Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session D11: Coexisting Orders In Underdoped Cuprates |
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Sponsoring Units: DMP Chair: Vivek Mishra, Argonne National Laboratory Room: 007B |
Monday, March 2, 2015 2:30PM - 2:42PM |
D11.00001: Combinatorial Deposition of La$_{2-x}$Ba$_x$CuO$_4$ Thin Films Across the x=1/8 Anomaly Justin Lane, Adam Weis, Azton Wells, So Ra Chung, Pathikumar Sellappan, Waltraud Kriven, Dale Van Harlingen La$_{2-x}$Ba$_x$CuO$_4$ (LBCO) has an unusual phase diagram that includes a charge stripe phase in proximity to suppressed superconductivity near x=1/8 doping. We will present recent improvements to LBCO thin films grown by pulsed laser deposition from high-quality metalorganic-synthesized ceramics. Using a combination of Ba-poor and Ba-rich deposition sources and a combinatorial pulsed laser deposition technique, we are able to tune doping of LBCO and measure the superconducting transition temperature as a function of doping. We correlate the spatial offset between deposition plume and substrate with the resultant sample's dopant distribution. Characterization of these films by a high-throughput resistance technique and use of the samples in ongoing experiments will be discussed. [Preview Abstract] |
Monday, March 2, 2015 2:42PM - 2:54PM |
D11.00002: ABSTRACT WITHDRAWN |
Monday, March 2, 2015 2:54PM - 3:06PM |
D11.00003: In-plane resistivity anisotropy in underdoped cuprates due to scattering by charge and spin fluctuations Michael Sch\"utt, Rafael M. Fernandes The existence of strong in-plane electronic anisotropies in underdoped cuprates has been reported by a variety of experimental probes, such as transport measurements, scanning tunneling microscopy, and x-ray and neutron scattering. Understanding the origin of these anisotropies and their interplay is fundamental to elucidate the role played by electronic nematicity in the phase diagram of the cuprates. Here we employ a Boltzmann equation approach to investigate the resistivity anisotropy due to scattering by anisotropic spin and charge fluctuations. We show that while spin fluctuations give rise to larger resistivity along the $a$ direction, charge fluctuations promote larger resistivity along the $b$ direction. Because anisotropic charge and spin fluctuations compete, these behaviors give rise to a particular dependence of the resistivity anisotropy with doping, which is consistent with transport experiments performed in YBa$_{2}$Cu$_{3}$O$_{7}$. We discuss the important role played by the CuO chains in YBCO to select the observed type of nematic domains, and propose transport measurements in strained HgBa$_{2}$CuO$_{4}$ and Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ to shed light on the interplay between anisotropic fluctuations and anisotropic resistivity. [Preview Abstract] |
Monday, March 2, 2015 3:06PM - 3:18PM |
D11.00004: Superconductivity and charge order in 1/8 doped LBCO probed by proton-induced disorder Maxime Leroux, Vivek Mishra, Helmut Claus, Ulrich Welp, Asghar Kayani, Zahirul Islam, Genda Gu, Wai-Kwong Kwok The question of how charge order coexists or competes with superconductivity is a subject of intense and active research, as its resolution could be key in explaining the origin of superconductivity in cuprates superconductors. Here we report that the T$_{\mathrm{c}}$ of La$_{\mathrm{1.875}}$Ba$_{\mathrm{0.125}}$CuO$_{\mathrm{4}}$ (LBCO) increases by up to 50{\%} after proton irradiation. At high enough energy, proton irradiation creates a uniform density of small nm-sized amorphous clusters and point defects, which results in a uniform and isotropic 3D distribution of defects [1]. However, it is well known that non-magnetic defects are pair-breaking for d-wave superconductivity, and should therefore reduce Tc. We speculate that proton-induced disorder directly affects the balance between competing density wave and superconducting ground states. [1] Jia, Y. et al. Appl. Phys. Lett. 103, 122601 (2013); M. A. Kirk, Cryogenics 33, 235 (1993), M. A. Kirk, Y. Yan, Micron 30, 507 (1999). This work is supported by the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. D.O.E., Office of Science, Office of Basic Energy Sciences and by the D.O.E, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Monday, March 2, 2015 3:18PM - 3:30PM |
D11.00005: $^{17}$O NMR Study of Under-doped Single Crystals of the High Temperature Superconducting Compound Hg1201 W.P. Halperin, Jeongseop A. Lee, Yizhou Xin, A.M. Mounce, A.P. Reyes, P.L. Kuhns We present measurements of $^{17}$O high field NMR on oxygen isotope exchanged under-doped single crystals of the single layer superconductor,$^1$ HgBa$_{2}$CuO$_{4+\delta}$, a compound having a known tetragonal lattice. Our $^{17}$O data for two under-doped samples (T${_c}$ of 87\,K and 79\,K) indicates that there are two inequivalent oxygen planar sites based on measurements of upper and lower quadrupolar satellites. Spectra were taken with 4 K $< T <$ 400 K and 6 T $< H <$ 30 T with a goniometer to precisely orient crystals relative to the magnetic field. We found an asymmetry in the line shape between the upper and lower satellites that cannot be accounted for by a model with a single planar oxygen site. Comparison will be made to earlier work$^2$ on under-doped YBa${_2}$Cu${_3}$O$_{7-y}$. \noindent [1] A.M. Mounce, {\it et al.}, Phys. Rev. Lett. {\bf 111}, 187003 (2013).\\ \noindent [2] T. Wu {\it et al.} Nature Comm. {\bf 4}, 2113 (2013). [Preview Abstract] |
Monday, March 2, 2015 3:30PM - 3:42PM |
D11.00006: Enhanced Fluctuation/Inhomogeneity Effects Near The Superconductor-Insulator Transition in Severely Underdoped 2D Films of Ca$_{0.3}$Y$_{0.7}$Ba$_2$Cu$_3$O$_{7-\delta}$ Stanley Steers, Thomas Lemberger It has been shown that the superconductor-insulator transition in two-dimensional, severely underdoped films of Ca-doped YBCO is accompanied by a linear scaling between the zero temperature superfluid density $n_s(T=0) $ and the temperature for the unbinding of thermally excited vortex pairs, $T_{2D}$.\footnote{I. Hetel, T.R. Lemberger and M. Randeria, Nature Phys {\textbf 3}, 700 (2007).} We present results from resistivity and magnetic screening studies on 2D Ca-YBCO showing a linear relationship between the width of tails in the resistive transition and $T_{2D}$. These tails show a significant suppression of resistivity and can extend down for tens of Kelvins before the films exhibit magnetic screening. We examine this relationship in light of a possible enhancement of inhomogeneous effects in the vicinity of the superconductor-insulator transition with underdoping. [Preview Abstract] |
Monday, March 2, 2015 3:42PM - 3:54PM |
D11.00007: Simultaneous AFM-STM on BSCCO Drew Edelberg, Mihir Bhaskar, Pinshane Huang, Abhay Pasupahy Scanning tunneling microscopy is limited by its inability to resolve the difference between local electronic structure and surface topography since the tunneling current is a convolution of electronic density and tip height. Such a limitation is especially problematic in studying strongly correlated materials on the verge of the insulating state that exhibit strong local variations in the density of electronic states. Recently, non-contact AFM [1] has emerged as a force-based technique capable of providing atomic resolution height information above a surface, allowing us to decouple electronic features from atomic structure. In this work, we describe the use of nc-AFM to study the surface of the high-temperature superconductor BSCCO with atomic resolution in the superconductor and pseudogap phases. By mounting an STM tip to the nc-AFM probe, we measure the true position-dependent density of states independent of tunneling junction normalization. We will demonstrate that performing dI/dV spectroscopy at constant force feedback is a powerful tool that provides additional physical information about local charge in a correlated material. [1] F. J. Giessibl et al., Nanotechnology \textbf{15}, S79-S86 (2004). [Preview Abstract] |
Monday, March 2, 2015 3:54PM - 4:06PM |
D11.00008: Nonlinear Hall effect and Shubnikov-de Haas quantum oscillations in thin films of the electron doped superconductor Pr2CuO4 Nicholas Breznay, Nityan Nair, James Analytis, Zengwei Zhu, Kimberly Modic, Ross McDonald, Yoshiharu Krockenberger Recent quantum oscillation studies in cuprate superconductors have allowed for considerable progress in understanding their Fermi surface topography. However, important questions remain about the influence of quantum criticality and competing orders, as well as the universality of these results; in particular quantum oscillation studies to date have been largely confined to a limited range of hole-doped bulk crystal systems. We have observed a field nonlinear Hall effect in superconducting thin films of the cuprate Pr$_2$CuO$_4$, and studied the temperature and magnetic field dependence of this behavior. The Hall effect data are consistent with a simple two-band transport model in this material, and we will interpret them in light of recently observed Shubnikov-de Haas quantum oscillations in these films. [Preview Abstract] |
Monday, March 2, 2015 4:06PM - 4:18PM |
D11.00009: Near-Room Temperature Studies of the Pseudogap Phase of Underdoped Bi-2212 Ling Fu, Aaron Kraft, Genda Gu, Michael Boyer Most scanning tunneling microscopy (STM) studies on significantly underdoped samples of the high-temperature superconductor Bi-2212 have been conducted at low temperatures where the pseudogap state coexists with superconductivity. The pseudogap phase transition for these materials occurs at relatively high temperatures, $T^* > 300\, K$, a region of the phase diagram which is largely unexplored by STM. Here we present our temperature-dependent STM measurements of the pseudogap state of underdoped Bi-2212 in the vicinity of $T^*$. [Preview Abstract] |
Monday, March 2, 2015 4:18PM - 4:30PM |
D11.00010: Signatures of the Berezinskii$-$Kosterlitz$-$Thouless transition in highly underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ Zhenzhong Shi, Paul Baity, Xiaoyan Shi, Dragana Popovi\'{c} We investigated the nature of the thermally driven transition to a superconducting state on MBE-grown 100 nm thick La$_{2-x}$Sr$_{x}$CuO$_{4}$ films ($x=0.07$ and $0.08$) by studying a) superconducting fluctuations (SCFs), as determined from the magnetoresistance, b) current-voltage ($I-V$) characteristics, and c) fluctuations of conductance with time (noise). Noise was studied on confined width (20 $\mu$m) samples specifically designed for measurements in the eight-probe double-bridge configuration. We observe: a) the contribution of the SCFs to the conductivity increases monotonically with decreasing $T$ and diverges exponentially at $T_{BKT}$, where resistance also goes to zero; b) power-law behavior $V \propto I^{\alpha(T)}$ with $\alpha (T) \geq 3$ for $T\leq T_{BKT}$; and c) an orders-of-magnitude enhancement of the noise near $T_{BKT}$. Possible long-range correlations in the phase fluctuations near $T_{BKT}$ are also studied with higher-order spectrum analysis. Our observations suggest that the transition from superconductor to the normal state exhibits signatures of the Berezinskii$-$Kosterlitz$-$Thouless (BKT) transition. [Preview Abstract] |
Monday, March 2, 2015 4:30PM - 4:42PM |
D11.00011: Double criticality in the magnetic field driven transition of a high-TC superconductor Brigitte Leridon, Johan Vanacken, V.V. Moshchalkov, Baptiste Vignolle, Rajni Porwal, R.C. Budhani The magnetic-field driven transition of a set of high critical temperature $La_{2-x}Sr_{x}CuO_4$ superconducting thin films has been investigated using high pulsed magnetic fields. For the underdoped samples, the existence of two distinct critical regions in the superconductor/insulator transition has been evidenced for the first time. The first quantum critical region is observed at intermediate magnetic fields ($\simeq 19 T$)and temperatures and gives way at lower temperature to a quantum critical point at about twice critical magnetic field and resistance per square. The critical exponents inferred from scaling behaviour are markedly different for the two regions. We attribute this behaviour to the existence of a clean/dirty crossover due to the presence of electronic inhomogeneities.\footnote{Brigitte Leridon, J. Vanacken, V.V. Moshchalkov, Baptiste Vignolle, Rajni Porwal, R.C. Budhani, Cond. Mat. arXiv:1306.4583} [Preview Abstract] |
Monday, March 2, 2015 4:42PM - 4:54PM |
D11.00012: Examining non-Fermi liquid behavior through magnetoresistance in nearly continuously doped La$_{(2-x)}$Sr$_x$CuO$_4$ Zac Stegen, Arkady Shekhter, Greg Boebinger, Fedor Balakirev, Ross McDonald, Jie Wu, Anthony Bollinger, Xi He, Ivan Bozovic We report magnetoresistance in thin films of the cuprate superconductor La$_{(2-x)}$Sr$_x$CuO$_4$ in pulsed magnetic fields up to 65 tesla. The films are synthesized using combinatorial molecular beam epitaxy, which allows for continuous tuning of doping. They are patterned into an array of pixels with steps of $\Delta x \approx 0.0002$, which is 25 times smaller than experiments using conventional sample growth methods. These films allow a detailed analysis of the doping evolution of non-Fermi liquid magnetoresistance in the vicinity of optimal doping. [Preview Abstract] |
Monday, March 2, 2015 4:54PM - 5:06PM |
D11.00013: Magnetic field induced ordering and phase diagram in underdoped LSCO Jesse Hall, Toomas R\~o\~om, Urmas Nagel, Dan H\"uvonen, D. Hawthorne, S. Wakimoto, H. Zhang, Jungseek Hwang, Seiki Komiya, Thomas Timusk The existence of ordered phases in superconducting cuprates has come under intense scrutiny with the revelation of charge-ordering near the superconducting transition in YBCO. Previous results demonstrating the existence of exotic ordered phases, including the existence of stripe order, and the richness of the magnetic-field/doping/temperature phase diagram, suggest that the underdoped region of the phase diagram may contain a wealth of information that has yet to be revealed. We turn our attention to La$_{2-x}$Sr$_x$CuO$_4$ on the boundary of superconductivity by studying the far-infrared optical properties of three single crystals with x=0.05, 0.06, and 0.07; the first is non-superconducting, the others have transition temperatures of 6 K and 12 K respectively. By applying a magnetic field up to 17 T we are able to suppress superconductivity where it exists and compare the field-induced normal state to that induced by temperature or by doping. By studying the optical conductivity of these materials and the changes in the spectral weight with temperature and field, we can gain insight into the field induced ordered states of underdoped cuprate superconductors. [Preview Abstract] |
Monday, March 2, 2015 5:06PM - 5:18PM |
D11.00014: Doping-dependent critical Cooper-pair momentum $p_{c}$ in thin underdoped cuprate films Thomas Lemberger, John Draskovic, Stanley Steers, Thomas McJunkin, Adam Anmed We apply a low-field (\textless 100 G) technique to measure the critical Cooper pair momentum $p_{c}$ in thin, underdoped films of Y$_{\mathrm{0.7}}$Ca$_{\mathrm{0.3}}$Ba$_{\mathrm{2}}$Cu$_{\mathrm{3}}$ O$_{\mathrm{7-\delta }}$ and Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCu$_{\mathrm{2}}$O$_{\mathrm{8+\delta }}$, where doping is effected by adjusting the oxygen stoichiometry through post-deposition annealing. The technique is based on applying a perpendicular magnetic field to the center of a superconducting film and measuring the field at which screening of the field catastrophically fails. Theory together with measurements on thin films of conventional superconductors Nb and MoGe argue for the validity of the technique. In underdoped cuprates, spectroscopy identifies multiple characteristic energy scales, e.g., the pseudogap and the ``nodal'' gap, neither of which is proportional to $T_{c}$. On general grounds, we expect to find that $p_{c} \propto 1 \mathord{\left/ {\vphantom {1 \xi }} \right. \kern-\nulldelimiterspace} \xi $ is proportional to the characteristic superconducting energy scale. We observe that $p_{c} \propto T_{c} $ as $T_{c}$ decreases with underdoping, identifying $k_{B} T_{c} $ as the characteristic energy. While this result is trivial in conventional superconductors whose spectroscopic gaps are proportional to $T_{c}$, it is significant in cuprates. [Preview Abstract] |
Monday, March 2, 2015 5:18PM - 5:30PM |
D11.00015: A mean-field phase diagram with a pair density wave state in relation to cuprate phenomenology Akash Maharaj, Laimei Nie, Eduardo Fradkin, Steven Kivelson The possible role of the pair density wave (PDW) phase in the cuprate phase diagram is discussed. We examine the mean field Landau theory which intertwines PDW order with uniform superconduc- tivity as well as incommensurate spin- and charge-density wave order, and show how many unique experimental features of different cuprate families are qualitatively reproduced naturally from this perspective. In particular, we focus on the existence of subsidiary incommensurate charge order -- both in the presence and absence of a magnetic field -- and show that various observed trends can be understood from this perspective. This, in turn, is consistent with the supposition that the charge ordering phenomena observed in different cuprates have a common underlying origin. [Preview Abstract] |
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