Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Q48: Superconductivity: Material and Properties |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Martin Nikolo, St. Louis University Room: Mile High Ballroom 1A-1B |
Wednesday, March 5, 2014 2:30PM - 2:42PM |
Q48.00001: Unexpected Giant Superconducting Fluctuation and Anomalous Semiconducting Normal State in NdO$_{\mathrm{1-x}}$F$_{\mathrm{x}}$Bi$_{\mathrm{1-y}}$S$_{2}$ Single Crystals Xiyu Zhu, Jianzhong Liu, Delong Fang, Zhenyu Wang, Jie Xing, Zengyi Du, Huan Yang, Hai-Hu Wen Experiments on single crystals of BiS$_{\mathrm{2}}$-based superconductors are highly desired. We report the successful growth of the NdO$_{\mathrm{1-x}}$F$_{\mathrm{x}}$Bi$_{\mathrm{1-y}}$S$_{\mathrm{2}}$ single crystals. Resistive and magnetic measurements reveal that the bulk superconducting transition occurs at Tc $=$ 4.83 K, while an unexpected giant superconducting fluctuation appears at temperatures as high as 2-4 kBTC. Analysis based on the anisotropic Ginzbaug-Landau theory gives an anisotropy $\gamma = \sqrt {m_{c} /m_{ab} } \approx 30\sim 45$. Two gap features with magnitudes of about 3.5 $\pm$ 0.3meV and 7.5 $\pm$ 1 meV were observed by scanning tunneling spectroscopy. The smaller gap is associated with the bulk superconducting transition yielding a huge ratio $2\Delta_{s}^{1} /k_{B} T_{c} =$16.8, the larger gap remains up to about 26 K. The normal state recovered by applying a high magnetic field shows an anomalous semiconducting behavior. All these suggest that the superconductivity in this newly discovered superconductor cannot be formatted into the BCS picture. [Preview Abstract] |
Wednesday, March 5, 2014 2:42PM - 2:54PM |
Q48.00002: Superconductivity in the Zintl intermetallic compound Ca$_{11}$Bi$_{10-x}$ Mihai Sturza, Han Fei, Christos Malliakas, Helmut Claus, Duck Young Chung, Mercouri Kanatzidis The recent discovery of the iron-based superconductors with unconventional superconductivity as a new class of superconductors has attracted great attention and triggered extensive research for new compounds. We report the new superconductor Ca$_{11}$Bi$_{10-x}$, which is in fact a Zintl phase. The structure of Ca$_{11}$Bi$_{10}$ contains three discrete anionic fragments: isolated Bi$^{3-}$ ions, dumbbells of Bi$_{2}^{4-}$ and square planar rings of Bi$_{4}^{4-}$ surrounded by Ca$^{2+}$cations. The Bi$_{4}^{4-}$ squares and the Bi$_{2}^{4-}$ dumbbells interact with one another through Bi---Bi bonding to form an extended 3D framework. The extended three-dimensional Bi-Bi interactions are responsible for the metallic behavior observed above T$_{c}$. Electronic band structure calculations at the density functional theory (DFT) level confirm the metallic character of the material. Defects in the form of vacancies on the Bi-sites were also found using single crystal X-ray analysis. The unexpected finding is that unlike most superconductors Ca$_{11}$Bi$_{10-x}$ has very low carrier density. The Ca$_{11}$Bi$_{10-x}$ system is the first member of the intermetallic class M$_{11}$X$_{10}$ (M$=$Ca, Sr, Ba; X$=$Bi, Sb) that exhibits superconductivity suggesting that a broader family of Bi or Sb-containing superconductors may exist. [Preview Abstract] |
Wednesday, March 5, 2014 2:54PM - 3:06PM |
Q48.00003: Spin-orbit effects on electronic transport in superconductor/normal metal heterostructures Nayana Shah, Kuei Sun Electronic transport in superconductor/normal metal (S/N) heterostructures has been extensively investigated for understanding its coherent nature and application on probing quantum entanglement. Recent works have focused on a semiconductor nanowire with a proximity-induced superconducting gap on its part, which makes such device an effective S/N heterostructure with the presence of spin-orbit couplings (SOC) due to the material properties. The SOC splits the energy spectrum in a momentum-dependent pseudo-spin space and thus plays an essential role on the system's Fermi points as well as the group velocities of propagating particles and holes. We study the effects of Rashba and Dresselhaus SOCs and their interplay with the interfacial barriers on various transport processes, including normal/Andreev reflections on the N side and quasi-particle/hole transmissions on the S side. We obtain analytic results for the small SOC regime and numerically calculate experimental observables such as an I/V curve in a wide parameter space. Our results ought to advance the current study on such systems, especially that exploring Majorana zero modes on superconducting nanowires or spin transport in helical liquids. [Preview Abstract] |
Wednesday, March 5, 2014 3:06PM - 3:18PM |
Q48.00004: Nature of local distortions in newly-discovered disordered superconductor, LaO$_{\mathrm{1-x}}$F$_{\mathrm{x}}$BiS$_{2}$ Anushika Athauda, Bing Li, Shinichiro Yano, Seunghun Lee, Despina Louca, Yoshikazu Mizuguchi LaO$_{\mathrm{1-x}}$F$_{\mathrm{x}}$BiS$_{2}$ is a disordered, non-magnetic superconductor belonging to the novel family of BiS$_{2}$ layered superconductors. The parent phase, LaOBiS$_{2}$, is a band insulator with tetragonal structure (P4/nmm space group). The highest T$_{\mathrm{c}}$ of LaO$_{\mathrm{1-x}}$F$_{\mathrm{x}}$BiS$_{2}$ is attained at x $=$ 0.5, as 10.8 K. Upon F doping or temperature change, little change had been reported in the low-energy portion of the phonon spectrum and the question whether LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ is a BCS superconductor or not remains unsolved. The local atomic structures of LaOBiS$_{2}$ and LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ were investigated as a function of temperature by using elastic neutron scattering and the pair density function analysis from 6 to 300 K and 2 to 300K respectively. We present possible models of local structure of LaOBiS$_{2}$ and LaO$_{0.5}$F$_{0.5}$BiS$_{2}$ which qualitatively explain the temperature dependence and composition dependence. [Preview Abstract] |
Wednesday, March 5, 2014 3:18PM - 3:30PM |
Q48.00005: Coexistence of ferromagnetism and superconductivity in CeO0.3F0.7BiS2 Jooseop Lee Neutron scattering measurements have been performed on a polycrystalline sample of the newly discovered layered superconductor CeO0.3F0.7BiS2 with or without a magnetic field. This system exhibits the rare and interesting case of the coexistence of ferromagnetism and superconductivity, which is hardly realized in the conventional phonon mediated superconductors due to their antagonistic nature. The crystal and magnetic structures was investigated together with the spin fluctuations, and the spin Hamiltonian describing the spin dynamics in this system was determined. In addition, we examined the external magnetic field dependence of both magnetic structure and its excitation. It seems that superconductivity is robust against a magnetic field and there is no direct relationship between magnetism and superconductivity in this system. [Preview Abstract] |
Wednesday, March 5, 2014 3:30PM - 3:42PM |
Q48.00006: Hole Doped SrPt3P - Physical Characterization and Analysis BenMaan Jawdat, Bing Lv, Yuyi Xue, Ching-wu Chu In 2012, Takayama et al. [1] reported superconductivity up to 8.4 K in APt$_3$P (A = Sr, Ca, and La). Its crystal structure is similar to that of the noncentrosymmetric superconductor CePt$_3$Si, although it possesses a center of inversion symmetry. Afterwards, Nekrasov et al. predicted in a theoretical work that hole doping the system would increase N($\epsilon_f$) as well as the $\mathrm{T_C}$ [2]. We have therefore decided to investigate Si-doped SrPt$_3$P resistively, magnetically and calorimetrically. We found that 1. the partial replacement of P by Si results in hole-doping evidenced from our Hall measurements, within the solubility of Si in SrPt$_3$P, 2. The Sommerfeld coefficient of the compounds increases with Si-doping, and 3. the $\mathrm{T_C}$ decreases with Si-doping, in contrast to the theoretical prediction. The results will be presented and discussed together with results of other chemical doping in progress. \\[4pt] [1] Takayama, T. et al. Strong Coupling Superconductivity at 8.4 K in an Antiperovskite Phosphide SrPt$_3$P. Physical Review Letters 108, 237001 (2012).\\[0pt] [2] Nekrasov, I. A. \& Sadovskii, M. V Electronic Structure of New Multiple Band Pt-Pnictide Superconductors APt$_3$P 1, 1-5 (2012). [Preview Abstract] |
Wednesday, March 5, 2014 3:42PM - 3:54PM |
Q48.00007: Muon spin relaxation and x-ray/neutron total scattering studies of layered superconductor BaTi2(As,Sb)2O Benjamin Frandsen, Yasumasa Nozaki, Emil Bozin, Hiroshi Kageyama, Simon Billinge, Yasutomo Uemura Layered oxy-pnictide systems such as ATi2Pn2O (A $=$ Na2, Ba, (SrF)2, (SmO)2; Pn $=$ As, Sb, Bi) possess interesting electronic and magnetic properties, including spin/charge density wave (S/CDW) ordering and superconductivity. In addition, they share similarities with the cuprate and iron-pnictide high-Tc compounds, such as planar sheets metal-oxygen sheets, electron/hole-symmetric electron configurations (3d1 and 3d9), and close proximity of density wave and superconducting orders, thus making them intriguing systems to study to gain insight into unconventional superconductivity. BaTi2(As,Sb)2O is a prototypical layered oxy-pnictide system known to have either CDW or SDW ordering for all compositions and superconductivity below 1 K for the Sb endmember. However, it has remained unclear whether the order is CDW or SDW. To investigate this, we have performed muon spin relaxation/rotation and x-ray/neutron total scattering measurements on several specimens. Zero-field muon spin relaxation measurements show no significant increase in relaxation rate at the density wave ordering temperature, indicating that the system undergoes CDW rather than SDW order. Pair distribution function analysis of the total scattering data has yielded insight into the structural details of the CDW transition. [Preview Abstract] |
Wednesday, March 5, 2014 3:54PM - 4:06PM |
Q48.00008: Possible interface superconductivity with coherent quantum CDW transport and soliton condensation phase transition in heterogeneously doped ion implanted NbSe$_{3}$ single crystals Kalyan Sasmal, Dharshana Wijesundera, Irene Rusakova, Wei-Kan Chu, John H. Miller, Zhong Tang, Arnold Guloy Aharonov-Bohm quantum interference shows oscillations of period $h$/2$e$ in conductance \textit{vs}. magnetic flux of CDW rings above 77 K, reveals macroscopically observable quantum behavior. CDW transports electrons through a linear chain compound all together as the Peierls gaps displace in momentum space along with the entire Fermi Sea, similar to a superconductor. The dV/dI vs. bias at several temps showing a significant drop in zero-bias resistance below 46 K across an ion-implanted boundary suggests possible interfacial superconductivity or a related phase transition near the boundary between ion-implanted and un-implanted regions of a CDW in NbSe$_{3}$. The data suggests condensation of solitons near the interface. Charge soliton ($\pm$ 2$e$) dislocations could accumulate and condense near the boundary either due to injected charge from non-isoelectronic impurities or due to a sharp gradient in optimum CDW phase between the weakly and strongly pinned regions. Implanted NbSe$_{3}$ also been studied with TEM. [Preview Abstract] |
Wednesday, March 5, 2014 4:06PM - 4:18PM |
Q48.00009: Dynamical Mean-Field Theory Study of Correlated Electronic Structures and the Phase Diagram of Hydrocarbon Superconductors Minjae Kim, Hong Chul Choi, Ji Hoon Shim, B. I. Min We have studied correlated electronic structures and the phase diagram of electron-doped hydrocarbon molecular solids, based on the dynamical mean-field theory. We have determined the phase diagram of hydrocarbon molecular solids as functions of doping and energy parameters including the Coulomb correlation, the Hund coupling, and the molecular-orbital (MO) energy level splitting. We have found that the hydrocarbon superconductors (electron-doped picene and coronene) belong to the multi-band Fermi liquid state, while non-superconducting electron-doped pentacene belongs to the single-band state in the proximity of the metal-insulator transition. The size of the MO energy level splitting plays an important role in deriving the superconductivity of electron-doped hydrocarbon solids. The multi-band nature of hydrocarbon solids from the small MO energy level splitting boosts the superconductivity through the enhanced density of states at the Fermi level. [Preview Abstract] |
Wednesday, March 5, 2014 4:18PM - 4:30PM |
Q48.00010: What is special with molecular valence 3 in metal-intercalated phenacenes? Sumitendra Mazumdar, Tirthankar Dutta Two important observations are pertinent to the newly discovered metal-intercalated polycyclic aromatic hydrocarbon (PAH) superconductors (examples include, phenanthrene, picene, coronene, and dibenzopentacene): (a) Why are the acenes with linearly fused benezene rings not superconducting? (b) Why does T$_c$ in the PAHs peak only at metal doping $\sim$ 3? In order to address these questions, we have developed a correlated-electron minimal model for phenanthrene ions in solid state, in the reduced space of the two lowest unoccupied molecular orbitals of neutral phenanthrene. Our model is general and can easily be extended to normal states of other PAHs, like, picene and coronene, although the computations would be more demanding. Exact many-body finite cluster calculations on phenanthrene show that while the systems with molecular charges of $-$1 and $-$2 are one- and two-band Mott-Hubbard semiconductors, respectively, molecular charge $-$3 gives two nearly $\frac{3}{4}$-filled bands. The carrier density per active molecular orbital in the superconducting aromatics is nearly the same as that in the organic charge-transfer solids, and we believe that this common carrier density may be the key to understanding unconventional superconductivity in these molecular superconductors. [Preview Abstract] |
Wednesday, March 5, 2014 4:30PM - 4:42PM |
Q48.00011: ABSTRACT WITHDRAWN |
Wednesday, March 5, 2014 4:42PM - 4:54PM |
Q48.00012: Manipulation of a two-photon pump in superconductor -- semiconductor heterostructures Peter P. Orth, Paul Baireuther, Ilya Vekhter, Joerg Schmalian We investigate the photon statistics, entanglement and squeezing of a pn-junction sandwiched between two superconducting leads, and show that such an electrically-driven photon pump generates correlated and entangled pairs of photons. In particular, we demonstrate that the squeezing of the fluctuations in the quadrature amplitudes of the emitted light can be manipulated by changing the relative phase of the order parameters of the superconductors. This reveals how macroscopic coherence of the superconducting state can be used to tailor the properties of a two-photon state. [Preview Abstract] |
Wednesday, March 5, 2014 4:54PM - 5:06PM |
Q48.00013: Probing the unconventional superconductivity of PrPt$_4$Ge$_{12}$ through Ce substitution Kevin Huang, Lei Shu, Ivy Lum, Benjamin D. White, Marc Janoschek, Duygu Yazici, James J. Hamlin, Diego A. Zocco, Pei-Chun Ho, Ryan E. Baumbach, M. Brian Maple Superconductivity has been observed in a new class of filled skutterudite compounds of the form $M$Pt$_{4}$Ge$_{12}$ ($M$ = Sr, Ba, La, Pr, and Th), with the Pr member exhibiting a high superconducting transition temperature $T_c$ $\sim$ 7.9 K. Most of these skutterudite compounds seems to exhibit conventional BCS-type superconductivity; however, superconductivity in Pr appears to be unconventional as it exhibits characteristics of time-reversal symmetry breaking. To help clarify the nature of the superconductivity in PrPt$_4$Ge$_{12}$, we studied the response of superconductivity to the substitution of Ce for Pr throughout the series Pr$_{1-x}$Ce$_x$Pt$_4$Ge$_{12}$ (0 $\leq$ x $\leq$ 1). Measurements of electrical resistivity, magnetic susceptibility, and specific heat were performed and superconductivity were observed up to a Ce concentration of 50$\%$. A pronounced change was observed in the temperature dependence of specific heat below $T_c$ where PrPt$_4$Ge$_{12}$ exhibits a crossover from a $T^3$ to an exponential temperature dependence when Ce is introduced. [Preview Abstract] |
Wednesday, March 5, 2014 5:06PM - 5:18PM |
Q48.00014: Supermetallic and Trapped States in Periodically Driven Lattices Bala Sundaram, Indubala Satija The gapless metallic phases of periodically driven lattices are shown\footnote{Indubala I. Satija and Bala Sundaram, arXiv:0783264, cond-mat-quant-gas} to exhibit unusual resonant transport characteristics where every resonance is accompanied by a pair of anti-resonances. These anti-resonances describe highly coherent, dynamically localized or {\it trapped} states, in sharp contrast with the resonant or {\it supermetallic} states where the quantum dynamics describes free propagation. The supermetallic states are related to the integer winding of the quasienergy spectrum and are characterized by a band structure that is topologically a circle. In the context of novel phases of matter, our study elucidates important distinctions between static and driven systems that pave the way for engineering a variety of band structures resulting in free, trapped as well as flat band states. [Preview Abstract] |
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