Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session H39: Novel Superconductors IAcoustics
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Jim Eckstein, University of Illinois Room: 386 |
Tuesday, March 14, 2017 2:30PM - 2:42PM |
H39.00001: Enhancement of spin-lattice relaxation rate of $\beta$$^{\prime\prime}$-(BEDT-TTF)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$ in its high-field superconducting phase Hsin-Hua Wang, Georgios Koutroulakis, Sebastian Molatta, Hannes K\"{u}hne, Yue-shun Su, John Schlueter, Joachim Wosnitza, Stuart Brown We report a $^{13}$C NMR study of an organic charge transfer salt $\beta$$^{\prime\prime}$-(BEDT-TTF)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$, focusing on the spin dynamics in its high-field inhomogeneous superconducting phase, a putative FFLO state. A noticeable enhancement of the spin-lattice relaxation rate beyond the normal state value is observed within the limits of the FFLO phase for a range of fields at T=750mK, resembling similar features previously observed in the related compound $\kappa$-ET. This enhancement is suppressed upon cooling, and its freeze-out is investigated in detail. Moreover, the angular dependence of the relaxation rate in the vicinity of the aligned in-plane field condition is probed, in an effort to inform the origin of the observed behavior with orbital or hyperfine effects. [Preview Abstract] |
Tuesday, March 14, 2017 2:42PM - 2:54PM |
H39.00002: New details in the superconducting phase diagram of $\lambda\text{-(BETS)}_2\text{GaCl}_4$: further evidence of a FFLO phase Logan Bishop-Van Horn, Raju Ghimire, Jordan Resta, William Coniglio, Scott Hannahs, Akiko Kobayashi, Charles Agosta New low-noise rf penetration depth measurements of the high-field superconducting state in the quasi-2d organic superconductor $\lambda\text{-(BETS)}_2\text{GaCl}_4$ are presented and compared to previous measurements of the same material\footnote{Coniglio, \emph{et al.}, Phys. Rev. B \textbf{83}, 224507 (2011)}$^,$\footnote{Mielke, \emph{et al.}, J. Phys.: Condens. Matter {\bf 13} (2001)}. The new data show very clear indication of a phase transition within the superconducting state, with the position of the $H_\text{P}$ phase line significantly lower than in less clean samples, while the $H_\text{c2}$ phase line is unchanged. Shubnikov-de Haas oscillations, previously never seen below 32 T in this material$^2$, are observed at fields as low as 13 T, indicating that there is less scattering in these new samples. $H_\text{c2}$ is usually sensitive to spin-orbit scattering, suggesting that the unchanged upper critical field is not traditional, but rather the destruction of a FFLO state. In contrast, $H_\text{P}$ should still be sensitive to changes of the spin-orbit scattering rate, consistent with the new data. [Preview Abstract] |
Tuesday, March 14, 2017 2:54PM - 3:06PM |
H39.00003: Correlated model calculations of $\beta$ phase organic superconductors R. Torsten Clay, S. Mazumdar The quasi-two-dimensional organic charge-transfer salts of the $\beta$ and $\beta^\prime$ structures display a wide range of electronic behavior including antiferromagnetism (AFM), charge ordering (CO), and superconductivity (SC). In the temperature-pressure phase diagram, CO is found adjacent to SC. In the $\beta$ structure stacks of $\frac{3}{4}$-filled (one half hole per molecule) organic molecules are strongly dimerized. The presence of CO adjacent to SC is of particular interest as one carrier per dimer gives an effectively half-filled band that should instead favor AFM. We show that the charge ordered state evolving into SC in these materials is a Paired Electron Crystal, with singlet formation between dimers giving a spin gap simultaneous with charge order. We present the results of calculations within a two-dimensional $\frac{3}{4}$-filled Hubbard model using the Path Integral Renormalization Group (PIRG) and quantum Monte Carlo methods. Our results demonstrate that electron-electron interactions enhance the long-range pair-pair correlations for SC of d-wave symmetry preferentially at density 0.5. We further discuss the effect of lattice frustration on pairing and CO in this class of materials. [Preview Abstract] |
Tuesday, March 14, 2017 3:06PM - 3:18PM |
H39.00004: Crossover in electronic states of fulleride superconductors revealed by electrical transport Yuki Matsuda, Satoshi Heguri, Katsumi Tanigaki Cs$_{3}$C$_{60}$ fullerides with A15 structure found in 2008 [1] and fcc structure in 2010 [2] show superconducting transition at 38K and 35K under pressure, respectively. Both structural phases are Mott insulators in the entire temperature range at ambient pressure. High pressure drives them into metallic and superconducting states and the highest superconducting critical temperature was found at the boundary between unconventional superconducting and conventional BCS superconducting states [1-6]. Recently, we have successfully performed electrical transport measurements on fulleride superconductor families by using a specially designed pressure cell. We will comment on the details of the electronic crossover region of $A_{3}$C$_{60}$ ($A \quad =$ alkali metal) fullerides on a basis of both magnetic [6] and electrical transport measurements. Our new finding by electrical transport can provide a further understanding for highly electron-correlated unconventional molecular superconductors. [1] A. Y. Ganin \textit{et al.}, \textit{Nat. Mater}. \textbf{7}, 367 (2008). [2] A. Y. Ganin \textit{et al.}, \textit{Nature} \textbf{466}, 221 (2010). [3] Y. Takabayashi \textit{et al.}, \textit{Science}, \textbf{323}, 1585 (2009). [4] N. Iwahara, \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{111}, 056401 (2013). [5] N. Iwahara, \textit{et al.}, \textit{Phys. Rev. B} \textbf{91}, 035109 (2015). [6] R. H. Zadik \textit{et al.}, \textit{Sci. Adv.} \textbf{1}, e1500059 (2015). [Preview Abstract] |
Tuesday, March 14, 2017 3:18PM - 3:30PM |
H39.00005: Enhancing superconductivity of A$_{\mathrm{3}}$C$_{\mathrm{60}}$ fullerides : mechanism and its relation to optically stimulated superconductivity Minjae Kim, Yusuke Nomura, Michel Ferrero, Priyanka Seth, Olivier Parcollet, Antoine Georges Recently, there was a remarkable observation of the nonequilibrium superconductivity (SC) up to \textasciitilde 100 K in K$_{\mathrm{3}}$C$_{\mathrm{60}}$ fullerides by terahertz (THz) optical pump prove experiment.[Ref.[1]] This temperature (T) of nonequilibrium SC is much higher than T$_{\mathrm{c}}$ of equilibrium (20K). Motivated by the experiment, we investigate how perturbation effects on SC of A$_{\mathrm{3}}$C$_{\mathrm{60}}$ by using the strong-coupling model. We have shown that the perturbation such that smaller Coulomb interaction in two of three LUMO of C$_{\mathrm{60}}$ enhances T$_{\mathrm{c}}$ of fullerides, potentially up to factor of 1.8. We have shown that this type of perturbation could be realized in the pump prove experiment by T$_{\mathrm{1u}}$(4) phonon excitation which is suggested to be pumped from the THz light. Other types of perturbations are detrimental to the SC of fullerides. The mechanism of T$_{\mathrm{c}}$ of fullerides is that (i) stabilization of spin-singlet states, and (ii) preservation orbital fluctuation. This finding provides guideline for experiment to observe an enhancement of T$_{\mathrm{c}}$ and basis for theoretical investigation of nonequilibrium phenomena of fullerides. [1] M. Mitrano et al., Nature 530, 461 (2016). [Preview Abstract] |
Tuesday, March 14, 2017 3:30PM - 3:42PM |
H39.00006: Orbital disproportionation of electronic density is a universal feature of alkali-doped fullerides Naoya Iwahara, Liviu Chibotaru Alkali-doped fullerides A$_n$C$_{60}$ show a remarkably wide range of electronic phases in function of A = Li, Na, K, Rb, Cs and the degree of doping, $n=$ 1-5. While the presence of strong electron correlations is well established, recent investigations give also evidence for dynamical Jahn-Teller instability in the insulating and the metallic phase of A$_3$C$_{60}$ [1, 2]. To reveal the interplay of these interactions in fullerides with even $n$, we address the electronic phase of A$_4$C$_{60}$ with accurate many-body calculations within a realistic electronic model including all basic interactions extracted from first principles [3]. We find that the Jahn-Teller instability is always realized in these materials too. More remarkably, in sharp contrast to strongly correlated A$_3$C$_{60}$, A$_4$C$_{60}$ displays uncorrelated band-insulating state despite pretty similar interactions present in both fullerides. Our results show that the Jahn-Teller instability and the accompanying orbital disproportionation of electronic density in the degenerate LUMO band is a universal feature of fullerides. [1] N. I. and L. F. C., Phys. Rev. Lett. 111, 056401 (2013). [2] N. I. and L. F. C., Phys. Rev. B 91, 035109 (2015). [3] N. I. and L. F. C., Nat. Commun. 7, 13093 (2016). [Preview Abstract] |
Tuesday, March 14, 2017 3:42PM - 3:54PM |
H39.00007: Highly responsive ground state of PbTaSe$_2$: structural phase transition and evolution of superconductivity under pressure S. L. Budko, U. S. Kaluarachchi, Y. Deng, M. F. Besser, K. Sun, L. Zhou, M. C. Nguyen, C. Zhang, J. S. Schilling, M. J. Kramer, S. Jia, C. Z. Wang, K. M. Ho, P. C. Canfield Thermodynamic and transport studies of PbTaSe$_2$ under pressure suggest existence of two superconducting phases with the phase boundary at $\sim 0.25$ GPa at low temperatures that is defined by a very steep, first order, structural, phase transition. The structural phase transition line extends to $\sim 425$ K at ambient pressure as evidenced by transmission electron microscopy and x-ray diffraction at elevated temperatures. The new, high temperature / high pressure phase has similar crystal structure and slightly lower unit cell volume. The details of this new structute were identified based on first-principles total energy calculations. [Preview Abstract] |
Tuesday, March 14, 2017 3:54PM - 4:06PM |
H39.00008: Electronic Structure Calculations of Filled Skutterudites RGe$_{4}$Pt$_{16}$ Khandker Quader, Michael Widom, Lucian Pascut We present a comparative study of the filled skutterudites RGe$_{4}$Pt$_{16}$ (R=La, Ce, Pr), based on T=0 density functional theory (DFT) calculations. To elicit possible role of the lanthanide f-electrons and f-f interaction U, we calculate band structures, Fermi surfaces and density of states (DOS) for different scenarios: (a) frozen f-electron GGA; (b) unfrozen f-electron GGA + U with spin-orbit coupling; (c) unfrozen f-electron GGA with spin-orbit coupling. Comparison of our DFT DOS with experimental electronic heat capacity suggest a modest values of m$^{*}$/m$_{\rm band}$. Our calculated Fermi surface topology near Fermi energy may provide clues into the occurrence of superconductivity in the La and Pr compounds and the non-occurrence in the Ce one. Our T=0 calculations of magnetism at zero doping and pressure show that Pr has a large moment and is ferrimagnetic; Ce has a very weak moment and marginally favors antiferromagnetism. We explore if the experimentally observed variation of superconducting T$_{C}$ with pressure in the Pr compound can be accounted for in terms of the variation of DOS with pressure. [Preview Abstract] |
Tuesday, March 14, 2017 4:06PM - 4:18PM |
H39.00009: Strange thermal transport properties of (Ca$_x$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$ below the superconducting transition temperature Xiaoye Chen, Swee K. Goh, Hibiki Kanagawa, Masaki Imai, Kazuyoshi Yoshimura, Michael Sutherland The quasi-skutterudite superconducting material family (Ca$_x$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$ have a composition induced structural quantum phase transition that can be suppressed to zero temperature. \footnote{S. Goh et al., Phys. Rev. Lett. \textbf {114}, 097002 (2015).} The resulting soft phonon modes bring about many intriguing effects, like increasing electron-phonon coupling and enhanced superconductivity. \footnote{W. C. Yu et al., Phys. Rev. Lett. \textbf {115}, 207003 (2015).} At temperatures well below the superconducting transition temperature $T_c$, we expect the thermal conductivity of the sample to be dominated by phonons, which in the boundary scattering limit, is proportional to $T^3$ - the temperature dependence of the heat capacity. Here, we discuss the thermal conductivity measurement of six samples of (Ca$_x$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$ spanning the phase diagram, and show that the thermal conductivity exhibits a temperature dependence that is well below $T^3$ near the critical doping. Through a comparison with other thermodynamic measurements as well as theoretical calculations, we consider the consequences of scattering from soft phonon modes near the critical region for heat transport. [Preview Abstract] |
Tuesday, March 14, 2017 4:18PM - 4:30PM |
H39.00010: Superconductivity in multiple phases of compressed GeSb$_{\mathrm{\mathbf{2}}}$\textbf{Te}$_{\mathrm{\mathbf{4}}}$ Alexander Palevski, Eran Greenberg, Bar Hen, Samar Layek, Irina Pozin, Michael Karpovski, Victor Shelukhin, Moshe Paz, Gregory Rozenberg, Yoram Dagan, Yuri Rosenberg, Roee Friedman, Eran Sterer Here we report the discovery of superconductivity in multiple phases of the compressed GeSb$_{\mathrm{2}}$Te$_{\mathrm{4\thinspace }}$(GST) phase change memory alloy, which has attracted considerable attention for the last decade due to its unusual physical properties with many potential applications. Superconductivity is observed through electrical transport measurements, both for the amorphous (a-GST) and for the crystalline (c-GST) phases. The superconducting critical temperature, T$_{\mathrm{c}}$, continuously increases with the applied pressure reaching a maximum T$_{\mathrm{c\thinspace }}=$6K at P$=$20 GPa for a-GST, whereas the critical temperature of the cubic phase reaches a maximum T$_{\mathrm{c\thinspace }}=$8 K at 30 GPa. This new material system, exhibiting a superconductor-insulator quantum phase transition (SIT) has an advantage over disordered metals since it has a continuous control of the crystal structure and the electronic properties using pressure as an external stimulus, which was lacking in SIT studies until today. [Preview Abstract] |
Tuesday, March 14, 2017 4:30PM - 4:42PM |
H39.00011: Second-order Structural Transition in Superconductor La$_3$Co$_4$Sn$_{13}$ Yiu Wing Cheung, Jingzhao Zhang, Junyi Zhu, Wing Chi Yu, Yajian Hu, Dige Wang, Yuka Otomo, Kazuaki Iwasa, Koji Kaneko, Masaki Imai, Hibiki Kanagawa, Kazuyoshi Yoshimura, Swee Kuan Goh The family of the superconducting quasiskutterudite with general chemical formula R$_3$T$_4$Sn$_{13}$ (R = Ca, Sr; T = Rh, Ir) was recently found to feature a structural transition at $T*$. The structural transition can be tuned to a structural quantum critical point by chemical and/or physical pressure, around which a dome-shaped variation of the superconducting transition temperature $T_c$ is found. Similar behavior was found in the isostructural compound La$_3$Co$_4$Sn$_{13}$, although there is currently a dispute in the literature regarding the nature of $T*$ transition. To shed light on the interplay of structural instability and superconductivity, we performed resistivity, specific heat and X-ray diffraction measurements on La$_3$Co$_4$Sn$_{13}$, focusing particularly on their temperature dependence around $T*$. Our results, in combination with lattice dynamics calculations, are more consistent with the second-order nature of the phase transition at $T*$. [Preview Abstract] |
Tuesday, March 14, 2017 4:42PM - 4:54PM |
H39.00012: Time Reversal Symmetry of A and B phases of PrOs$_4$Sb$_{12}$ Eli Levenson-Falk, Elizabeth Schemm, Ruby Shi, M. Brian Maple, Aharon Kapitulnik The heavy-fermion superconductor PrOs$_4$Sb$_{12}$ has attracted great interest because of the existence of two superconducting transitions at zero magnetic field. However, there is great debate over whether the two superconducting phases (A and B) corresponding to these transitions are intrinsic or simply the result of impurity-induced inhomogeneities. Further, there is strong evidence for time reversal symmetry breaking (TRSB) in the superconducting state. We present polar Kerr effect measurements of PrOs$_4$Sb$_{12}$ crystals. By moving the focused optical spot over the surface of our samples, we are able to discern whether the strength and onset temperature of TRSB is homogeneous over the entire crystal. [Preview Abstract] |
Tuesday, March 14, 2017 4:54PM - 5:06PM |
H39.00013: Crossover and coexistence of superconductivity and antiferromagnetism in the filled-skutterudite system Pr$_{\mathrm{1-}}_{x}$Eu$_{x}$Pt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$. I. Jeon, A. J. Breindel, B. Luong, M. B. Maple, P.-C. Ho, R. B. Adhikari, C. C. Almasan We studied the superconducting and normal-state properties of the unconventional superconductor PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$, in which Eu has been substituted for Pr. Polycrystalline samples of Pr$_{\mathrm{1-}}_{x}$Eu$_{x}$Pt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$ were investigated via x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. Upon Eu substitution, we observed a crossover from superconducting to antiferromagnetically ordered states with a region where superconductivity and antiferromagnetism coexist. In the superconducting region, the specific heat data exhibit a change of temperature dependence, suggesting an alteration from a nodal to nodeless superconducting energy gap or suppression of multiband superconductivity. This change is relatively slower than previous reports for different substituent ions, suggesting that paramagnetic impurities have a weaker pair breaking effect on unconventional superconductivity in PrPt$_{\mathrm{4}}$Ge$_{\mathrm{12}}$. In the normal state, we observed an evolution from Fermi-liquid to non-Fermi-liquid behavior, accompanying the coexistence of superconductivity and antiferromagnetism, suggesting the electronic band structure is closely related to the complex physical phenomena in this system. This work was supported by the Grant No. DOE-DE-FG02-04-ER46105, and NSF-DMR-1206553 and 1506677. The work at KSU was supported by the Grant No. NSF-DMR-1505826. [Preview Abstract] |
Tuesday, March 14, 2017 5:06PM - 5:18PM |
H39.00014: Ternary chalcogenide superconductor with rock salt structure Kaya Kobayashi, Teppei Ueno, Jun Akimitsu Binary chalcogenide semiconductor, SnTe, becomes superconducting when deficiency of tin or In is doped. Despite the carriers introduced is estimated the same for several dopants, In strongly modulates the electronic structure and superconductivity. We have synthesized superconductor with rock salt structure, Ag1-xS1$+$xSe2 as a reference of the aforementioned material. Several dopants give insight of how superconductivity is modulated by the valence state of tin. [Preview Abstract] |
Tuesday, March 14, 2017 5:18PM - 5:30PM |
H39.00015: Molecular Model for Chevrel Phase Superconductivity Jia Chen, Andrew Millis, David Reichman Inspired by the search for emergent properties in molecular assemblies, we studied superconductivity in chevrel phase compounds, which are built on Mo$_6$X$_8$ (X= S, Se, Te) molecular clusters. We used density functional and density functional perturbation theory to calculate the coupling between partially filled molecular orbitals and vibrational modes, thereby identifying the E $\otimes$ e Jahn-Teller interaction as a crucial coupling. Many-body (Eliashberg and dynamical mean field based) methods are used build a theory for superconductivity. Insights from this work that can be used to guide discovery of additional superconductors will be discussed. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700