Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Q52: Physical Properties of Copper-oxide Superconductors |
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Sponsoring Units: DCMP Chair: Antony Carrington, University of Bristol Room: Mile High Ballroom 1F |
Wednesday, March 5, 2014 2:30PM - 2:42PM |
Q52.00001: In-plane Anisotropic Superconductivity in YBa$_{2}$Cu$_{3}$O$_{7-\sigma}$/ BiFeO$_{3}$ Heterostructure Yen-Lin Huang, Ying-Hao Chu We demonstrate a correlation between the periodic domain structure of multiferroic BiFeO$_{3}$ thin films and the anisotropic superconducting of YBa$_{2}$Cu$_{3}$O$_{7-\sigma}$/BiFeO$_{3}$ heterostructures. Two types of periodic domain structures in BFO -- 71$^{\circ}$ and 109$^{\circ}$ are used to manipulate the superconductor, YBCO, and an anomalous superconducting behavior, which shows different transition regions parallel or perpendicular to the domain walls of BFO respectively, is observed. The superconducting transition region is much broader when the current goes perpendicularly to the domain walls in BFO than parallel. The difference of Tc is about 40 K, in other words the YBCO shows one dimensional superconducting behavior within 40 K. [Preview Abstract] |
Wednesday, March 5, 2014 2:42PM - 2:54PM |
Q52.00002: Evolution of the Superconductivity Dome in the two dimensional Hubbard Model Kuang-Shing Chen, Ziyang Meng, Shuxiang Yang, Thomas Pruschke, Juana Moreno, Mark Jarrell By means of large-scale dynamical cluster quantum Monte Carlo simulations, we are able to identify the evolution of the $d$-wave superconducting dome in the hole-dope side of the phase diagram, with next-nearest-neighbor hopping ($t'$), chemical potential and temperature as control parameters. To obtain the superconducting transition temperature $T_c$, we employ two-particle measurements of the pairing susceptibilities. As $t'$ goes from positive to negative values, we find the $d$-wave projected irreducible pairing vertex function is enhanced, and the curvature of its doping dependence changes from convex to concave, which fixes the position of the maximum superconducting temperature at the same filling ($n\approx0.85$) and constraints the dome from precisely following the Lifshitz line. We furthermore decompose the irreducible vertex function into fully irreducible, charge and spin components via the parquet equations, and consistently find that the spin component dominates the pairing vertex function in the doping range where the dome is located. [Preview Abstract] |
Wednesday, March 5, 2014 2:54PM - 3:06PM |
Q52.00003: Charge order instabilities in the t-J model Andrea Allais, Johannes Bauer, Subir Sachdev Motivated by the observation of incommensurate charge order in the pseudogap phase of the cuprates, most notably in a series of recent experiments on YBCO, we explore the occurrence of charge-ordering instabilities in an extended t-J model. We allow for on site and bond ordering, with arbitrary ordering wavevector and a number of possible internal wavefunctions. Our results are obtained by a combination of slave boson mean field theory, dynamical mean field theory and variational Monte Carlo. We find instability towards several possible ordering patterns, depending on the choice of parameters. [Preview Abstract] |
Wednesday, March 5, 2014 3:06PM - 3:18PM |
Q52.00004: Dipolon Theory of High $T_C$ Superconductors--Experimental Proofs of Dipolon Excitations Ram Sharma Owing to the success of the dipolon theory [1,2] in explaining and predicting the properties [1-4] of high $T_C$ superconductors (HTSC) some scientists ask whether the dipolons have been observed. Proofs will be revealed that the dipolons have been observed in variety of experiments not only in superconducting state but also in the normal state. The observed photoemission (PE) spectra (broad peak, dip and sharp peak) and a low energy and two high energy kinks (first predicted [3,4] by dipolon theory and observed later on) ocur due to dipolons [3], inherent in dipolon-theory-deduced five principles [4] of PE. The dipolons have been observed as several optical excitations [1] in HTSC. The observed plasmons and their dispersions are due to [5] the dipolons. The observed but unexplained optical phonons in HTSC are predicted to be a consequence of dipolons. In experiments, no dipolons means no superconductivity.\\[4pt] [1] R. R. Sharma, Phy. Rev. {\bf B 63}, 054506 (2001).\\[0pt] [2] R. R. Sharma, Physica {\bf C 439}, 47 (2006).\\[0pt] [3] R. R. Sharma, Physica {\bf C 468}, 190 (2008).\\[0pt] [4] R. R. Sharma, ``Dipolon Theory..,'' in ``.. Cuprates,'' Ed. K. N. Courtlandt, P. 81-100, Nova Sc, Pub., New York, 2009.\\[0pt] [5] R. R. Sharma, Phys. Rev. {\bf B 54}, 10192 (1996). [Preview Abstract] |
Wednesday, March 5, 2014 3:18PM - 3:30PM |
Q52.00005: Chiral charge order from interlayer tunneling in the hole doped cuprates Akash Maharaj, Srinivas Raghu We show how charge density waves in layered materials can be gyrotropic, {\it i.e.} break spatial inversion and all mirror symmetries. This order is stabilized by coherent interlayer tunneling whose amplitude depends on in-plane momentum. We present mean field calculations which demonstrate the presence of this chiral configuration of charge density waves, and justify these results using a Landau-Ginzburg theory. The implications for recent experiments ({\it e.g.} Kerr, X-ray etc.) in underdoped YBCO are also discussed. [Preview Abstract] |
Wednesday, March 5, 2014 3:30PM - 3:42PM |
Q52.00006: Time reversal symmetry breaking in hole-doped cuprates Andrey Chubukov, Yuxuan Wang We consider charge-density-wave (CDW) instability in weakly hole-doped cuprates. We show that the interaction mediated by spin fluctuations gives rise not only to $d-$wave superconducting pairing but also to (CDW) order with momentum $(\pm Q, 0)$ and $(0,\pm Q)$. We show that this particular order has two components, one symmetric and another anti-symmetric under time reversal. We derive and analyze the corresponding Ginzburg-Landau functional and show that both components appear simultaneously at $T_{CDW}$, i.e., the CDW-ordered state breaks time reversal symmetry. We further show that time-reversal symmetry actually gets broken even before CDW orders develop, as the two CDW components form a (4-fermion) bound state at some $T_{bs} > T_{CDW}$. In between $T_{bs}$ and $T_{CDW}$, time-reversal symmetry is broken, but CDW order does not yet develop. We show that the same result can be obtained by re-expressing the Ginzburg-Landau functional in terms of collective variables and solving saddle-point equations. We discuss experimental consequences of this emerging order. [Preview Abstract] |
Wednesday, March 5, 2014 3:42PM - 3:54PM |
Q52.00007: Evidence for a charge collective mode associated with superconductivity in copper oxides from neutron and x-ray scattering measurements of La$_{2-x}$Sr$_x$CuO$_4$ Seung Ryong Park, T. Fukuda, A.Q.R. Baron, A. Hamann, D. Lamago, L. Pintschovius, M. Fujita, K. Yamada, D. Reznik In superconducting copper oxides some Cu-O bond-stretching phonons around 70meV show anomalous giant softening and broadening of electronic origin and electronic dispersions have large renormalization kinks near the same energy. These observations suggest that phonon broadening originates from quasiparticle excitations across the Fermi surface and the electronic dispersion kinks originate from coupling to anomalous phonons. We measured the phonon anomaly in underdoped (x=0.05) and overdoped (x=0.20,0.25) La$_{2-x}$Sr$_x$CuO$_4$ by inelastic neutron and x-ray scattering with high resolution. Combining these and previously published data, we found that doping-dependence of the magnitude of the giant phonon anomaly is very different from that of the ARPES kink, i.e. the two phenomena are not connected. We show that the phonon anomaly likely originates from novel collective charge excitations as opposed to interactions with electron-hole pairs. Their amplitude follows the superconducting dome so these charge modes may be important for superconductivity. [Preview Abstract] |
Wednesday, March 5, 2014 3:54PM - 4:06PM |
Q52.00008: Fitting of Diverging Effective Mass Obtained by Quantum-Oscillation Measurements in Underdoped YBCO$_{\mathrm{6+x}}$ Systems Hyun-Tak Kim The diverging-effective mass (DEM) in a metallic system is regarded as evidence of strong correlation between fermions in strongly correlated systems. The identity of the DEM still remains to be revealed The effective mass derived from the Brinkman-Rice picture, m*$=$m$_{\mathrm{o}}$/(1-$\rho ^{4})$ [1] where $\rho $ is band filling helps clarify the DEM, m*/m$_{\mathrm{e}}$ analyzed by measurements of quantum oscillation in inhomogeneous underdoped YBCO$_{\mathrm{6+x}}$ systems [2]. As x decreases, m*/m$_{\mathrm{e}}$ increases rapidly like the DEM [2] When it is assumed as the fact that the metal-insulator transition occurs near a critical x$_{\mathrm{c}}\approx $0.45 the data of the DEM [2] is closely well fitted in condition that $\rho =$x$_{\mathrm{c}}$/x increases as x decreases. Its physical meaning is a percolation phenomenon that the extent of the metallic regime is constant and the magnitude of the measurement region, x, increases. It's fitting is performed with m*$=$m$_{\mathrm{e}}$/(1-$\rho^{4})$ where $\rho =$x$_{\mathrm{c}}$/x From the fitting result, we deduce that a correlation strength is greater than 0.95, and conclude that the metal phase of the normal state in YBCO systems is a strongly correlated.\\[4pt] [1] Physica C 341-348(2000)259; e-print arXiv:cond-mat/0110112; Physica C 460--462, 1076 (2007).\\[0pt] [2] PNAS 107 (2010) 6179. [Preview Abstract] |
Wednesday, March 5, 2014 4:06PM - 4:18PM |
Q52.00009: Fermi-surface reconstruction in the cuprate superconductor YBCO via the thermal Hall effect Gael Grissonnanche, Sophie Dufour-Beausejour, Francis Laliberte, Alexis Riopel, Olivier Cyr-Choiniere, Nicolas Doiron-Leyraud, Louis Taillefer, James Day, Brad Ramshaw, Ruixing Liang, Doug Bonn, Walter Hardy, David Graf, Steffen Kramer We recently showed that the thermal conductivity $\kappa_{xx}$ can be used to directly measure the upper critical field H$_{c2}$ in cuprate superconductors [1]. Here we show that the thermal Hall conductivity $\kappa _{xy}$ can be used to probe the nature of the carriers in these materials. We present a study of $\kappa_{xy}$ in YBCO at a doping p $=$ 0.11, as a function of magnetic field up to 35 T down to low temperature. The fact that $\kappa_{xy}$ is negative above H$_{c2} \quad =$ 24 T confirms the presence of an electron-like pocket in the normal-state Fermi surface [2], the result of a reconstruction caused by the emergence of charge order at low temperature [3]. We show how the Fermi-surface reconstruction evolves as a function of field and temperature. [1] G. Grissonnanche \textit{et al.}, arXiv:1303.3856 (2013). [2] D. LeBoeuf \textit{et al}., Nature 450, 533 (2007). [3] F. Lalibert\'{e} \textit{et al}., Nature Communications 2, 432 (2011). [Preview Abstract] |
Wednesday, March 5, 2014 4:18PM - 4:30PM |
Q52.00010: A new quantum oscillation frequency in the thermoelectric response of YBa2Cu3Oy Nicolas Doiron-Leyraud, Samuel Rene de Cotret, Francis Laliberte, Louis Taillefer, Brad Ramshaw, Ruixing Liang, Doug Bonn, Walter Hardy The Seebeck and Nernst coefficients of the cuprate superconductor YBa2Cu3Oy were measured in a high-quality single crystal with doping p = 0.11, as a function of magnetic field up to 45 T at low temperatures. Giant quantum oscillations are observed in both thermoelectric coefficients. The dominant frequency Fa = 530 T is in agreement with previously observed oscillations in transport, specific heat, and magnetization, attributed to a closed electron Fermi surface. The Seebeck effect reveals an additional frequency Fb = 95 T [1], with a low effective mass [2]. We propose that this new frequency arises from a hitherto undetected closed hole-like Fermi surface. This can explain the variation with magnetic field of several transport properties, such as the Seebeck, Hall [3], and thermal Hall effects, as well as the doping dependence of the normal-state Seebeck effect at low temperature [4], which is inconsistent with a lone electron pocket. Work performed at the NHMFL Tallahassee. [1] N. Doiron-Leyraud et al., preprint. [2] S. Badoux et al., preprint. [3] D. LeBoeuf et al., Phys. Rev. B 83, 054056 (2011). [4] F. Laliberte et al., Nat. Commun. 2, 432 (2011). [Preview Abstract] |
Wednesday, March 5, 2014 4:30PM - 4:42PM |
Q52.00011: Linear magnetic field dependence of the specific heat in underdoped YBCO Jonathon Kemper, Oskar Vafek, Scott Riggs, Jon Betts, Fedor Balakirev, Albert Migliori, Ruixing Liang, Walter Hardy, Doug Bonn, Gregory Boebinger We report the observation of two distinct regimes in the field dependence of the low temperature electronic heat capacity (C) of YBa$_2$Cu$_3$O$_{6.47}$. Measurements were performed in applied magnetic fields ($H$) up to 34.5~T and at temperatures between 1 and 8 K. Below 10 T we observe C$\sim H^{1/2}$ attributable to a d-wave superconducting gap. Above 10 T, C approaches a nearly linear-in-field form. All behavior is clearly observable well below the field-induced resistive transition, and thus, likely closely tied to the nodes in the gap. We rule out the suppression of the superconducting gap by the magnetic field as a possible explanation through a comparison with specific heat data from other dopingsof underdoped YBCO. [Preview Abstract] |
Wednesday, March 5, 2014 4:42PM - 4:54PM |
Q52.00012: The structure of oxygen-annealed La$_{1.9}$Ca$_{1.1}$Cu$_{2}$O$_{6}$ superconductor Hefei Hu, Yimei Zhu, Ruidan Zhong, John Schneeloch, Tiansheng Liu, Genda Gu, John Tranquada, John Hill, Simon Billinge Effect of annealing under high oxygen pressure on La$_{1.9}$Ca$_{1.1}$Cu$_{2}$O$_{6}$ (2126) is studied and structure change at the nanometer scale is investigated by using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The as-grown single crystal is non-superconducting, which is thought to be due to oxygen deficiency. With annealing under a high oxygen pressure, superconductivity is induced with T$_{\mathrm{c}}$ $\sim$ 53 K. While the as-grown 2126 shows homogenous structure at a large scale, after oxygen annealing, the sample develops a secondary phase La$_{\mathrm{2-x}}$Ca$_{\mathrm{x}}$CuO$_{4}$(214) at nanometer scale, which is evidenced by electron diffraction patterns together with EELS analysis. The content of 214 phase is estimated to be around 20{\%} based on the analysis of scanning TEM images. Magnetization measurements indicate that the 214 phase is also superconducting. Chemical change of the remaining 2126 phase after oxygen annealing will also be discussed. [Preview Abstract] |
Wednesday, March 5, 2014 4:54PM - 5:06PM |
Q52.00013: Magnetic Penetration Depth in Tl-2201: Disentangling the In- and Out-of-plane Components S. Mahyad Aghigh, Jordan Baglo, James Day, Darren Peets, Pinder Dosanjh, Ruixing Liang, Walter Hardy, Doug Bonn Investigation of Tl$_{2}$Ba$_{2}$CuO$_{6+\delta}$ (Tl-2201) properties is important as it provides access to the overdoped side of the superconducting dome in a material with relatively low quasiparticle scattering rates. As one of the most fundamental characteristics of a superconductor, we have measured the magnetic penetration depth, $\lambda$(T), for a single crystal of Tl-2201 with T$_{c}$= 43 K using a loop-gap cavity perturbation technique well established by our group. Taking advantage of the tetragonal structure of this cuprate, as well as the existing measurements of the absolute value of the penetration depth at zero temperature, the in- and out-of-plane components, $\lambda$$_{ab}$(T) and $\lambda$$_{c}$(T) have been determined. In this talk I will describe the measurement technique, the disentangling procedure, as well as the degree of reliability of the results. [Preview Abstract] |
Wednesday, March 5, 2014 5:06PM - 5:18PM |
Q52.00014: Field-Dependent Specific Heat Study of Chain Superconductivity in YBa$_2$Cu$_4$O$_8$ Philip Walmsley, Antony Carrington A unique property of the Y-based cuprate superconductors is the presence of conducting quasi-1-D CuO chains in addition to the CuO2 planes in which superconductivity is thought to originate. The nature of the superconducting interactions in the chains remains a matter of debate. YBa$_2$Cu$_3$O$_{7-\delta}$ (Y123) has a single b-axis CuO chain per unit cell whereas its stoichiometric relative YBa$_2$Cu$_4$O$_8$ (Y124) has two filled chains per unit. Previously, it has been observed that at low temperature there is an anomalous increase in the superfluid density along the b and c directions in Y124 which does not occur in Y123. The response along the a direction in Y124 is linear as expected for a d-wave nodal gap. This anomalous increase in Y124 is likely caused by proximity coupling to the planes. In this work we present a study of the field dependent specific heat in Y124. The field induced changes in the electronic specific heat due to the Volovik effect are used to deduce the field scale which quenches chain superconductivity. [Preview Abstract] |
Wednesday, March 5, 2014 5:18PM - 5:30PM |
Q52.00015: Charge and magnetic excitations in hole- and electron-doped infinite layer cuprate superconductors G. Dellea, L. Maritato, A. Galdi, P. Orgiani, D.G. Schlom, D. Di Castro, A. Tebano, G. Balestrino, C. Aruta, M. Moretti Sala, N.B. Brookes, C.J. Jia, B. Moritz, T.P. Devereaux, M. Minola, C. Mazzoli, L. Braicovich, G. Ghiringhelli Infinite layers (IL) present the simplest crystallographic structure among layered cuprates. Here we present $Cu-L_3$ resonant inelastic x-ray scattering (RIXS) measurements on insulating and superconducting IL systems. In particular, we compare spectra for the two possible doping mechanisms, n- and p-type. $(CaCuO_2)_m/(SrTiO_3)_n$ superlattices are characterized by hole doping,\footnote{D. Di Castro et al., Phys. Rev. B 86, 134524(2012).} while $Sr_{1-x}La_xCuO_2$ presents electron doping.\footnote{L. Maritato et al., J. Appl. Phys. 113, 053911(2013).} Beside several analogies, the two systems show noticeable differences in evolution with doping level of the charge excitation continuum and of the magnetic peak intensity and damping. These trends can be found also in the corresponding theoretical calculations, in which the spin-spin correlation function is determined using a single band Hubbard model plus 2p core level with spin-orbit coupling.\footnote{C. J. Jia et al., http://arxiv.org/abs/1308.3717(2013).} [Preview Abstract] |
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