Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Y52: Competing Orders and Phase Diagrams in Copper-oxide Superconductors |
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Sponsoring Units: DCMP Chair: Hai-Hu Wen, Nanjing University Room: Mile High Ballroom 1F |
Friday, March 7, 2014 8:00AM - 8:12AM |
Y52.00001: Superconducting fluctuations and Fermi surface reconstruction in underdoped cuprates Shizhong Zhang, Sumilan Banerjee, Mohit Randeria Recent observation of quantum oscillations in underdoped Hg1201 has indicated that the small Fermi surface (FS) is an intrinsic property of the Copper-oxide plane [1]. The emergence of small FS requires significant FS reconstruction in a magnetic field $H$. Experiments have found signatures of both uni- and bi-directional charge orders that can lead to such FS reconstruction. For the bi-directional charge order, however, a large, and possibly unrealistic, value of charge ordering potential is necessary to compare favourably with experiments. We show that by taking into account static superconducting (SC) fluctuations the required charge ordering potential can be dramatically reduced, while reconciling the observed $\sqrt{H}$ dependence of the specific heat. We comment on why dissipation leads to static, as opposed to dynamical, SC fluctuations [2] at low-temperature and high field. [1] N. Barisic et al., Nature Physics, doi:10.1038/nphys2792 (2013). [2] S. Banerjee, S. Zhang and M. Randeria, Nature Comm. 4, 1700 (2013). [Preview Abstract] |
Friday, March 7, 2014 8:12AM - 8:24AM |
Y52.00002: Evidence for Competing Order in Underdoped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ from Break Junction Tunneling Spectroscopy John Zasadzinski, Nicholas Groll, Chaoyue Cao, Mike Hinton, Thomas Proslier, Thomas Lemberger Superconductor-insulator-superconductor (SIS) break junction tunneling measurements of the low-temperature, single-electron gap parameter, $\Delta $, are reported on heavily underdoped thin films of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ (Bi2212). This extends previous, doping-dependent studies on bulk single crystals and the combined data reveal that for hole concentrations, $p$ \textless 0.11 there is an abrupt change in slope of $\Delta (p)$ along with the observation of extraordinarily large single-electron energy gaps ($\Delta $ $\sim$ 115 meV-135 meV). This underdoped region displays a corresponding drop in the superfluid density and distinctive changes in the shape of the electronic density of states (DOS). The shape of $\Delta $(T) near Tc (as measured by the loss of Josephson current) is inconsistent with single gap scenarios. The combined results signal that a competing order has emerged. The underdoped $\Delta $ values are close to the antiferromagnetic exchange energy, J, and the overall trends indicate that the quasiparticle gap in the DOS has evolved from primarily superconducting to primarily magnetic character. These results may be relevant for pseudogap phenomena in underdoped cuprates. [Preview Abstract] |
Friday, March 7, 2014 8:24AM - 8:36AM |
Y52.00003: Charge ordering and Fermi-arc instability in underdoped cuprates Riccardo Comin, George Sawatzky, Andrea Damascelli, Alex Frano, Bernhard Keimer, Michael Yee, Jennifer Hoffman, Enrico Schierle, Eugen Weshcke, Ronny Sutarto, Feizhou He, Yoshiyuki Yoshida, Hiroshi Eisaki The underdoped cuprate pseudogap, and related ``Fermi-arc'' phenomenology, is one of the most remarkable phenomena in strongly correlated-electron systems. Despite evidence for various forms of electronic instabilities, a direct link to an underlying ordered phase is still mysterious. Here we report a combined investigation of one single cuprate family by real- and momentum-space, and surface and bulk probes - resonant X-ray scattering (REXS), scanning-tunnelling microscopy (STM), and angle-resolved photoemission spectroscopy (ARPES)--which individually had a profound impact on the understanding of high-Tc cuprate superconductors, but have so-far been analyzed and interpreted within different phenomenological frameworks--and never for the very same compound. By bringing together these techniques, and with the aid of calculations of the electronic response, we establish a precise, quantitative correspondence between the Fermi arc phenomenon seen in ARPES and charge ordering as observed by REXS and STM. These converging findings suggest the existence of a universal charge-ordered state in underdoped cuprates and reveal its connection to the pseudogap phase and related fermiology. [Preview Abstract] |
Friday, March 7, 2014 8:36AM - 8:48AM |
Y52.00004: Quantum oscillations in a non-Fermi liquid cuprate pseudogap state Yan He, Peter Scherpelz, K. Levin We analyze the properties of quantum oscillations in a pseudogap (ie, non-Fermi liquid) state and, thereby, address recent experiments in the high-field regime of cuprate superconductors. We use a Gor'kov-based, Landau level model of the pseudogap state appropriate for very high fields, and find that a gapped state will generally display oscillations in this regime. This is due both to d-wave pairing and to the presence of gap inhomogeneities, reflecting a blurred vortex state [1]. We calculate the temperature dependence of these oscillations and show that for realistic cuprate parameters, these systems display behavior essentially indistinguishable from that of Fermi liquids [2]. [1] P. Scherpelz, D. Wulin, K. Levin and A. Rajagopal, PRA 87 063602 (2013). [2] P. Scherpelz, Y. He and K. Levin, arXiv:1310.2645. [Preview Abstract] |
Friday, March 7, 2014 8:48AM - 9:00AM |
Y52.00005: NMR investigation of charge order in YBa$_{2}$Cu$_{3}$O$_{\mathrm{y}}$ in high magnetic fields M. Hirata, H. Mayaffre, S. Kraemer, M. Horvatic, C. Berthier, MH. Julien, P.L. Kuhns, A.P. Reyes, R. Liang, W.N. Hardy, D.A. Bonn Recent observation of the charge-density-wave (CDW) order or CDW fluctuations in underdoped YBa$_{2}$Cu$_{3}$O$_{\mathrm{y}}$ (YBCO) marks an important step in high-$T_{\mathrm{C}}$ research because it lends support to the idea that charge ordering is a generic instability of the pseudogap state. However, the relevance of these results to the understanding of superconductivity remains unclear. An important question is how charge ordering evolves as a function of doping across the phase diagram. Here, we expand our previous work [1] and report high-field $^{17}$O NMR evidence of charge order in YBCO with doping level $p = $0.09 and $p = $0.13. We discuss the evolution of the temperature and field scales characterizing the CDW transition.\\[4pt] [1] T. Wu \textit{et al.} \textit{Nat.} \textit{Commun.}\textbf{4}, 2113 (2013). [Preview Abstract] |
Friday, March 7, 2014 9:00AM - 9:12AM |
Y52.00006: Doping Dependence of Spin and Phonon Hybridization in $La_{2-x}Ba_{x}CuO_{4}$ Jerod Wagman, J.P. Carlo, G. Van Gastel, M.B. Stone, J.L. Niedziela, G.E. Granroth, A.I. Koleshnikov, L. DeBeer-Schmitt, A.T. Savici, Z. Yamani, Z. Tun, Y. Zhao, A.B. Kallin, E. Mazurek, H.A. Dabkowska, B.D. Gaulin 'Hour-glass' shaped dispersions of antiferromagnetic (AF) spin fluctuations are a robust feature common to many high temperature superconductors. In La-214 cuprates, these phenomena are well known to display a strong dependence on the concentration of holes that are introduced into the copper oxide planes by doping. Here, we present a series of neutron scattering measurements on single crystals of $La_{2-x}Ba_{x}CuO_{4}$ (LBCO), with $0 \leq x \leq 0.095$. This is a doping range that spans the phase diagram from insulating three dimensional commensurate AF to superconducting two dimensional incommensurate AF. Our measurements comprehensively map out the evolution of the spin excitations below $\sim$ 40 meV. In particular, we focus on the rich structures that arise at the many crossings of the highly dispersive spin excitations with the many phonon eigenvectors in this system. The nature of these structures are suggestive of spin-phonon hybridized modes, which seem to pervade the phase diagram of LBCO. [Preview Abstract] |
Friday, March 7, 2014 9:12AM - 9:24AM |
Y52.00007: Competing charge, spin, and superconducting orders in underdoped YBCO M. Huecker, E. Blackburn, D.A. Bonn, J. Chang, N.B. Christensen, E.M. Forgan, O. Gutowski, W.N. Hardy, S.M. Hayden, A.T. Holmes, R. Liang, D.S. Robinson, U. Ruett, M. v. Zimmermann High energy X-ray diffraction experiments on $\rm YBa_2Cu_3O_{y}$ were performed to explore the doping evolution of the recently discovered charge density wave (CDW) phase. The results show that the CDW phase exists at least for charge carrier concentrations of $0.078 < p < 0.132$. Hence, the lower bound is located in vicinity of the quantum critical point to spin density wave order. For all dopings CDW order sets in in the normal state, but is partially suppressed upon cooling below $T_c$. This clearly suggests a competition between the two states. The incommensurability of the CDW order decreases approximately linear with the hole concentration, which is in contrast to the increase observed for stripe order in La-based cuprates. A detailed comparison with the charge stripe order in $\rm La_{2- \it x}Ba_{\it x}CuO_{4}$ is presented. [Preview Abstract] |
Friday, March 7, 2014 9:24AM - 9:36AM |
Y52.00008: Microscopic investigation of the dopant oxygen distribution using $^{199}$Hg NMR in the high temperature superconductor HgBa$_2$CuO$_{4+\delta}$ Yizhou Xin, A.M. Mounce, Jeongseop Lee, Sangwon Oh, W.P. Halperin, A.P. Reyes, P.L. Kuhns, M.K. Chan, C. Dorrow, L. Ji, D. Xia, X. Zhao, M. Greven In the high temperature superconductor HgBa$_2$CuO$_{4+\delta}$, it has been determined that the dopant oxygen O$_\delta$ resides in the Hg-plane [1]. The systematic development of the $^{199}$Hg NMR spectrum as a function of O$_\delta$ content is presented. For high O$_\delta$, 4 different resonance peaks are observed. Three of the peaks follow a binomial distribution and correspond to 0, 1, and 2 O$_\delta$ nearest neighbors. The fourth peak persists down to low doping and may be indicative of a Hg vacancy nearest neighbor. This work was supported by the DOE BES under grants No. DE-FG02-05ER46248 and No. DE-SC0006858 and the NHMFL through the NSF and State of Florida. \\[4pt] [1] J. G. Correia \textit{et}. PRB \textbf{64}, 11769 (2000). [Preview Abstract] |
Friday, March 7, 2014 9:36AM - 9:48AM |
Y52.00009: Antiferromagnetic fluctuations and the pseudogap in the moderately underdoped high-temperature superconductor HgBa$_{2}$CuO$_{4+\delta}$ Mun Chan, C. Dorow, M. Veit, Y. Tang, Y. Ge, M. Greven, L. Mangin-Thro, Y. Sidis, P. Bourges, X. Zhao, P. Steffens, A. Christianson, D.L. Abernathy, J.T. Park The two most salient features of the magnetic excitation spectrum of the cuprate superconductors are the hourglass dispersion and the resonance mode. Our neutron scattering measurements demonstrate that both features are either absent or significantly weakened in moderately underdoped HgBa$_{2}$CuO$_{4+\delta}$ (Hg1201; T$_{\mathrm{c}}\approx $71 K; p$\approx $0.09). The magnetic spectrum is gapped below 27 meV, and is commensurate with the antiferromagnetic wave-vector above the gap. Above 60 meV, it disperses upward into a ring of scattering. This Y-shaped spectrum is reminiscent of that observed in the pseudogap of YBa$_{2}$Cu$_{3}$O$_{\mathrm{6+y}}$ (YBCO). Unlike YBCO, the antiferromagnetic fluctuations of Hg1201 are rather impervious to the onset of superconductivity at T$_{\mathrm{c}}$. Instead, a large peak in the susceptibility at about 53 meV onsets at the much higher pseudogap temperature T*. The dramatic increase of magnetic scattering below T* reveals a strong connection between magnetism and the pseudogap. The results for this structurally simple compound present a challenge for theoretical explanations that have focused largely on the hourglass dispersion and the resonance. [Preview Abstract] |
Friday, March 7, 2014 9:48AM - 10:00AM |
Y52.00010: Antiferromagnetic fluctuations in the very underdoped high-temperature superconductor HgBa$_2$CuO$_{4+\delta}$ M. Veit, M.K. Chan, C. Dorow, T. Yang, G. Yang, M. Greven, L. Mangin-Thro, Y. Sidis, P. Bourges, X. Zhao, P. Steffens, A. Christianson, D.L. Abernathy, J.T. Park We report inelastic neutron scattering measurements of magnetic fluctuations over a large energy and momentum range in the high-temperature cuprate superconductor HgBa$_2$CuO$_{4+\delta}$ (Hg1201) at two low doping levels (UD45: T$\mathrm{_c}$$\approx$45K, p$\approx$0.058; UD55: T$\mathrm{_c}$$\approx$55K, p$\approx$0.063). In both samples, the ``hourglass'' dispersion, thought to be universal among the cuprates, is not observed. Instead, the antiferromagnetic spectrum is commensurate just above the magnetic gap ($\sim$10 meV in both samples) and disperses outwards into a ring of scattering above $\sim$50 meV. The magnetic resonance is prominently observed in UD45 (at $\sim$20meV), but is small or non-existent in higher-doped UD55. This result runs counter to the heretofore accepted notion that the resonance is most prominent in the compounds with the highest optimal T$\mathrm{_c}$. Additionally, we find that the previously reported Ising-like dispersionless excitations in optimal and moderately underdoped Hg1201 is no longer observed in UD45. We conclude that there exists a crossover near p$\sim$0.06 between two distinct regimes. [Preview Abstract] |
Friday, March 7, 2014 10:00AM - 10:12AM |
Y52.00011: Cuprate Pseudogap loop currents, observed by muon probing C. Boekema, P. Sakkaris, A. Love, M. Tran, F. Owens, H. Sio, W.K. Dawson Pertaining to Varma's loop currents (LpI) in the cuprate pseudogap phase, [1] we have observed [2] in zero field weak $\mu $SR LpI signals for two GdBCO samples above and below their T$_{\mathrm{c}}$'s of 81 K (underdoped) and 93 K (optimal doped). The measured fields are about the predicted 100 Oe. The question is, can the muon probe these fields. Shekhter \textit{et al} [3] found theoretically that positive muons destroy Varma's loop currents. In contrast, by analyzing transverse field $\mu $SR GdBCO data using MaxEnt, [4] we confirm the muon probes in \textit{insulating} regions near the BaO layers (Balmer sites) and CuO chain layers (Lin sites). [5] Thus, muons do \textit{not} destroy Varma's loop currents in the CuO$_{\mathrm{2}}$ planes, and can precisely probe their fields. In conclusion, well below RT we have detected LpI-$\mu $SR signals for GdBCO with a probability of occurrence of $\sim$ 65 {\%}. [2] Our ME$\mu $SR optimal doped GdBCO results indicate, the QCP in the cuprate phase diagram is located near the endpoint of the superconductivity dome. A magnetic origin for cuprate superconductivity is plausible. Research is supported by RSCA-SJSU and AFC San Jose. [1] CM Varma PRL \textbf{83} (1999) 3538; ME Simon, CM Varma PRL \textbf{89} (2002) 247003. [2] C Boekema \textit{et al,} 493 (2013) 136; T Songatikamas \textit{et al,} J Supercond {\&} Nov Magn \textbf{23} (2010) 793. [3] A Shekhter \textit{et al,} PRL \textbf{101} (2008) 227004. [4] C Boekema, MC Browne, AIP Conf Proc {\#}1073 (2008) 260; JC Lee \textit{et al}, J Appl Phys \textbf{95} (2004) 6906. [5] WK Dawson \textit{et al}, J Appl Phys \textbf{64} (1988) 5809; Hpf Interactions \textbf{63} (1990) 219. [Preview Abstract] |
Friday, March 7, 2014 10:12AM - 10:24AM |
Y52.00012: Persistent spin excitations in doped cuprates revealed by resonant inelastic light scattering C.J. Jia, E.A. Nowadnick, K. Wohlfeld, Y.F. Kung, C.-C. Chen, S. Johnston, T. Tohyama, B. Moritz, T.P. Devereaux How coherent quasiparticles emerge upon doping a quantum antiferromagnet is a key question in correlated materials, underlying an understanding of the cuprate phase diagram. Recent resonant inelastic x-ray scattering (RIXS) experiments in hole-doped cuprates measured high energy collective spin excitations that persist well into the overdoped regime and bear a striking resemblance to those found in the parent compound, challenging the perception that spin excitations should weaken with doping and have a diminishing effect on superconductivity. We show that RIXS at the Cu L3-edge indeed provides access to the spin dynamical structure factor once one considers the full influence of light polarization. Further we demonstrate that high-energy spin excitations do not correlate with the doping dependence of Tc, while low-energy excitations depend sensitively on doping and show a crossover from antiferromagnetic to ferromagnetic correlations. This suggests that although high-energy spin excitations persist well into the overdoped regime, they are marginal to pairing in cuprate superconductors. \\[4pt] [1] arXiv:1308.3717 [cond-mat.str-el] [Preview Abstract] |
Friday, March 7, 2014 10:24AM - 10:36AM |
Y52.00013: Broken symmetry in the cuprate phase diagram: Oxygen engineer- ing in electron doped cuprate superconductors and its impact on competing orders Yoshiharu Krockenberger, Hiroshi Irie, Osamu Matsumoto, Keitaro Yamagami, Masaya Mitsuhashi, Akio Tsukada, Michio Naito, Hideki Yamamoto In high temperature superconductors, superconductivity is induced by chemical doping. This relation is one of the most studied in solid state physics since superconducting transition temperatures beyond the boiling point of nitrogen have been realized. So far, only doping stabilizes the superconducting ground state by destruction of the long-range antiferromagnetic order of the 3$d^{9}$ Cu$^{2+}$ moments and alternatives for an increase of the superconducting transition temperature are in great demand. We show that the conventional mechanism of doping for the induction of superconductivity does not apply to a class of materials characterized by square-planar coordination of copper. We prepared thin films of Pr$_{2}$CuO$_{4}$, a strongly correlated material with a magnetically driven insulating ground state - and show that annealing drives the localized charge carriers into motion, leading to the emergence of a superconducting ground state. This non-local switching of the electronic states is achieved by the application of an elaborate annealing method. The superconducting transition appears at temperatures higher than that induced by doping. Our results demonstrate a conceptually new tuning parameter for the induction of superconductivity, extending the concept of doping control. [Preview Abstract] |
Friday, March 7, 2014 10:36AM - 10:48AM |
Y52.00014: Evidence for Intertwining of Superconductivity and Antiferromagnetism in a Cuprate John Tranquada, Zhijun Xu, C. Stock, S.X. Chi, A.I. Kolesnikov, G.Y. Xu, G.D. Gu We have used inelastic neutron scattering to measure the low-energy, incommensurate antiferromagnetic spin excitations both above and below the superconducting transition temperature ($T_c = 32$~K) of La$_{1.905}$Ba$_{0.095}$CuO$_4$ [1]. While the magnetic excitations in optimally-doped cuprates typically show the development of a spin gap and magnetic resonance below $T_c$, our sample shows no such effect. Instead strong, gapless spin excitations coexist with bulk superconductivity. To understand this, we note that previous transport measurements have shown that the superconducting layers are decoupled by a magnetic field applied along the $c$-axis, resulting in a state with frustrated interlayer Josephson coupling, similar to LBCO with $x=1/8$, where it has been proposed that pair-density-wave superconductivity occurs. This suggests that, in a similar fashion, the spatially modulated antiferromagnetic correlations (which we see directly in the $x=0.095$ sample) are intertwined with a spatially modulated superconducting pair wave function. \\[4pt] [1] Z. J. Xu {\it et al.}, arXiv:1309.2718. [Preview Abstract] |
Friday, March 7, 2014 10:48AM - 11:00AM |
Y52.00015: Fermi-arcs from angular fluctuations of a multi-component order parameter Debanjan Chowdhury, Subir Sachdev Angle resolved photoemission experiments on the underdoped cuprates have seen evidence for highly unusual gapless Fermi-arcs. They appear as disconnected surfaces above the superconducting transition temperature and below an onset temperature scale, which is the onset of the pseudogap as has been seen in a large number of probes. Over the past few years a lot of insight has been gained into the nature of the mysterious pseudogap state with the discovery of a fluctuating charge-ordered state with a finite correlation length. It has recently been suggested [1] that the pseudogap regime is described by the angular fluctuations of a multi-component order parameter. In this work, we study the effect of these fluctuations on the spectral function of the underlying fermions and show that the arcs occur naturally in the presence of fluctuating charge-order and superconducting correlations. We analyze the relative importance of these fluctuations as a function of temperature and make connections with recent photoemission experiments. [1] L. Hayward, D. Hawthorn, R. Melko and S. Sachdev, arXiv:1309.6639. [Preview Abstract] |
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