Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session W35: Novel Superconductors II |
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Sponsoring Units: DCMP Chair: Meigan Aronson, Brookhaven National Laboratory Room: 343 |
Thursday, March 21, 2013 2:30PM - 2:42PM |
W35.00001: Evolution of superconductivity and magnetic order in LaRu$_3$Si$_2$ by rare earth and transition metal substitutions. Renxiong Wang, Shanta R. Saha, Johnpierre Paglione, Daniel Pratt, Qingzhen Huang, Jeffrey W. Lynn The recent discovery of high temperature superconductivity in iron based materials has renewed interest to condensed matter physics. Although its mechanism is not yet settled completely, it should have a close relationship with the electron correlations. The compound LaRu$_{3}$Si$_{2}$ shows superconductivity with a transition temperature $T_{\mathrm{c}}=$ 7.8 K. Recent study indicates that electron correlations play a significant role for superconductivity in this Kagome lattice of Ru and the Ru band dominates at the Fermi level, similar to Fe-band in iron-superconductors. Superconductivity in LaRu$_{3}$Si$_{2}$ has been found robust against the local paramagnetic moment. We will present our study on the evolution of superconductivity and magnetic order in LaRu$_{3}$Si$_{2}$ due to substitutions of Tm, a J$=$6 (J is the total angular momentum) ion with a maximum ordered moment of 7 $\mu_{\mathrm{B}}$, and transition metals by measuring magnetic, transport and Neutron scattering properties. [Preview Abstract] |
Thursday, March 21, 2013 2:42PM - 2:54PM |
W35.00002: Possible Pressure Driven Quantum Critical Point in CaCo$_{2}$P$_{2}$ Ryan E. Baumbach, Xin Lu, Vladimir Sidorov, Filip Ronning, Eric D. Bauer, Joe D. Thompson We performed electrical resistivity measurements under pressures up to a maximum of $\approx $ 5 GPa for the d-electron antiferromagnet CaCo$_{2}$P$_{2}$,$_{\, }$where we find that the N\'{e}el temperature (T$_{N} \quad =$ 106 K) is rapidly suppressed towards zero near 1.4 GPa. In the vicinity of the suppressed magnetic state, the Fermi liquid coefficient of the electrical resistivity A increases abruptly, suggesting a divergence in the effective mass of the charge carrier quasiparticles. In addition, we find that the residual resistivity $\rho_{0}$ increases abruptly at 1.4 GPa. For P \textgreater 1.4 GPa, we also observe a broad hump in $\partial \rho $/$\partial $T at a temperature T*, which increases with increasing P. We will compare these measurements to expectations for prototypical f-electron quantum critical point (QCP) systems (e.g., CeRhIn$_{5}$ and CeRh$_{2}$Si$_{2})$ and the iron arsenide high temperature superconductors (e.g., CaFe$_{2}$As$_{2}$, SrFe$_{2}$As$_{2}$, and BaFe$_{2}$As$_{2})$ and discuss implications for studying a possible d-electron QCP in the absence of superconductivity. [Preview Abstract] |
Thursday, March 21, 2013 2:54PM - 3:06PM |
W35.00003: Universal scaling relations in exotic superconductors S.V. Dordevic, D.N. Basov, C.C. Homes Universal scaling relations are of tremendous importance in science, as they reveal fundamental laws of nature. Several such scaling rations have recently been proposed for superconductors, however, they are not really universal in a sense that some important families of superconductors appear to fail the scaling, or obey the scaling with different scaling pre-factors. In particular, a large group of materials called organic (or molecular) superconductors are a notable example. In this paper we show that such apparent violations are largely due to the fact that the required experimental parameters were collected on different samples, with different experimental techniques. When experimental data is taken on the same sample, using a single experimental technique, organic superconductors, as well as all other studied superconductors, do in fact follow universal scaling relations. [Preview Abstract] |
Thursday, March 21, 2013 3:06PM - 3:18PM |
W35.00004: Anomalous thermodynamic power laws in nodal superconductors Jorge Quintanilla, Bayan Mazidian, James F. Annett, Adrian D. Hillier Unconventional superconductors are frequently identified by the observation of power law behaviour on low temperature thermodynamic properties such as specific heat. These power laws generally derive from the linear spectrum near points or lines of zeros, or nodes, in the superconducting energy gap on the Fermi surface. Here we show that, in addition to the usual point and line nodes, a much wider class of different nodal types can occur. Some of these new types of nodes typically occur when there are transitions between different types of gap node topology, for example when point or line nodes first appear as a function of some physical parameter. We derive anomalous, non-integer thermodynamic power laws associated with these new nodal types and predict their occurrence in iron pnictide superconductors and in the noncentrosymmetric system Li$_{2}$Pd$_{3-x}$Pt$_{x}$B. [Preview Abstract] |
Thursday, March 21, 2013 3:18PM - 3:30PM |
W35.00005: Anomalous angular dependence of the upper critical induction of orthorhombic ferromagnetic superconductors with completely broken $p$-wave symmetry Christopher L\"orscher, Jingchuan Zhang, Qiang Gu, Richard Klemm We calculate the angular dependence of the upper critical field, $H_{c2}(\theta,\phi,T)$,
for an orthorhombic ferromagnetic superconductor with a general ellipsoidal
Fermi surface with effective masses $m_{1}$, $m_{2}$, and $m_{3}$,
in which we have $p$-wave parallel-spin pairing that is locked onto
the $z$-axis direction. We report anomalous angular dependence of
$H_{c2}$ for fixed $3 |
Thursday, March 21, 2013 3:30PM - 3:42PM |
W35.00006: Triplet Nodeless Superconductivity Scenario in the Quasi-One-Dimensional Layered Conductor Li$_{0.9}$Mo$_6$O$_{17}$ Andrei Lebed, Otar Sepper We solve a theoretical problem about the upper critical magnetic field, parallel to a conducting axis of a layered quasi-one-dimensional superconductor. In particular, we consider the case, where triplet superconducting order parameter is not sensitive to the Pauli destructive effects against superconductivity and has no zeros on two quasi-one-dimensional pieces of the Fermi surface. We demonstrate [1] that in this case the orbital destructive effects against superconductivity can destroy superconducting state at magnetic fields much higher than the so-called Clogston-Chandrasekhar paramagnetic limit. Comparison of our theoretical results with the very recent experimental data [2] is in favor of a triplet superconducting pairing in the layered quasi-one-dimensional superconductor Li$_{0.9}$Mo$_6$O$_{17}$.\\[4pt] [1] A.G. Lebed and O. Sepper, Phys. Rev. Lett., submitted.\\[0pt] [2] J.-F. Mercure et al., Phys. Rev. Lett. \textbf{108}, 187003 (2012). [Preview Abstract] |
Thursday, March 21, 2013 3:42PM - 3:54PM |
W35.00007: Ferromagnetism in CuFeSb: Evidence of competing magnetic interactions in Fe-based superconductors Jin Hu, Bin Qian, J. Lee, Gaochao Wang, P. Kumar, Minghu Fang, Tijiang Liu, David Fobes, H. Pham, L. Spinu, Xiaoshan Wu, M. Green, S.H. Lee, Zhiqiang Mao In this talk, we will report a new layered iron-pnictide compound CuFeSb [1]. This material shares similar layered tetragonal structure with iron-based superconductors, with Fe square planar sheets forming from the edge-sharing iron antimony tetrahedral network. CuFeSb differs remarkably from Fe-based superconductors in the height of anion Z$_{anion}$ from the Fe plane; Z$_{Sb}$ for CuFeSb is $\sim$1.84 {\AA}, much larger than Z$_{As}$ (1.31-1.51 {\AA}) in FeAs compounds and Z$_{Te}$ ($\sim$1.77 {\AA}) in Fe$_{1+y}$Te. In contrast with the metallic antiferromagneticor superconducting state of iron pnictides and chalcogenides under current studies, CuFeSb exhibits a metallic, ferromagnetic state with $T_{c} =$ 375 K. This finding provide strong experimental evidence for the competition between antiferromagnetic and ferromagneticcorrelations in layered Fe-based superconductors, and that the nature of magnetic coupling within the Fe plane is indeed dependent on the height of anion as predicted in theories [2,3].\\[4pt] [1] B. Qian\textit{ et al.}, Phys. Rev. B \textbf{85}, 144427 (2012).\\[0pt] [2] C.-Y. Moon,\textit{ et a.l}, Phys. Rev. Lett \textbf{104}, 057003 (2010).\\[0pt] [3] W.-G. Yin, \textit{et al.}, Phys. Rev. Lett \textbf{105}, 107004 (2010). [Preview Abstract] |
Thursday, March 21, 2013 3:54PM - 4:06PM |
W35.00008: Selective $d$-band Participation in Magnetic and Electronic Behavior of Spin-Ladder Iron-chalcogenides Joseph Caron, James Neilson, David Miller, Vadim Ksenofontov, Claudia Felser, Kathrine Arpino, Anna Llobet, Tyrel McQueen The mechanism of superconductivity in the iron-based superconductors, particularly the role of magnetism and band nesting, remains controversial. The iron-based superconductors share many properties with the high-$T_c$ cuprates, including two-dimensional layers and proximity to magnetic order. Using reduced dimensionality, as exemplified by the ``spin ladder'' cuprates, we attempt to understand the electronic and magnetic behavior of the $A$Fe$_2X_3$ ($A$= alkali or alkali earth, $X$ = chalcogenide) family of materials. These compounds have $2\times \infty$ double-chains (``ladders'') of edge-sharing Fe$X_4$ tetrahedra, cutouts of the full two-dimensional Fe$_2X_2$ layers of the iron-based superconductors which provide a platform from which to understand the interplay of structure, magnetism, and electronic behavior. The unique properties of these compounds is exemplified by both the inability of DFT programs recapitulate either the underlying physical properties or the dramatic transition from block to stripe magnetic order in Ba$_{1-x}$K$_x$Fe$_2$Se$_3$ that coincides with a change from magnetic to non-magnetic behavior of one $d$- orbital-derived band. I will also present the influence of pressure and chemical doping on metallic and/or superconducting behavior. [Preview Abstract] |
Thursday, March 21, 2013 4:06PM - 4:18PM |
W35.00009: Physical properties of Kx(Ni,Fe)2-ySe2 single crystal alloys1 Hyejin Ryu, Hechang Lei, Kefeng Wang, D. Graf, Emil S. Bozin, J. B. Warren, C. Petrovic We report physical properties and ground state phase diagram of Kx(Fe,Ni)2-ySe2 single crystal alloy series. The ground state evolves from a heavy-Fermion-like metal KxNi2-ySe2 (I4/mmm) to a phase separated superconducting KxFe2-ySe2 (I4/m and I4/mmm space groups). Intermediate alloys show rich variety of ground states including semiconducting magnetic spin glass as Ni is replaced by Fe. We will address magnetic, thermodynamic, electronic and thermal transport properties and their connection to relevant structural parameters. 1Work at Brookhaven is supported by the U.S. DOE under Contract No. DE-AC02-98CH10886 and in part by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. DOE, Office for Basic Energy Science (H. L. and C. P). Work at the National High Magnetic Field Laboratory is supported by the DOE NNSA DEFG52-10NA29659 (D.G.), by the NSF Cooperative Agreement No. DMR-0654118, and by the state of Florida. [Preview Abstract] |
Thursday, March 21, 2013 4:18PM - 4:30PM |
W35.00010: Physical and magnetic properties of LaFe$_{0.6}$Sb$_{2}$ Jennifer Misuraca, J.E. Grose, J.W. Simonson, C. Marques, J. Liu, G. Smith, A. Puri, J. Hassinger, M.C. Aronson Currently, there is a tremendous effort to grow and characterize new iron pnictide materials with the hopes of discovering the next set of novel high temperature superconductors. The previous research has been focused on iron phosphides and arsenides, with relatively little work being done on the next heavier pnictogen, antimony. In this work, single crystals of the layered iron pnictide LaFe$_{0.6}$Sb$_{2}$ have been grown with the ZrCuSi$_{2}$ structure with vacancies on the Fe sites as determined via x-ray diffraction and energy-dispersive x-ray spectroscopy. The DC magnetization, resistivity, and heat capacity have been measured in a range of temperatures between 300 K and 0.5 K. The susceptibility is small and shows very little anisotropy; there is a maximum at 265 K and we see no Curie-Weiss-like behavior from room temperature down to 1.8 K. This material is a good metal whose resistivity decreases by a factor of 1.4 from 300 K to 0.5 K and we see Fermi liquid-like behavior from 7 K to 20 K. Although there is no evidence of bulk superconductivity down to 0.5 K in this undoped material, a large Sommerfeld coefficient of 50 mJ/(mol Fe) K$^{2}$ suggests that this metal is very strongly correlated. [Preview Abstract] |
Thursday, March 21, 2013 4:30PM - 4:42PM |
W35.00011: Quasi-two-dimensional non-collinear magnetism in the Mott insulator Sr$_2$F$_2$Fe$_2$OS$_2$ Shan Wu, C. Broholm, Liang L. Zhao, Jiakui K. Wang, E. Morosan, J.P. Hodges We study the magnetism of Sr$_2$F$_2$Fe$_2$OS$_2$ through neutron powder diffraction and thermodynamic and transport measurement. Quasi-two-dimensional magnetic order develops below $T_{\rm N}$=106K with an in-plane correlation length exceeding 310 {\AA} and an out-of-plane correlation length of only 17(3) {\AA}. The data are well described by a two-k structure with k$_1$=(1/2,0,1/2) and k$_2$=(0,1/2,1/2). The ordered moment is 3.3(1) $\mu_B$ oriented along the in-plane components of k. This structure is composed of orthogonal AFM chains intersecting at super-exchange mediating O sites. The Density Function Theory ( by Liang L.Zhao, Jiakui K. Wang, etc.) also leads to this structure and a narrower Fe 3d band than for the iron pnictides from which electronic correlations produce a Mott insulator. [Preview Abstract] |
Thursday, March 21, 2013 4:42PM - 4:54PM |
W35.00012: Functional interfaces in La$_{2/3}$Ca$_{1/3}$MnO$_{3}$/ YBa$_{2}$Cu$_{3}$O$_{7-x}$ heterostructures Tra Vu Thanh, Ying-Jiun Chen, Hong-Ji Lin, Jiunn-Yuan Lin, Ying-Hao Chu Interfaces have emerged as one of the focal points of current condensed matter science. In complex, correlated oxides, heterointerfaces provide a powerful route to create and manipulate the charge, spin, orbital, and lattice degrees of freedom. In this study, epitaxial bilayers of ferromagnetic of La$_{2/3}$Ca$_{1/3}$MnO$_{3}$(LCMO) and superconducting YBa$_{2}$Cu$_{3}$O$_{7-x}$ (YBCO) with two distinct interfaces have been fabricated to understand the effects of these two distinct interfaces. X-ray absorption near edge spectroscopy (XANES) was applied to characterize the interfaces and also provided direct evidence of the charges transfer at these interfaces. The studies of the macroscopic properties, such as the transport and magnetic properties, established the connection between macroscopic properties and the interface structures. This present study opens new venue to design the functional interfaces. [Preview Abstract] |
Thursday, March 21, 2013 4:54PM - 5:06PM |
W35.00013: Superconducting interface in cuprate p-n heterostructures Maxime Dion, Laurent Olivier, Guillaume Hardy, S\'ebastien Godin-Proulx, Patrick Fournier In this explorative work, we combined two kinds of non-superconducting cuprates : over-doped ${\rm Pr}_{2-x}{\rm Ce}_x{\rm CuO}_4$ and under-doped ${\rm La}_{2-x}{\rm Sr} _x{\rm CuO}_4$ in the same p-n heterostructures in order to generate new behaviors through the interplay between the two materials. We will show that a thin superconducting layer ($<10$ nm) arise at the interface between these two compounds. We will discuss its actual location, its unexpected occurrence and its origin which is partly compatible with a charge transfer scenario that takes place in similar p-p cuprate heterostructures [1,2].\\[4pt] [1] A. Gozar \textit{et al.}, Nature 456, 782 (2008)\\[0pt] [2] G. Logvenov \textit{et al.}, Science 326, 699 (2009) [Preview Abstract] |
Thursday, March 21, 2013 5:06PM - 5:18PM |
W35.00014: Electron Doping by Charge Transfer at LaFeO$_3$/Sm$_2$CuO$_4$ Epitaxial Interfaces Jacobo Santamaria, F.Y. Bruno, M. Varela, J. Garcia-Barriocanal, A. Rivera, R. Schmidt, C. Leon, P. Thakur, J.C. Cezar, N.B. Brookes, M. Garcia Hernandez, E.R. Dagotto, S.J. Pennycook We examine the interfacial charge transfer in epitaxial heterostructures formed between Mott insulating Sm$_2$CuO$_4$ (SCO) and charge transfer insulator LaFeO$_3$ (LFO) in LFO/SCO superlattices. High resolution EELS measurements at the O-K edge have provided evidence for 0.09$+$/-0.01 extra electrons in the SCO d- band as revealed by a reduction of the Cu oxidation state. The transfer of electrons from LFO to SCO is further supported by the spectroscopic signature of Cu$^{1+}$ as obtained from XAS measurements. Transport measurements have evidenced a metallic state at the interface between two nominally insulating materials. Dielectric spectroscopy measurements have allowed ascribing the metallic state to the LFO/SCO interfaces, consistent with DC measurements. When lowering the temperature a metal to insulator transition occurs at 120 K, indicating, in accordance with the phase diagram, an insufficient doping level to enter a superconducting state. [Preview Abstract] |
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