M. B. Maple

University of California, San Diego, San Diego, California, United States

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Publications (830)1318.85 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have found that the erbium magnetic moment is so large that in ErRhâBâ it can relax muon polarization in times shorter than can be resolved by a typical ..mu..SR apparatus. The complete relaxation signal is resolved at temperatures above 50K only because of rapid fluctuation of the erbium moment, which partially decouples it from the muon's moment. Not much signal is resolved at temperatures less than or equal to 10K, but no dramatic effect is seen in crossing the superconducting transition temperature. The higher temperature local field fluctuation rates observed appear consistent with the exchange and spin-lattice fluctuation rates to be expected of erbium in this material. Perhaps more information on moment dynamics below 10K can be obtained by alloying erbium with a nonmagnetic rare earth such as yttrium within the RERhâBâ structure (as has been attempted for holmium), to reduce the rms local field at the muon.
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    ABSTRACT: We report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of ∼6.7-6.8 Å between Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya-Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4 f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order; however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.
    Journal of Physics Condensed Matter 07/2015; 27(31):315602. DOI:10.1088/0953-8984/27/31/315602 · 2.35 Impact Factor
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    ABSTRACT: We present data on the optical conductivity of URu$_{2-x}$(Fe,Os)$_{x}$Si$_{2}$. While the parent material URu$_2$Si$_2$ enters the enigmatic hidden order phase below 17.5 K, an antiferromagnetic phase is induced by the substitution of Fe or Os onto the Ru sites. We find that both the HO and the AFM phases exhibit an identical gap structure that is characterized by a loss of conductivity below the gap energy with spectral weight transferred to a narrow frequency region just above the gap, the typical optical signature of a density wave. The AFM phase is marked by strong increases in both transition temperature and the energy of the gap associated with the transition. In the normal phase just above the transition the optical scattering rate varies as $\omega^2$. We find that in both the HO and the AFM phases, our data are consistent with elastic resonant scattering of a Fermi liquid. This indicates that the appearance of a coherent state is a necessary condition for either ordered phase to emerge. Our measurements favor models in which the HO and the AFM phases are driven by the common physics of a nesting-induced density-wave-gap.
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    Y. Fang · D. Yazici · B. D. White · M. B. Maple
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    ABSTRACT: Electrical resistivity measurements on La$_{1-x}$Sm$_{x}$O$_{0.5}$F$_{0.5}$BiS$_{2}$ ($x$ = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature $T$$_{c}$ of each sample significantly increases at a Sm-concentration dependent pressure $P$$_{\rm t}$, indicating a pressure-induced phase transition from a low-$T$$_{c}$ to a high-$T$$_{c}$ phase. The compounds that have higher Sm concentrations have higher $T$$_{c}$ values at ambient pressure; however, the $T$$_{c}$ values at $P$ $>$ $P$$_{\rm t}$ decrease with $x$ and $P$$_{\rm t}$ shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed and metallic conduction is induced with increasing pressure in all of the samples. These results suggest that the pressure dependence of $T$$_{c}$ for the BiS$_{2}$-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of $T$$_{c}$ for SmO$_{0.5}$F$_{0.5}$BiS$_{2}$ under pressure.
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    ABSTRACT: The low temperature hidden order state of URu$_2$Si$_2$ has long been a subject of intense speculation, and is thought to represent an as yet undetermined many-body quantum state not realized by other known materials. Here, X-ray absorption spectroscopy (XAS) and high resolution resonant inelastic X-ray scattering (RIXS) are used to observe electronic excitation spectra of URu$_2$Si$_2$, as a means to identify the degrees of freedom available to constitute the hidden order wavefunction. Excitations are shown to have symmetries that derive from a correlated $5f^2$ atomic multiplet basis that is modified by itinerancy. The features, amplitude and temperature dependence of linear dichroism are in agreement with ground states that closely resemble the doublet $\Gamma_5$ crystal field state of uranium.
    Physical Review Letters 06/2015; 114(23). DOI:10.1103/PhysRevLett.114.236401 · 7.51 Impact Factor
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    ABSTRACT: We present electrical resistivity and ac-susceptibility measurements of GdTe$_3$, TbTe$_3$ and DyTe$_3$ performed under pressure. An upper charge-density-wave (CDW) is suppressed at a rate of $\mathrm{d}T_{\mathrm{CDW,1}}/\mathrm{d}P$ = $-$85 K/GPa. For TbTe$_3$ and DyTe$_3$, a second CDW below $T_{\mathrm{CDW,2}}$ increases with pressure until it reaches the $T_{\mathrm{CDW,1}}$($P$) line. For GdTe$_3$, the lower CDW emerges as pressure is increased above $\sim$ 1 GPa. As these two CDW states are suppressed with pressure, superconductivity (SC) appears in the three compounds at lower temperatures. Ac-susceptibility experiments performed on TbTe$_3$ provide compelling evidence for bulk SC in the low-pressure region of the phase diagram. We provide measurements of superconducting critical fields and discuss the origin of a high-pressure superconducting phase occurring above 5 GPa.
    Physical Review B 04/2015; 91(20). DOI:10.1103/PhysRevB.91.205114 · 3.74 Impact Factor
  • F Bridges · P Nast · J Wilde · T Keiber · M B Maple · K Huang · B D White
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    ABSTRACT: We investigated the local structure of the Sb doped skutterudite CePt4Ge12-x Sbx using the Extended X-ray Absorption Fine Structure Technique (EXAFS). As the concentration of Sb is increased the disorder around Ce increases rapidly, and for x = 3, the peak for the nearest neighbor (Ce-Ge) is no longer observed. In contrast, for the Pt site, the disorder of the nearest neighbors is small even for x = 3. Thus the distortions are anisotropic and appear to be mainly in the plane of the Ce-Ge bonds and Ge4 rings. The increased disorder about Ce will decrease the lattice thermal conductivity at low temperatures, and likely is part of the reason for improved thermoelectric properties for the x = 1 sample.
    IOP Conference Series Materials Science and Engineering 04/2015; 80(1). DOI:10.1088/1757-899X/80/1/012004
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    ABSTRACT: Experimental contributors to the field of Superconducting Materials share their informal views on the subject.
    Physica C Superconductivity 04/2015; 514. DOI:10.1016/j.physc.2015.03.003 · 1.11 Impact Factor
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    C.T. Wolowiec · B.D. White · M.B. Maple
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    ABSTRACT: We discuss several classes of conventional magnetic superconductors including the ternary rhodium borides and molybdenum chalcogenides (or Chevrel phases), and the quaternary nickel-borocarbides. These materials exhibit some exotic phenomena related to the interplay between superconductivity and long-range magnetic order including: the coexistence of superconductivity and antiferromagnetic order; reentrant and double reentrant superconductivity, magnetic field induced superconductivity, and the formation of a sinusoidally-modulated magnetic state that coexists with superconductivity. We introduce the article with a discussion of the binary and pseudobinary superconducting materials containing magnetic impurities which at best exhibit short-range “glassy” magnetic order. Early experiments on these materials led to the idea of a magnetic exchange interaction between the localized spins of magnetic impurity ions and the spins of the conduction electrons which plays an important role in understanding conventional magnetic superconductors. These advances provide a natural foundation for investigating unconventional superconductivity in heavy-fermion compounds, cuprates, and other classes of materials in which superconductivity coexists with, or is in proximity to, a magnetically-ordered phase.
    Physica C Superconductivity 04/2015; 514. DOI:10.1016/j.physc.2015.02.050 · 1.11 Impact Factor
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    ABSTRACT: Comprehensive investigations of superconductivity in the charge-doped high-temperature superconducting cuprates often involve examining the evolution of physical properties within a series of samples having controlled variations of some dopant element\char22{}most frequently oxygen. Many important observations have been extracted from such experiments, however, the associated measurements are by nature discrete snapshots of the evolving material. We demonstrate here a novel approach to sample preparation of the $\text{high-}{\mathit{\text{T}}}_{c}$ cuprate ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{x}$. By post-annealing a uniformly overdoped ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{x}(x$\approx${}7.0)$ film in a low pressure ${\text{O}}_{2}$ atmosphere with a thermal gradient across the film length, we have successfully grown a charge-gradient ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{$\nabla${}x}$ sample, i.e., a film having a varying oxygen doping level along the length of the substrate. Surprisingly, we observe three distinct regimes of oxygen distribution across the sample, as well as behavior pointing to a full alignment within the a-b plane.
    Physical Review B 04/2015; 91(14). DOI:10.1103/PhysRevB.91.144511 · 3.74 Impact Factor
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    Y P Singh · D J Haney · I K Lum · B D White · M B Maple · M Dzero · C C Almasan
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    ABSTRACT: Charge transport measurements under magnetic field and pressure on Ce 1- x Yb x CoIn 5 single crystalline alloys revealed that: (i) relatively small Yb substitution suppresses the field induced quantum critical point, with a complete suppression for Yb doping x > 0.07; (ii) the superconducting transition temperature ( T c ) and Kondo lattice coherence temperature ( T coh ) decrease with x , yet they remain finite over the wide range of Yb concentrations; (iii) both T c and T coh increase with pressure; (iv) there are two contributions to resistivity, which show different temperature and pressure dependences, implying that both heavy and light quasiparticles contribute to inelastic scattering. We also analyzed the pressure dependence of both T coh and T c within the composite pairing theory. In the purely static limit, we find that the composite pairing mechanism necessarily causes opposite behaviors of T coh and T c with pressure: if Tcoh grows with pressure, T c must decrease with pressure and vice versa.
    Journal of Physics Conference Series 03/2015; 592(1-1):012078. DOI:10.1088/1742-6596/592/1/012078
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    ABSTRACT: We report results of zero-field muon spin relaxation experiments on the filled-skutterudite superconductors~Pr$_{1-x}$Ce$_{x}$Pt$_4$Ge$_{12}$, $x = 0$, 0.07, 0.1, and 0.2, to investigate the effect of Ce doping on broken time-reversal symmetry (TRS) in the superconducting state. In these alloys broken TRS is signaled by the onset of a spontaneous static local magnetic field~$B_s$ below the superconducting transition temperature. We find that $B_s$ decreases linearly with $x$ and $\to 0$ at $x \approx 0.4$, close to the concentration above which superconductivity is no longer observed. The (Pr,Ce)Pt$_4$Ge$_{12}$ and isostructural (Pr,La)Os$_4$Sb$_{12}$ alloy series both exhibit superconductivity with broken TRS, and in both the decrease of $B_s$ is proportional to the decrease of Pr concentration. This suggests that Pr-Pr intersite interactions are responsible for the broken TRS\@. The two alloy series differ in that the La-doped alloys are superconducting for all La concentrations, suggesting that in (Pr,Ce)Pt$_4$Ge$_{12}$ pair-breaking by Ce doping suppresses superconductivity. For all $x$ the dynamic muon spin relaxation rate decreases somewhat in the superconducting state. This may be due to Korringa relaxation by conduction electrons, which is reduced by the opening of the superconducting energy gap.
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    ABSTRACT: We report results of zero-field muon spin relaxation experiments on the filled-skutterudite superconductors ${\mathrm{Pr}}_{1$-${}x}{\mathrm{Ce}}_{x}{\mathrm{Pt}}_{4}{\mathrm{Ge}}_{12},x=0$, 0.07, 0.1, and 0.2, to investigate the effect of Ce doping on broken time-reversal symmetry (TRS) in the superconducting state. In these alloys broken TRS is signaled by the onset of a spontaneous static local magnetic field ${B}_{s}$ below the superconducting transition temperature. We find that ${B}_{s}$ decreases linearly with $x$ and $$\rightarrow${}0$ at $x$\approx${}0.4$, close to the concentration above which superconductivity is no longer observed. The ${\text{(Pr,Ce)Pt}}_{4}{\mathrm{Ge}}_{12}$ and isostructural ${\text{(Pr,La)Os}}_{4}{\mathrm{Sb}}_{12}$ alloy series both exhibit superconductivity with broken TRS, and in both the decrease of ${B}_{s}$ is proportional to the decrease of Pr concentration. This suggests that Pr-Pr intersite interactions are responsible for the broken TRS. The two alloy series differ in that the La-doped alloys are superconducting for all La concentrations, suggesting that in ${\text{(Pr,Ce)Pt}}_{4}{\mathrm{Ge}}_{12}$ pair-breaking by Ce doping suppresses superconductivity. For all $x$ the dynamic muon spin relaxation rate decreases somewhat in the superconducting state. This may be due to Korringa relaxation by conduction electrons, which is reduced by the opening of the superconducting energy gap.
    Physical Review B 03/2015; 91(10). DOI:10.1103/PhysRevB.91.104523 · 3.74 Impact Factor
  • Y. Fang · D. Yazici · B. D. White · M. B. Maple
    Physical Review B 03/2015; 91(9). DOI:10.1103/PhysRevB.91.099903 · 3.74 Impact Factor
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    B.D. White · J.D. Thompson · M.B. Maple
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    ABSTRACT: Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion compounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates and iron-based superconductors. We conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.
    Physica C Superconductivity 02/2015; 514. DOI:10.1016/j.physc.2015.02.044 · 1.11 Impact Factor
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    ABSTRACT: La$_3$Co$_4$Sn$_{13}$ and La$_3$Ru$_4$Sn$_{13}$ were categorized as BCS superconductors. In a plot of the critical field $H_{c2}$ vs $T$, La$_3$Ru$_4$Sn$_{13}$ displays a second superconducting phase at the higher critical temperature $T_c^{\star}$, characteristic of inhomogeneous superconductors, while La$_3$Co$_4$Sn$_{13}$ shows bulk superconductivity below $T_c$. We observe a decrease in critical temperatures with external pressure and magnetic field for both compounds with $\frac{dT_c^{\star}}{dP} > \frac{dT_c}{dP}$. The pressure dependences of $T_c$ are interpreted according to the McMillan theory and understood to be a consequence of lattice stiffening. The investigation of the superconducting state of La$_3$Co$_x$Ru$_{4-x}$Sn$_{13}$ shows a $T_c^{\star}$ that is larger then $T_c$ for $x<4$. This unique and unexpected observation is discussed as a result of the local disorder and/or the effect of chemical pressure when Ru atoms are partially replaced by smaller Co atoms.
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    ABSTRACT: The local structure of two skutterudite families—CeM4As12 (M=Fe, Ru, Os) and LnCu3Ru4O12 (Ln=La, Pr, and Nd)—have been studied using the extended x-ray absorption fine structure (EXAFS) technique with a focus on the lattice vibrations about the rare-earth “rattler atoms” and the extent to which these vibrations can be considered local modes, with the rattler vibrating inside a nearly rigid cage. X-ray absorption data at all the metal edges were collected over a temperature range of 4 to 300 K and analyzed using standard procedures. The pair distances from EXAFS results agree quite well with the average structure obtained from diffraction. The cage structure is formed by the M and As atoms in CeM4As12 and by Cu, O, and Ru atoms in LnCu3Ru4O12. Although some of the bonds within the cage are quite stiff (correlated Debye temperatures, θcD, are ∼500 K for CeM4As12 and above 800 K for LnCu3Ru4O12), we show that the structure is not completely rigid. For the rattler atom the nearest-neighbor pairs have a relatively low Einstein temperature, θE:∼100–120 K for Ce-As and ∼130 K for Ln−O. Surprisingly, the behaviors of the second-neighbor pairs are quite different: for CeM4As12 the second-neighbor pairs (Ce−M) have a weaker bond while for LnCu3Ru4O12 the Ln−Ru second-neighbor pair has a stiffer effective spring constant than the first-neighbor pair. In addition, we show that the As4 or CuO4 rings are relatively rigid units and that their vibrations are anisotropic within these cubic structures, with stiff restoring forces perpendicular to the rings and much weaker restoring forces in directions parallel to the rings. Consequently vibrations of the rings may also act as “rattlers” and help suppress thermal conductivity. In general neither the rigid-cage approximation nor the simple reduced-mass approximation are sufficient for describing rattler behavior.
    Physical Review B 01/2015; 91(1). DOI:10.1103/PhysRevB.91.014109 · 3.74 Impact Factor
  • YP Singh · DJ Haney · XY Huang · BD White · MB Maple · M Dzero · CC Almasan
    Bulletin of the American Physical Society; 01/2015
  • B. D. White · K. Huang · M. B. Maple
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    ABSTRACT: Measurements of thermoelectric power $S(T)$ on the Kondo disorder system ${\mathrm{CePt}}_{4}{\mathrm{Ge}}_{12$-${}x}{\mathrm{Sb}}_{x}$ are remarkably sensitive to the distribution of Kondo temperatures $P({T}_{K})$, which develops out of a single Kondo temperature ${T}_{K}$ in ${\mathrm{CePt}}_{4}{\mathrm{Ge}}_{12}$ and is governed by the degree to which hybridization is disordered. Three distinct $S(T)$ behaviors are observed in concentration regions which coincide with the boundaries of Fermi-liquid, non-Fermi-liquid, and antiferromagnetically ordered ground states in this system. In the non-Fermi-liquid region, $S(T)/T$ diverges logarithmically with decreasing temperature over nearly one decade in the case of $x=0.84$.
    Physical Review B 12/2014; 90(23). DOI:10.1103/PhysRevB.90.235104 · 3.74 Impact Factor
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    ABSTRACT: Electrical resistivity, specific heat, and magnetization measurements on the URu [GRAPHICS] Os [GRAPHICS] Si [GRAPHICS] system suggest a phase transition from the 'hidden order' phase to another unidentified phase that is likely to be a large moment antiferromagnetic phase. It is noteworthy that the hidden order/large moment antiferromagnetic phase boundary [GRAPHICS] is enhanced from 17.5K at [GRAPHICS] = 0 to 50K at [GRAPHICS] = 1. However, as [GRAPHICS] increases, the gap opening in the Fermi surface due to the hidden order phase transition, deduced from electrical resistivity and specific heat measurements, decreases. This study reveals that both Fe and Os isoelectronic substitutions for Ru in URu [GRAPHICS] Si [GRAPHICS] yield an enhancement of [GRAPHICS] . In contrast to the URu [GRAPHICS] Fe [GRAPHICS] Si [GRAPHICS] system, where the unit cell volume decreases with [GRAPHICS] , in the URu [GRAPHICS] Os [GRAPHICS] Si [GRAPHICS] system, the unit cell volume increases with [GRAPHICS] . Thus the enhancement of the hidden order/large moment antiferromagnetic transition temperature cannot be solely due to an increase in chemical pressure.
    Philosophical Magazine 11/2014; 94(32-33):3681-3690. DOI:10.1080/14786435.2014.886022 · 1.43 Impact Factor

Publication Stats

12k Citations
1,318.85 Total Impact Points

Institutions

  • 1970–2014
    • University of California, San Diego
      • Department of Physics
      San Diego, California, United States
  • 2012
    • University of Silesia in Katowice
      • Institute of Physics
      Catowice, Silesian Voivodeship, Poland
    • University of Alabama at Birmingham
      • Department of Physics
      Birmingham, Alabama, United States
  • 2010
    • General Atomics
      San Diego, California, United States
  • 1979–2009
    • Applied Physical Sciences
      Groton, Connecticut, United States
  • 2006
    • Lawrence Livermore National Laboratory
      Livermore, California, United States
    • Chiba University
      • Department of Physics
      Tiba, Chiba, Japan
  • 2003
    • University of Campinas
      Conceição de Campinas, São Paulo, Brazil
  • 2002
    • Silesian University of Technology
      • Institute of Physics
      Gleiwitz, Silesian Voivodeship, Poland
  • 2000
    • Himeji Institute of Technology
      • Faculty of Science
      Himezi, Hyōgo, Japan
    • Universidad Nacional Autónoma de México
      Ciudad de México, Mexico City, Mexico
    • Kent State University
      • Department of Physics
      Кент, Ohio, United States
  • 1987–1995
    • Los Alamos National Laboratory
      • Materials Physics and Applications Division
      Лос-Аламос, California, United States
  • 1994
    • Whittier College
      Whittier, California, United States
    • Tufts University
      Бостон, Georgia, United States
  • 1991–1993
    • University of San Diego
      • Department of Physics
      San Diego, California, United States
  • 1990
    • The University of Texas at Austin
      • Department of Physics
      Texas City, TX, United States
    • CSU Mentor
      Long Beach, California, United States
    • Iowa State University
      • Ames Laboratory
      Ames, Iowa, United States
  • 1983
    • TRIUMF
      Vancouver, British Columbia, Canada
  • 1982
    • Palo Alto Research Center
      Palo Alto, California, United States
    • University of Kentucky
      • Department of Physics & Astronomy
      Lexington, Kentucky, United States
  • 1975
    • University of California, Berkeley
      • Department of Chemistry
      Berkeley, California, United States