About me


ZZ_jy18-053


Education
May 1986, University of British Columbia, Vancouver, BC
Ph.D. (Physics)
Thesis: The Interactions of Muonium with Silica Surfaces

June 1980, Western Washington University, Bellingham, WA
M.Sc. (Physics)

June 1978, Pacific Lutheran University, Tacoma, WA
B.Sc. (Physics)


Professional
Experience

Sep 2014 – Present, Department of Physics, College of William and Mary
Visiting Professor of Physics
Research – Principal Investigator

Aug 1999 – Jul 2014, Department of Physics, University of Notre Dame
Visiting (Aug 1999 – Aug 2004) / Adjunct (Aug 2004 – Aug 2014) Professor of Physics
Research – Principal Investigator

Sep 1999 – Aug 2011, Department of Physics, Arizona State University
Visiting (Sep 1999 – Aug 2002) / Adjunct (Sep 2002 – Aug 2011) Professor of Physics
Research – Principal Investigator

Feb 1997 – Present, Physikon Research Corporation
Vice President (Feb 1997 – Dec 2017) / President (Jan 2018 – Present)
Director of Research / President and CEO

May 1988 – Feb 1997, AT&T/Lucent Bell Laboratories, Murray Hill, NJ
Member of Technical Staff (MTS)
Research – Principal Investigator Read more

Mar 1986 – May 1988, AT&T Bell Laboratories, Murray Hill, NJ
Postdoctoral Fellow (Pre-Member of Technical Staff – PMTS)
Research

Jan 1986 – Mar 1986, Department of Physics, University of British Columbia
Postdoctoral Fellow
Research

Aug 1980 – Jan 1986, Department of Physics, University of British Columbia
Doctoral Candidate / Research Associate
Research / Teaching Assistant

Sep 1978 – Jun 1980, Department of Physics, Western Washington University
Masters Candidate
Teaching Assistant


Selected Research Highlights

  • Band-Gap Moderated Slow Positive Muon Beams – Dr. Harshman led the research group that discovered the first practical technique for producing a low-energy (<10 eV) positive muon beam.  It was given the acronym, μSOL (muon separator online).  The same 1986 paper reported the first observation of (< 10 eV) Mu (i.e., μ+ee) ions in vacuum.  In 1987, Harshman and co-workers increased the slow muon production rate by a factor of 100 using solid rare-gas moderators, producing a usable flux of slow muons. [Physical Review Letters 56, 2850 (1986)] [Physical Review B 36, 8850 (1987)]. The slow muon production technique developed by Harshman and coworkers was adopted by the Paul Sherrer Institut (PSI) for their slow positive muon beam facility (the μSR Yamazaki Prize for this work was awarded to PSI personnel who placed this technology on the end of a PSI surface muon channel).
  • Magnetic X-Ray Scattering in Holmium – By measuring the degree of linear polarization we identify the orbital and spin contributions to the x-ray magnetic scattering in holmium.  When the incident x-ray energy is tuned through the Lm absorption edge, we observe a fiftyfold resonant enhancement of the magnetic signal, and resonant integer harmonics.  The line shapes of the two linear components scattered parallel and perpendicular to the diffraction plane are distinct in energy with a 6-eV splitting. [Physical Review Letters 61, 1241 (1988)]. This paper was the experimental work cited for the 2003 Arthur H. Compton Award, presented to its first and fourth authors, along with two others not involved with this experiment (Dr. Harshman declined first-authorship because of other obligations at the time). In addition to taking part in all of the experiments, Dr. Harshman also designed, commissioned and supervised the building of the novel x-ray spectrometer necessary for its success.  During the experiment the acquisition computer failed; Dr. Harshman made the round trip from Cornell to Bell Labs to have it repaired.
  • High-Temperature Cuprate Superconductor Pairing State Symmetry – In 1987 using muon spin rotation (μ+SR) and measuring sintered powder samples of YBa2Cu3O7–δ, Harshman and coworkers provided the first measurements of the magnetic penetration and proof that the bulk pairing state of the superconducting hole condensate was nodeless, consistent with s-wave pairing and strong coupling [Physical Review B 36, 2386 (1987)].  Harshman and co-workers were also the first to measure the 60 K (oxygen-ordered) phase of YBa2Cu3O7–δ.  This research was followed by studies of heavily twinned single crystals of the same material, confirming the s-wave character and providing the first measurement of the mass anisotropy; mc ≥ 25 mab [Physical Review B 39, 851 (1989)].  In 1991, Harshman and co-workers presented μ+SR data on single-crystal Bi2Sr2CaCu2O8+δ showing a strongly temperature-dependent line shape, indicative of motional narrowing arising from fluxon depinning [Physical Review Letters 67, 3152 (1991)].  The fluxon lattice in earlier powder and heavily-twinned crystal samples of YBa2Cu3O7–δ was strongly pinned, suppressing fluxon depinning. However, by the mid 90’s, the quality of YBa2Cu3O7–δ crystals improved greatly, revealing a text-book example temperature-activated fluxon depinning.  Unfortunately, some researchers misinterpreted the extrinsic effects of fluxon depinning as being evidence of d-wave pairing.  To correct this misrepresentation, Harshman and co-workers conducted series of μ+SR experiments on a single-crystal of YBa2Cu3O7–δ, measuring the second moment of the frequency distribution, σ(T0,H), as a function of both temperature and applied field.  The strong (and non-monotonic) field dependence exhibited by σ(T→0,H),confirmed the presence of temperature-activated fluxon depinning.  By applying a self-consistent analysis approach, and accounting for the effects of fluxon depinning, Harshman and co-workers showed that the underlying gap function of the superconducting hole condensate was nodeless, and best described by the two-fluid model. [Physical Review B 69, 174505 (2004)] [Physical Review B, 72, 146502 (2005)].  In 2011, Harshman and Fiory extended this analysis technique to YBa2Cu4O8 and La2-xSrxCuO4 [Journal of Physics: Condensed Matter 23, 315702 (2011)].  This line of research has proven that the bulk high-TC pairing symmetry of the hole condensate in the cuprates is nodeless, consistent with s-wave and strong coupling, and has shown how fluxon motion can significantly affect the μ+SR data, even for single-crystal YBa2Cu3O7–δ, and how to account for it.
  • Oxygen Isotope Effect in High-TC Materials – For high-TC superconductors in which transition temperatures, TC, are reduced by doping, the oxygen isotope effect (OIE) coefficient in TC is shown to increase systematically with the pair-breaking rate and with the valence difference between the substituted and native ions.  Moreover, the OIE in Tc tends to zero as one approaches optimum (or ideal) stoichiometry at which the quality of the superconducting condensate is maximized.  In materials with isovalentsubstitutions, e.g., Sr for Ba or Zn for Cu in YBa2Cu3O7–δ, the small OIE of the parent (unsubstituted) compound is magnified, owing to pair-breaking disorder. In materials with heterovalent substitutions, e.g., La or Pr for Ba, where carrier densities are necessarily changed, pair-breaking induces a much larger OIE.  A seminal case is Pr-doped YBa2Cu3O7–δ, where data were previously misinterpreted, owing to the false assumption that Pr substitutes only for Y.  It is now clear, however, that the decrease in TC observed with Pr doping actually arises from pair-breaking caused by Pr-on-Ba-site defects introduced during crystal growth. When PrBa2Cu3O7–δ is grown correctly without such defects, TC remains unchanged (as in the case of most other rare earth substitutions for Y).  Invariance of TC under a 60% rare-earth mass increase provides strong evidence against phononic pairing mechanisms.  The fact that TC drops when Pr substitutes for Ba, but not for Y, indicates that the superconducting hole condensate resides in the BaO layers, where pair-breaking degrades TC and dramatically increases the OIE.  Superconductive pairing modeled on Coulomb coupling between the hole (BaO) and the electron (CuO2) layers is shown to resolve the serious shortcomings inherent in approaches based on electron-phonon interactions and is found to be generally applicable.  Moreover, the OIE in the magnetic penetration depth in alloys is shown to be constant, with degradation of TC up to 50%, and thus is unrelated to the OIE in TC. [Physical Review B 77, 024523 (2008)] [Physical Review B 80, 136502 (2009)]. This theoretical work corrects several earlier papers on the isotope effect in high-TC compounds, concludes non-phononic mediation and casts the isotope effect into isovalent and heterovalent substitutional categories.  Interpretations of differential OIE, combined with specific heat and thermal conductivity data indicate two interacting mobile carrier bands: one of holes and the other, electrons. 
  • Coexistence of Holes and Electrons in High-TC Compounds – Normal state resistivity and Hall effect are shown to be successfully modeled by a two-band model of holes and electrons that is applied self-consistently to (i) DC transport data reported for eight bulk-crystal and six oriented-film specimens of YBa2Cu3O7–δ, and (ii) far-infrared Hall angle data reported for YBa2Cu3O7–δ and Bi2Sr2CaCu2O8+δ.  The electron band exhibits extremely strong scattering; the extrapolated DC residual resistivity of the electronic component is shown to be consistent with the previously observed excess thermal conductivity and excess electrodynamic conductivity at low temperature.  Two-band hole-electron analysis of Hall angle data suggest that the electrons possess the greater effective mass. [Philosophical Magazine 91, 818 (2011)] [arXiv]. Theoretical analysis of Hall effect data in high-TC compounds showing the presence of two distinct carrier types of opposite sign.  By applying a two-band model to the data from several DC and AC transport measurements, Dr. Harshman and co-workers were able to prove that mobile electrons coexist with the holes in the high-TC compounds.  The electrons were found to be heavier that the holes, possess 3D mobility (while the hole were generally confined to two dimensions) and exhibit strong scattering.  This discovery suggested that the heavier electrons may play a role in mediating the pairing of lighter holes.
  • Theory of High-TC Superconductivity: Transition Temperature – It is demonstrated that the transition temperature (TC) of high-TC superconductors is determined by their layered crystal structure, bond lengths, valency properties of the ions, and Coulomb coupling between electronic bands in adjacent, spatially separated layers.  Analysis of 31 high-Tc materials (cuprates, ruthenates, rutheno-cuprates, iron pnictides, organics) yields the universal relationship for optimal compounds, kBTC0 = β/ℓζ, where ℓ is related to the mean spacing between interacting charges in the layers, ζ is the distance between interacting electronic layers, β is a universal constant and TC0 is the optimal transition temperature (determined to within an uncertainty of ± 1.4 K by this relationship).  Non-optimum compounds, in which sample degradation is evident, e.g. by broadened superconducting transitions and diminished Meissner fractions, typically exhibit reduced T< TC0.  It is shown that TC0 may be obtained from an average of Coulomb interaction forces between the two layers. [Journal of Physics: Condensed Matter. 23, 295701 (2011)] [arXiv] [News Article] [Corrigendum: J. Phys.: Condens. Matter 23 349501 (2011)].  Also listed in J. Phys.: Condens. MatterHighlights of 2011. Seminal work on a theoretical model for high-TC0 pairing based on Coulomb interactions between two nearest-neighbor charge layers.  The fact that the universal constant β is equal to about twice the reduced electron Compton wavelength, and the equation for TC0 in independent of band mass, suggests a central role for Compton scatting in high-TC superconductivity, where pairing is accomplished via virtual photons.
  • Expansion of the High-TC Interlayer/Interfacial Pairing Theory – Subsequent to the publication of the seminal work in 2011 (above), the interlayer Coulomb pairing model is shown to apply to other superconductor families; iron calcogenides [Journal of Physics: Condensed Matter 24, 135701 (2012)], the intercalated group-4-metal nitride halides [Physical Review B 90, 186501 (2014)] [Journal of Superconductivity and Novel Magnetism 28, 2967 (2015)] and  (CaxLa1–x)(Ba1.75–xLa0.25+x)Cu3Oy (i.e., CLBLCO) [Physical Review B 86, 144533 (2012)]. For the charged compensated  CLBLCO compound, the first accurate calculation of TC for the related non-optimal materials is provided.  Two Tl-based cuprates of the form Tl1–x(Ba/Sr/La)2CaO5–δ [Journal of Physics and Chemistry of Solids 85, 106 (2015)] are also added to the growing list of compounds for which TC is accurately calculated; a derivation of σ is introduced for the optimal Tl2Ba2Caη–1CuηO2η+2 (for η = 1, 2, 3) compounds, which exhibit a Tl oxidation state at or near +3, obtaining the fundamental value σ0 = 0.228 previously established for YBa2Cu3O6.92. Also reported is the marked enhancement in σ associated with Tl+1 and analogous inner-layer cations relative to higher-valence cations. For a model proposition of σ = σ0, the fractional Tl+1 content of the mixed-valence compound, TlBa2Ca2Cu3O9±δ, is predicted to be 1/3 at optimization, in agreement with existing data.  This work has unequivocally established the nature of the high-TC pairing mechanism to be Coulombic, requiring interaction between two physically separated charge reservoirs. The theory is the only published predictive model for TC in the high-TC field.
  • Application of Coulomb Interlayer/Interfacial Pairing Theory to 3D Compounds – The applicability of the interfacial Coulombic pairing mechanism has been extended to the 3D macromolecular A3C60 superconducting family of compounds [Journal of Physics: Condensed Matter 29, 145602 (2017)] accurately predicts the optimal transition temperatures in A15 and fcc Cs3C60.  Based upon the differing disorder between H3S and D3S [Superconductor Science and Technology 30, 045011 (2017)], the H-D isotope effect exponent is accurately determined in cubic H3S, thereby setting significant limits on the electron-phonon coupling strength and opening the door to unconventional superconductivity.  Subsequent application of the Coulomb interfacial mediation model to H3S gives TC0 = 198.5 ± 3.0 K is in excellent agreement with transition temperatures determined from resistivity (196 – 200 K onsets, 190 – 197 K midpoints), susceptibility (200 K onset), and critical magnetic fields (203.5 K by extrapolation).  Analysis of mid-infrared reflectivity data also confirms the expected correlation between boson energy and ζ–1 [Journal of Physics: Condensed Matter 29, 445702 (2017)].  These results confirm that Coulombic mediation specifically requires physically separated charge reservoirs and is not determined by structural dimensionality.

Journal Publications (chronological order)Read more


Conference PublicationsRead more


Invited TalksRead more


AbstractsRead more


Work included in Magazine Articles, Journal Highlights and Editorials

Other Activities

Government Review Panels

  • Served on Department of Energy Peer Review Panel, Arlington, VA, 28-30 July 1992.
  • Served on Department of Energy Peer Review Panel, Arlington, VA, 1-3 September 1992.

Patents & Copyrights

Radioactive Ion (Implantation), J. Vincent, T. Ruth, A. Zyuzin, J. D’Auria, D. Ottewell and  D. R. Harshman (TRIUMF Patent – application for arterial stents).  Priority date for all applications: 12 Dec. 2001.

Country/Entity

World / WIPO
European Union
European Union
European Union
Canada
Mexico
France
Germany
United Kingdom
Japan
Korea
United States

Publ. No.

WO 03/053509
EP 1 946 796 A2
EP 1 946 797 A2
1463533
N/A
WO 03/053509
N/A
N/A
N/A
2005-513451
N/A
US 2005/0118098 A1

Application No.

PCT/US02/39557
07150325.4
07150329.6
02787004.7
CA 2,470,006
PA/a/2004/005655
02787004.7
02787004.7
02787004.7
2003-554265
10-2004-7008719
10/498,368

Filing Date

12 Dec. 2002
21 Dec. 2007
21 Dec. 2007
9 Jul. 2004
10 Jun. 2004
11 Jun. 2004
12 Dec. 2002
12 Dec. 2002
12 Dec. 2002
11 May 2004
5 Jun. 2004
14 Jan. 2005

These patents were allowed to lapse in 2010.

Layered Ionic Superconductor, D. R. Harshman and A. T. Fiory

Country/Entity

United States

Patent ID

US 8,703,651 B2

Application No.

13/543,655

Filing Date

6 Jul. 2012


Copyrighted Verse

Voices (Registration No. PAu 2-167-731, 24 February 1997)
False Winds of Hope (Registration No. PAu 2-095-422, 14 June 1996)
Faraday Hollander (Registration No. Registration No. TXu 232 915, 20 March 1986)


Professional memberships


References
Dr. Anthony T. Fiory, Research Scientist in Physics
New Jersey Institute of Technology, Newark, New Jersey 07102
fiory@alum.mit.edu

Dr. William J. Kossler, Professor (Emeritus) of Physics
The College of William and Mary, Williamsburg, Virginia 23185
wjkoss@wm.edu

Dr. Peter B. Littlewood, Director
Argonne National Laboratory, Argonne, IL 60439
Professor of Physics, James Franck Institute
University of Chicago, Chicago, Illinois 76063
pblittlewood@anl.gov

Dr. James L. Smith, Chief Scientist & Fellow (Emeritus)
Los Alamos National Laboratory
Materials Technology: Metallurgy – MST-6
Los Alamos, New Mexico 87545
jlsmith@lanl.gov


Personal
Birth Date: 13 August 1956 | Honolulu, Hawaii


Interests and activities
Robotics, Biking, Poetry, Drums, Fishing, Camping


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