About

Richard Greene is known for his many years of productive research on the physics of novel superconducting materials, at the IBM research laboratories and at the University of Maryland. He and his collaborators discovered the first known polymeric and two-dimensional organic superconductors in the 1970s. Since 1986, Dr. Greene has done extensive research on high-Tc superconductors, primarily electron-doped cuprates and iron-based materials. He has written several well-known reviews about these two superconducting systems. He was also involved in the development of the relaxation technique for specific heat measurements, a technique that is now widely used in the Quantum Design PPMS. His publications are very highly cited, with over 33,000 citations and an h-index of 96. He was the founding director of the Center for Superconductivity Research at the University of Maryland in 1989. He is a Fellow of the APS and the AAAS and the APS Dissertation Award for Experimental Condensed Matter Physics is named in his honor. In 2022, he was named a University of Maryland Distinguished University Professor.

Research topics

• Quantum mechanics
• Physics
• Condensed matter physics

Selected publications

• Evidence for spin-fluctuation-mediated superconductivity in electron-doped cuprates

  ArXiv.org · 2025-02-19

  preprintOpen access

  In conventional, phonon-mediated superconductors, the transition temperature $T_c$ and normal-state scattering rate $1/τ$ - deduced from the linear-in-temperature resistivity $ρ(T)$ - are linked through the electron-phonon coupling strength $λ_{\rm ph}$. In cuprate high-$T_c$ superconductors, no equivalent $λ$ has yet been identified, despite the fact that at high doping, $α$ - the low-$T$ $T$-linear coefficient of $ρ(T)$ - also scales with $T_c$. Here, we use dc resistivity and high-field magnetoresistance to extract $τ^{-1}$ in electron-doped La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) as a function of $x$ from optimal doping to beyond the superconducting dome. A highly anisotropic inelastic component to $τ^{-1}$ is revealed whose magnitude diminishes markedly across the doping series. Using known Fermi surface parameters and subsequent modelling of the Hall coefficient, we demonstrate that the form of $τ^{-1}$ in LCCO is consistent with scattering off commensurate antiferromagnetic spin fluctuations of variable strength $λ_{\rm sf}$. The clear correlation between $α$, $λ_{\rm sf}$ and $T_c$ then identifies low-energy spin-fluctuations as the primary pairing glue in electron-doped cuprates. The contrasting magnetotransport behaviour in hole-doped cuprates suggests that the higher $T_c$ in the latter cannot be attributed solely to an increase in $λ_{\rm sf}$. Indeed, the success in modelling LCCO serves to reinforces the notion that resolving the origin of high-temperature superconductivity in hole-doped cuprates may require more than a simple extension of BCS theory.

  PublisherOA PDFDOI

• Dissecting coupled orders in a terahertz-driven electron-doped cuprate

  ArXiv.org · 2025-04-16

  preprintOpen access

  The interplay between superconductivity and charge density wave has often been studied from an equilibrium point of view. For example, using static tuning knobs such as doping, magnetic field and pressure, superconductivity can be enhanced or suppressed. The resulting effect on the co-existing charge density wave order, if any, is judged by variations in its ground state properties such as the ordering temperature or the spatial correlation. Such an approach can be understood as coordinated static displacements of two coupled order parameters within a Ginzburg-Landau description, evincing their interplay as either co-operative or competing but does not provide further microscopic information about the interaction. In order to assess such information, we dynamically perturb both orders from equilibrium and observe their coupling directly in the time-domain. We show that high-field multicycle terahertz pulses drive both the Higgs amplitude fluctuations of the superconducting order as well as collective fluctuations of the charge order in an electron-doped cuprate, resulting in characteristic third harmonic generation. A notable time delay is manifested between their respective driven dynamics. We propose that this may signify the important energy scale describing their coupling or imply a terahertz field-depinned charge density wave that destroys macroscopic superconductivity. Our work demonstrates a holistic approach for investigating coupled superconducting and charge density wave orders, which may shed novel light on their intertwined presence and widespread fluctuations in many classes of unconventional superconductors.

  PublisherOA PDFDOI

• Superconducting phase diagram in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Bi</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mi>Ni</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>–</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> thin films: The effects of Bi stoichiometry on superconductivity

  Physical Review Materials · 2024-07-25 · 1 citations

  articleOpen access

  The Bi-Ni binary system has been of interest due to possible unconventional superconductivity aroused therein, such as time-reversal symmetry breaking in Bi/Ni bilayers or the coexistence of superconductivity and ferromagnetism in ${\mathrm{Bi}}_{3}\mathrm{Ni}$ crystals. While Ni acts as a ferromagnetic element in such systems, the role of the strong spin-orbit coupling element Bi in superconductivity has remained unexplored. In this work, we systematically studied the effects of Bi stoichiometry on the superconductivity of ${\mathrm{Bi}}_{x}{\mathrm{Ni}}_{1--x}$ thin films ($x\ensuremath{\approx}0.5--0.9$) fabricated via a composition-spread approach. The superconducting phase map of ${\mathrm{Bi}}_{x}{\mathrm{Ni}}_{1--x}$ thin films exhibited a superconducting composition region attributable to the intermetallic ${\mathrm{Bi}}_{3}\mathrm{Ni}$ phase with different amounts of excess Bi, revealed by synchrotron x-ray diffraction analysis. Interestingly, the mixed-phase region with ${\mathrm{Bi}}_{3}\mathrm{Ni}$ and Bi showed unusual increases in the superconducting transition temperature and residual resistance ratio as more Bi impurities were included, with the maximum ${T}_{\mathrm{c}}$ ($=4.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$) observed at $x\ensuremath{\approx}0.79$. A correlation analysis of structural, electrical, and magneto-transport characteristics across the composition variation revealed that the unusual superconducting ``dome'' is due to two competing roles of Bi: impurity scattering and carrier doping. We found that the carrier doping effect is dominant in the mild doping regime $(0.74\ensuremath{\le}x\ensuremath{\le}0.79)$, while impurity scattering becomes more pronounced at larger Bi stoichiometry.

  PublisherOA PDFDOI

• The Strange Metal State of the high-Tc Cuprates

  arXiv (Cornell University) · 2023-06-26

  preprintOpen access1st authorCorresponding

  This paper is dedicated to the memory of Professor K. Alex Müller. I present a few remarks about my interactions with Alex over the years. Then I present a very brief summary of recent transport studies of the strange metal normal-state in the high-temperature copper oxide superconductors, a subject of great interest to Alex.

  PublisherOA PDFDOI

• The strange metal state of the high-Tc cuprates

  Physica C Superconductivity · 2023-07-20 · 4 citations

  article1st authorCorresponding
  PublisherDOI

• MuleSoft MCIA-Level-1 Dumps - Pass With Real MCIA-Level-1 Exam Questions

  Zenodo (CERN European Organization for Nuclear Research) · 2022-01-11

  articleOpen access1st authorCorresponding

  100% actual MuleSoft MCIA-Level-1 dumps from ExamsLead. Our MCIA-Level-1 exam questions are verified by highly experienced MuleSoft experts.\n\nProficient Learning Material For MuleSoft MCIA-Level-1 Exam Success\n\nMuleSoft certifications are the most famous certifications in the world of information technology. MCIA-Level-1 exam is one of the exams that help you to become a MuleSoft Certified professional if you pass it with good result. There are many IT professionals who want to take the MuleSoft MCIA-Level-1 MuleSoft Certified Integration Architect - Level 1 Exam and get a successful professional career. But the competition in the IT industry has made it difficult to pass the MCIA-Level-1 exam in the first attempt. There are very few candidates who make it get through the MCIA-Level-1 exam in their first attempt. The most important thing to pass the MuleSoft MCIA-Level-1 exam is to understand it properly and for this purpose, you need a proficient learning material such as ExamsLead.\n\nMuleSoft MCIA-Level-1 Dumps In PDF Format\n\nExamsLead offers the MCIA-Level-1 test dumps come in the PDF format that is easy to use and understand for you. The MCIA-Level-1 pdf dumps helps you to learn and practice for the MuleSoft MCIA-Level-1 exam without any disturbance.\n\nReal &amp; Valid MuleSoft MCIA-Level-1 Dumps PDF\n\nExamsLead offers the questions and answers for the preparation of MuleSoft MCIA-Level-1 MuleSoft Certified Integration Architect - Level 1 Exam. All the questions and answers belong to the real and latest MuleSoft Certified Integration Architect - Level 1 Exam MCIA-Level-1 exam and are 100% accurate. If you prepare all of these questions and answers then you will be able to pass the MCIA-Level-1 exam with exceptional results.\n\nMuleSoft MCIA-Level-1 Dumps Prepared By MuleSoft Experts\n\nExamsLead has experts who know the requirements to pass the MuleSoft MCIA-Level-1 exam. They prepare the learning material for the preparation of MuleSoft Certified Integration Architect - Level 1 Exam MCIA-Level-1 exam according to the latest and actual syllabus of the MuleSoft Certified Integration Architect - Level 1 Exam MCIA-Level-1 exam.\n\nTry Free MCIA-Level-1 Dumps Demo Exam Q&amp;A - https://examslead.com/mcia-level-1-practice-exam-dumps/

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• Thermal Hall conductivity of electron-doped cuprates

  Physical review. B./Physical review. B · 2022 · 21 citations

  • Condensed matter physics
  • Physics
  • Quantum mechanics

  Measurements of the thermal Hall conductivity in hole-doped cuprates have shown that phonons acquire chirality in a magnetic field both in the pseudogap phase and in the Mott insulator state. The microscopic mechanism at play is still unclear. A number of theoretical proposals are being considered including skew scattering of phonons by various defects, the coupling of phonons to spins, and a state of loop-current order with the appropriate symmetries, but more experimental information is required to constrain theoretical scenarios. Here we present our study of the thermal Hall conductivity ${\ensuremath{\kappa}}_{\mathrm{xy}}$ in the electron-doped cuprates ${\mathrm{Nd}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ and ${\mathrm{Pr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ for dopings across the phase diagram, from $x=0$ in the insulating antiferromagnetic phase up to $x=0.17$ in the metallic phase above optimal doping. We observe a large negative thermal Hall conductivity at all dopings in both materials. Since heat conduction perpendicular to the ${\mathrm{CuO}}_{2}$ planes is dominated by phonons, the large thermal Hall conductivity we observe in electron-doped cuprates for a heat current in that direction must also be due to phonons, as in hole-doped cuprates. However, the degree of chirality, measured as the ratio $|{\ensuremath{\kappa}}_{\mathrm{xy}}/{\ensuremath{\kappa}}_{\mathrm{xx}}|$ where ${\ensuremath{\kappa}}_{\mathrm{xx}}$ is the longitudinal thermal conductivity, is much larger in the electron-doped cuprates. We discuss various factors that may be involved in the mechanism that confers chirality to phonons in cuprates, including short-range spin correlations.

  PublisherOA PDFDOI

• Hidden strange metallic state in underdoped electron-doped cuprates

  Physical review. B./Physical review. B · 2021-06-01 · 6 citations

  articleOpen accessSenior author

  The low-temperature linear-in-T resistivity of ``strange metals,'' such as the metallic state of the cuprate high-temperature superconductors, has long been thought to be associated with a quantum critical point. However, recent transport studies of the cuprates have found this behavior persists over a finite range of overdoping. In this work, we report magnetoresistance and Hall effect results for electron-doped films of the cuprate superconductor ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ (LCCO) for temperatures from 0.7 to 45 K and magnetic fields up to 65 T. For $x=0.12$ and 0.13, just below the Fermi surface reconstruction (FSR) at $x=0.14$, the normal state in-plane resistivity exhibits a well-known upturn at low temperature. Our new results show that this resistivity upturn is eliminated at high magnetic field and the resistivity becomes linear-in-temperature from \ensuremath{\sim}40 K down to 0.7 K. The magnitude of the linear coefficient scales with Tc and doping, as found previously [K. Jin, Nature(London) 476, 73 (2011), T. Sarkar, Sci. Adv. 5, eaav6753 (2019)] for dopings above the FSR. This striking observation suggests that the strange metal is not confined to a single ``critical point'' in the phase diagram, but rather is a robust universal feature of the metallic ground state of the cuprates.

  PublisherDOI

• BCS <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>d</mml:mi></mml:mrow></mml:math>-wave behavior in the terahertz electrodynamic response of electron-doped cuprate superconductors

  Physical review. B./Physical review. B · 2021-08-02 · 12 citations

  articleOpen access

  Although cuprate superconductors have been intensively studied for the past decades, there is no consensus regarding the microscopic origin of their superconductivity. In this paper, we measure the low-energy electrodynamic response of slightly underdoped and overdoped ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ thin films using time-domain terahertz (THz) spectroscopy to determine the temperature and field dependence of the superfluid spectral weight. We show that the temperature dependence obeys the relation ${\mathrm{n}}_{s}$ $\ensuremath{\propto}\phantom{\rule{4pt}{0ex}}1\ensuremath{-}{(T/{T}_{c})}^{2}$, typical for dirty limit BCS-like $d$-wave superconductors. Furthermore, the magnetic field dependence was found to follow a sublinear $\sqrt{B}$ form, which supports predictions based on a $d$-wave symmetry for the superconducting gap. These observations imply that the superconducting order in these electron-doped cuprates can be well described in terms of a disordered BCS $d$-wave formalism.

  PublisherOA PDFDOI

• Counterexample to the conjectured Planckian bound on transport

  Physical review. B./Physical review. B · 2021-12-20 · 1 citations

  preprintOpen accessSenior author

  It has recently been conjectured that the transport relaxation rate in metals is bounded above by the temperature of the system. In this paper, we discuss the transport phenomenology of overdoped electron-doped cuprates, which we show constitute an unambiguous counterexample to this putative ``Planckian'' bound, raising serious questions about the efficacy of the bound.

  PublisherOA PDFDOI

Recent grants

• Emergent Quantum Phenomena in Topological Kondo Insulators

  NSF · $420k · 2014–2018

• Investigation of the Low Temperature Normal State of Electron-Doped Copper Oxides

  NSF · $375k · 2004–2007

• Investigation of the strange metal normal state of electron-doped oxide superconductors

  NSF · $480k · 2020–2024

• Electronic Properties of Electron-Doped Oxide Superconductors.

  NSF · $415k · 2007–2011

• A study of unconventional transport in electron-doped oxide superconductors

  NSF · $450k · 2017–2020

Frequent coauthors

• T. Venkatesan

  University of Oklahoma

  72 shared

• P. Fournier

  55 shared

• Ichiro Takeuchi

  University of Maryland, College Park

  37 shared

• J. S. Higgins

  University of Pittsburgh

  36 shared

• Amlan Biswas

  31 shared

• V. N. Smolyaninova

  30 shared

• Johnpierre Paglione

  28 shared

• J. L. Peng

  26 shared

Labs

• Greene, Richard - UMD PhysicsPI

Awards & honors

• APS Fellow
• AAAS Fellow
• APS Dissertation Award for Experimental Condensed Matter Phy…
• Kamerlingh Onnes Prize Winner
• University of Maryland Distinguished University Professor