does not necessarily originate in the cuprate-planes. In the cuprates such as YBa2Cu3O7, i is argued that the superconductivity resides in the BaO layers. This superconductivity is s-wave, not d-wave, in the bulk. The trio of ruthenate compounds, Cu-doped Sr2YRuO6, GdSr2Cu2RuO8, and Gd2−zCezSr2Cu2RuO10 all super conduct in their SrO layers, which is why they have almost the same ∼45 K onset temperatures for superconductivity. Ba2GdRuO6, whether doped or not, does not superconduct, because the Gd breaks Cooper-like pairs. Bi2Sr2CaCu2O8 YBa2Cu3O7, Nd2−zCezCuO4 homologues, and the Pb2Sr2(RE)1−xCaxCu3O8 compounds that superconduct (where RE is a rare-earth) are all s-wave, p-type superconductors.

Physical review, Oct 1, 1986

Hyperfine Interactions, Dec 1, 1986

The interactions of muonium ( mu + e -, Mu) with the surfaces of fine silica powders have been ex... more The interactions of muonium ( mu + e -, Mu) with the surfaces of fine silica powders have been extensively studied using zero, longitudinal and transverse field muSR techniques. These studies indicate diffusion and trapping behavior of the Mu atoms on the silica surface, which is strongly influenced by the surface hydroxyl (OH) concentration. Specifically, the presence of the surface OH groups is observed to inhibit the surface mobility of the Mu atoms at low temperatures. Information provided by zero and longitudinal field data suggest a random anisotropic distortion of the Mu hyperfine interaction (RAHD) as the principal relaxation mechanism. A recently developed RAHD spin relaxation theory is used to interpret these data. Additional investigations, using platinum loaded silica, have yielded the first observed surface reaction of Mu. Studies of the interactions of positive muons with surfaces have been also extended to single crystals, where low energy (<10 eV) mu + and Mu - ions are observed to be reemitted from some materials (e.g., the surface of lithium fluoride). Future applications of these emission phenomena toward the development of a slow847-3 (or Mu-) beam are considered.

Physica C-superconductivity and Its Applications, Nov 1, 2000

Solid State Communications, May 1, 2001

Physical review, Aug 1, 1987

APS March Meeting Abstracts, Mar 1, 2002

ABSTRACT

Physica C-superconductivity and Its Applications, Aug 1, 2004

Muon spin rotation (μ + SR) data on a single-crystal of YBa 2 Cu 3 O 7 (T c 91.3 K, ΔT c < 0.5... more Muon spin rotation (μ + SR) data on a single-crystal of YBa 2 Cu 3 O 7 (T c 91.3 K, ΔT c < 0.5 K) are reported. After properly accounting for flux-pinning effects as functions of both field and temperature, we find the bulk ground state to be strong-coupled s-wave in character. The probability that YBa 2 Cu 3 O 7 is a bulk d-wave superconductor is less than 4×10 -6 .

Hyperfine Interactions, 1984

Journal of Superconductivity, Apr 1, 2004

The ruthenate compounds, Gd 2−z Ce z Sr 2 Cu 2 RuO 10 , GdSr 2 Cu 2 RuO 8 , and doped Sr 2 YRuO 6... more The ruthenate compounds, Gd 2−z Ce z Sr 2 Cu 2 RuO 10 , GdSr 2 Cu 2 RuO 8 , and doped Sr 2 YRuO 6 , all superconduct in their SrO layers, which is why they have almost the same ∼49 K onset temperatures for superconductivity. The sister compound Ba 2 GdRuO 6 , either doped or not, does not superconduct, because L = 0, J = 0 Gd breaks pairs and destroys superconductivity in the potentially superconducting BaO layers. High-temperature superconductivity resides in the SrO or BaO layers, or in interstitial-oxygen regions of the crystal, not in the cuprate-planes.

Physical review, May 1, 1993

Solid State Communications, Jul 1, 1985

Muon spin relaxation functions were measured in the magnetic superconductor Y9Co7 for T >~ 2.0K a... more Muon spin relaxation functions were measured in the magnetic superconductor Y9Co7 for T >~ 2.0K and at zero applied field. In the paramagnetic region (T >~ 6.0K) the depolarization of the muon spins is due to the s9 quasi-static Co nuclear moments. The onset of the magnetic state results in a fast-relaxing signal that corresponds to dipolar fields of the order of 1000e; this component grows steadily in amplitude as the material transists from the hybrid into the superconducting state. The data are consistent with the high degree of inhomogeneity of the (not long-range) ordering and coexisting but non-competing magnetic and superconducting properties in the "hybrid" state (2 < T< 5 K).

Physical Review Letters, Jun 30, 1986