Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session Y53: Invited Session: Cuprate Pseudogap, Charge Density Wave and Pair Density Wave |
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Sponsoring Units: DCMP Chair: Steven Kivelson, Stanford University Room: Grand Ballroom C3 |
Friday, March 6, 2015 8:00AM - 8:36AM |
Y53.00001: The microscopic structure of charge order in cuprates Invited Speaker: Riccardo Comin The spontaneous self-arrangement of electrons into periodically modulated patterns, a phenomenon commonly termed as charge order or charge-density-wave (CDW), has recently resurfaced as a prominent, universal ingredient for the physics of high-temperature superconductors. In such context, resonant x-ray scattering (RXS) has rapidly become the technique of choice for the study of charge order in momentum space, owing to its ability to directly identify a breaking of translational symmetry in the electronic density. In this talk, I will present our recent RXS studies of charge order in Bi2201, which reconciled years of apparently disconnected findings in different cuprate families by showing how charge order is a universal phenomenon in hole-doped cuprates [R. Comin, \textit{et al}., Charge Order Driven by Fermi-Arc Instability in Bi2Sr2$-$ xLaxCuO6$+$d, Science 343, 390 (2014)]. Contextually, I will discuss very recent findings of charge order in NCCO, which project such phenomenology to the electron-doped materials [E. da Silva Neto*, R. Comin*, \textit{et al.,} Charge ordering in the electron-doped superconductor Nd2-xCexCuO4, accepted (2014) -- preprint at: http://arxiv.org/abs/1410.2253]. Furthermore, in YBCO, we have succeeded to fully reconstruct the CDW order parameter in the two-dimensional momentum space and demonstrate how resonant x-ray methods can be used to peer into the microscopic structure and symmetry of the charge order. Using this new method, we have been able to demonstrate the presence of charge stripes at the nanoscale [R. Comin, \textit{et al.,} Broken translational and rotational symmetry via charge stripe order in underdoped YBa2Cu3O6$+$y, under review (2014)], as well as evaluate the local symmetry in the charge distribution around the Cu atoms, which was found to be predominantly of a d-wave bond-order type [R. Comin, \textit{et al.,} The symmetry of charge order in cuprates, under review (2014) -- preprint at: http://arxiv.org/abs/1402.5415]. [Preview Abstract] |
Friday, March 6, 2015 8:36AM - 9:12AM |
Y53.00002: Searching for spectroscopic signatures of density wave correlations in cuprates Invited Speaker: Rui-Hua He Recent developments in the research on high-temperature cuprate superconductors highlight the relevance of some density wave correlations to the superconductivity and its normal state in this generic class of materials. Depending on specific cuprate systems, these density wave correlations can have diverse manifestations in different (charge, spin, pairing) sectors and likely break (time reversal, space inversion, point group, gauge) symmetries in addition to the lattice translation. A unified understanding of their microscopic nature hinges on further characterizations using direct (imaging scattering) probes for these correlations themselves, as well as indirect probes for their interplay with other degrees of freedom in the system. ARPES can provide information about a density wave order through probing modifications in the electron structure it induces, while other spectroscopy techniques can shed unique lights on the broken symmetry aspect of the order. In this talk, I will review the density-wave signatures that have been or yet to be found in ARPES mainly in terms of the spectral weight, energy gap, and renormalized band dispersions. These experimental observations/proposals, coupled with simple theoretical modeling, promise new insights into the (wavevector, order parameter, form factor) characters of associated density wave correlations. Time permitting, I will introduce a novel x-ray spectroscopy technique that can detect broken time-reversal versus space-inversion symmetry of an electronic order in a way complementary to the polar Kerr effect. [Preview Abstract] |
Friday, March 6, 2015 9:12AM - 9:48AM |
Y53.00003: Amperean (2k\textunderscore F) pairing and the pseudo-gap phase in HiTc Cuprates Invited Speaker: Patrick Lee We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional BCS theory which pairs electrons on opposite sides of the Fermi surface. The pair carries a net momentum 2k\textunderscore F, forming a pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order appears as a subsidiary order parameter even when pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. Finally, we propose an experiment that can directly test the idea of Amperean pairing. [Preview Abstract] |
Friday, March 6, 2015 9:48AM - 10:24AM |
Y53.00004: Charge ordered normal ground state and its interplay with superconductivity in the underdoped cuprates Invited Speaker: Suchitra Sebastian Over the last few years, evidence has gradually built for a charge ordered normal ground state in the underdoped region of the cuprate high temperature superconductors. I will address the electronic structure of the normal ground state of the underdoped cuprates as accessed by quantum oscillations, and relate it to complementary measurements by other experimental techniques. The interplay of the charge ordered ground state with the antinodal gapped pseudogap state, and overarching magnetic and superconducting correlations will be further explored. \\[4pt] This work was performed in collaboration with N. Harrison, G. G. Lonzarich, B. J. Ramshaw, B. S. Tan, P. A. Goddard, F. F. Balakirev, C. H. Mielke, R. Liang, D. A. Bonn, and W. N. Hardy [Preview Abstract] |
Friday, March 6, 2015 10:24AM - 11:00AM |
Y53.00005: Local Dimensionality of the Charge Density Wave in the Superconducting Cuprate Bi2201 Invited Speaker: Jennifer Hoffman Charge density wave (CDW) states were recently recognized as universal throughout the surface and bulk of a number of cuprates [1], prompting widespread effort to understand both their detailed phenomenology and their relationship to the mechanism of superconductivity. However, the dimensionality of the charge modulations remains unclear, including whether the modulation wavevector is unidirectional or bidirectional in-plane, and also the extent of inter-plane coherence of the charge modulations. In bismuth-based cuprates, severe material disorder precludes answering these questions through bulk scattering techniques. We use a local technique, scanning tunneling microscopy, to image the static charge modulations in (Pb,Bi)$_2$(Sr,La)$_2$CuO$_{6+x}$ (Bi2201). We find that the charge modulations are more consistent with an underlying tendency to unidirectional than bidirectional CDW. Using recently developed cluster analysis techniques, we further show that these locally unidirectional CDWs extend coherently into the bulk of the material throughout the doping range. Finally, we comment on their relationship to a Fermi surface transition and quantum critical point observed in Bi2201 [3]. \\[4pt] [1] R. Comin, A. Frano, M. M. Yee, Y. Yoshida, H. Eisaki, E. Schierle, E. Weschke, R. Sutarto, F. He, A. Soumyanarayanan, Y. He, M. LeTacon, I. Elfimov, J.E. Hoffman, B. Keimer, G.A. Sawatzky, A. Damascelli ``Charge ordering driven by Fermi-arc instability in underdoped cuprates.'' \textit{Science} \textbf{343}, 390 (2014)\\[0pt] [2] B. Phillabaum, E.W. Carlson, K.A. Dahmen, ``Spatial complexity due to bulk electronic nematicity in a superconducting underdoped cuprate.'' \textit{Nature Communications} \textbf{3}, 915 (2012).\\[0pt] [3] Yang He, Yi Yin, M. Zech, Anjan Soumyanarayanan, Michael M. Yee, Tess L. Williams, M. C. Boyer, Kamalesh Chatterjee, W. D. Wise, Ilija Zeljkovic, Takeshi Kondo, T. Takeuchi, H. Ikuta, Peter Mistark, Robert S. Markiewicz, Arun Bansil, E. W. Hudson, Jennifer E. Hoffman, ``Fermi Surface and Pseudogap Evolution in a High $T_c$ Superconductor.'' \textit{Science} \textbf{344}, 608 (2014). [Preview Abstract] |
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