Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session A1: Charge Order and the Pseudogap in the Underdoped CupratesInvited
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Sponsoring Units: DCMP Chair: Tom Devereaux, Stanford University Room: Ballroom I |
Monday, March 14, 2016 8:00AM - 8:36AM |
A1.00001: Towards a complete Fermi surface in underdoped high $T_{\rm c}$ superconductors Invited Speaker: Neil Harrison The discovery of magnetic quantum oscillations in underdoped high $T_{\rm c}$ superconductors raised many questions, and initiated a quest to understand the origin of the Fermi surface the like of which had not been seen since the very first discovery of quantum oscillations in elemental bismuth. While studies of the Fermi surface of materials are today mostly assisted by computer codes for calculating the electronic band structure, this was not the case in the underdoped high Tc materials. The Fermi surface was shown to reconstructed into small pockets, yet there was no hint of a viable order parameter. Crucial clues to understanding the origin of the Fermi surface were provided by the small value of the observed Fermi surface cross-section, the negative Hall coefficient and the small electronic heat capacity at high magnetic fields. We also know that the magnetic fields were likely to be too weak to destroy the pseudogap and that vortex pinning effects could be seen to persist to high magnetic fields at low temperatures. I will show that the Fermi surface that appears to fit best with the experimental observations is a small electron pocket formed by connecting the nodal `Fermi arcs' seen in photoemission experiments, corresponding to a density-wave state with two different orthogonal ordering vectors. The existence of such order has subsequently been detected by x-ray scattering experiments, thereby strengthening the case for charge ordering being responsible for reconstructing the Fermi surface. I will discuss new efforts to understand the relationship between the charge ordering and the pseudogap state, discussing the fate of the quasiparticles in the antinodal region and the dimensionality of the Fermi surface. The author acknowledges contributions from Suchitra Sebastian, Brad Ramshaw, Mun Chan, Yu-Te Hsu, Mate Hartstein, Gil Lonzarich, Beng Tan, Arkady Shekhter, Fedor Balakirev, Ross McDonald, Jon Betts, Moaz Altarawneh, Zengwei Zhu, Chuck Mielke, James Day, Doug Bonn, Ruixing Liang, Walter Hardy. [Preview Abstract] |
Monday, March 14, 2016 8:36AM - 9:12AM |
A1.00002: Three-dimensional charge density wave order in YBCO at high magnetic field Invited Speaker: Wei-Sheng Lee Charge density wave (CDW) correlations have been shown to universally exist in cuprate superconductors. However, their nature at high magnetic fields, $e.g. $inferred from nuclear magnetic resonance, Hall coefficient, and sound velocity measurements, is distinct from that measured by x-ray scattering at zero and low fields. In this talk, I will discuss our recent experiment which combines a pulsed magnet with an x-ray free electron laser to characterize the CDW in YBa$_{2}$Cu$_{3}$O$_{6.67}$ via x-ray scattering in fields up to 28 Tesla. While the zero-field CDW order, which develops below \textasciitilde 150 K, is essentially two dimensional, a three-dimensionally ordered CDW emerges at magnetic fields beyond 15 Tesla and at temperatures below the zero-field superconducting transition temperature. While the two CDW arrange differently along the c-axis, they share the same incommensurate periodicity in the CuO$_{2\, }$plane. Our observations imply that the two forms of CDW and high-temperature superconductivity are intimately linked. [Preview Abstract] |
Monday, March 14, 2016 9:12AM - 9:48AM |
A1.00003: Fractionalized Fermi liquids and the pseudogap Invited Speaker: Subir Sachdev Fractionalized Fermi liquids (FL*) are metals with Fermi surfaces of electron-like quasiparticles; however the volume enclosed by the Fermi surface is not equal to the Luttinger value determined by the density of all electrons. There are general non-perturbative arguments that any such state with a non-Luttinger volume must also have emergent gauge excitations which have vanishing energy on manifolds of non-trivial topology. In doped antiferromagnets with hole density $p$, the Luttinger volume of a closed Fermi surface of holes is $1+p$ in the state without antiferromagnetic order. Simple FL* models of doped antiferromagnets will be described with ground states which preserve all symmetries, and have hole pockets of total volume $p$. Such models provide natural explanations for a number of recent observations on the pseudogap phase of the hole-doped cuprate superconductors. Confinement transitions of such FL* phases to conventional phases will also be described. [Preview Abstract] |
Monday, March 14, 2016 9:48AM - 10:24AM |
A1.00004: Charge order in cuprates: from hole to electron doping. Invited Speaker: Andrea Damascelli Charge ordering has resurged as a prominent phenomenon in the physics of high-Tc cuprates. In this talk I will review our recent results from Bi2201 [1,2] and YBCO hole-doped cuprates [3,4], as well as electron doped NCCO [5]. With the early discovery of stripe-like order in La-based cuprates, this establishes charge ordering instabilities to be omnipresent in all cuprate families. I will discuss the connection between charge ordering and pseudogap phenomenology [2,5], similarities and asymmetries between hole and electron doping [2,5], and the native local symmetry of charge modulations [3,4].\\ \\1) J.A. Rosen et al., Nature Communications 4, 1977 (2013). 2) R. Comin et al., Science 343, 390 (2014). 3) R. Comin et al., Science 347, 1335 (2015). 4) R. Comin et al., Nature Materials, 14, 796-800 (2015). 5) E.H. da Silva Neto et al., Science 347, 282 (2015). [Preview Abstract] |
Monday, March 14, 2016 10:24AM - 11:00AM |
A1.00005: Short ranged orders in numerical data and STM data, their mechanism and roles. Invited Speaker: Eun-Ah Kim Withe revent experimental break through establishing the short-ranged spin and charge order as universal phenomena in under-doped cuprates, both the origin and the role of these local ordering tendencies take the center stage of cuprates research. In this talk, I will present anays is of short-ranged charge order observed in both our numerical data on multi-band spin-Fermi on model and scanning tunneling spectroscopy data. I will discuss the implications of the results in the context of the origin and the role of charge order. [Preview Abstract] |
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