Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R04: "Whither Pairing Correlations or Quantum Criticality driven Pseudogap in the Cuprate Superconductors?"Invited
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Sponsoring Units: DCMP DCP Chair: Laura Greene, Florida State Univ Room: LACC 151 |
Thursday, March 8, 2018 8:00AM - 8:36AM |
R04.00001: The quantum critical point of cuprate superconductors Invited Speaker: Louis Taillefer I will present recent experimental studies performed using high magnetic fields to suppress superconductivity and access the non-superconducting ground state of cuprates in the T = 0 limit. These reveal the presence of a quantum critical point in the phase diagram of cuprates [1,2,3], where the enigmatic pseudogap phase ends, around which the superconducting phase forms a dome, and at which the resistivity exhibits an anomalous linear dependence on temperature [4,5]. |
Thursday, March 8, 2018 8:36AM - 9:12AM |
R04.00002: Topological skyrmion pseudogap in the cuprate superconductors Invited Speaker: Catherine Pepin We consider a theory for the formation of the pseudo-gap in the underdoped region of cuprate superconductors, in which there is a large regime of fluctuations between the d-wave SC order and d-wave charge density modulations. These fluctuations involve the phase as well as the amplitude of each order parameter and can be described within an emerging SU(2) symmetry. The theory captures large part of the phenomenology of the cuprates. We will discuss experimental prediction of this theory, including the presence of collective modes and the generation of unusual topological defects in the pseudo-spin space. We will outline the differences between the SU(2) fluctuation approach to strong coupling scenarios involving the fractionalization of the electron. |
Thursday, March 8, 2018 9:12AM - 9:48AM |
R04.00003: Strong Magnetic Fields at the Crossroads of Superconductivity, Quantum Criticality and Fermi Surface Reconstruction in the Cuprates Invited Speaker: Neil Harrison A central question in high-$T_{\rm c}$ superconductivity concerns whether the pseudogap hosts a normal metallic ground state in the absence of superconductivity. High field measurements have thus far been reported the suppression of superconductivity to yield either a metallic pseudogap ground state, characterized by properties such as magnetic quantum oscillations, magnetotransport and signatures in the thermal conductivity, or a vortex liquid ground state characterized by properties such as diamagnetism. In this talk, I will present electrical transport measurements in both pulsed magnetic fields extending to 90~T and static magnetic fields of up to 45~T, over several decades in temperature and current density and over a wide range of YBa$_2$Cu$_3$O$_{6+x}$ hole dopings, performed in collaboration with Yu-Te Hsu, Mate Hartstein, Alexander J. Davies, Mun K. Chan, Juan Porras, Toshinao Loew, Sofia V. Taylor, Hsu Liu, Mathieu Le Tacon, Huakun Zuo, Jinhua Wang, Zengwei Zhu, Gilbert G. Lonzarich, Bernhard Keimer, and Suchitra E. Sebastian. We find evidence for a previously concealed robust superconducting state up to very high magnetic fields. Our high field measurements reveal an unusual pseudogap state in which seemingly metallic properties likely arise from the nodal region of minimal or suppressed superconducting gap, while the antinodal regions of maximal superconducting gap are dominated by large amplitude pairing correlations. |
Thursday, March 8, 2018 9:48AM - 10:24AM |
R04.00004: New insight into the cuprate phase diagram from measurements of HgBa2CuO4+δ Invited Speaker: Martin Greven The discovery of high-temperature superconductivity in the cuprates more than three decades ago triggered a tremendous amount of scientific activity, yet it has remained a challenge to understand the unusual ‘normal’ state from which the superconductivity evolves upon cooling. I will review our collaborative neutron scattering, X-ray scattering, torque magnetometry and charge transport results for HgBa2CuO4+δ, arguably one of the most ideal cuprate compounds for experimental study due to its high structural symmetry and high optimal superconducting transition temperature of nearly 100 K. From the comparison with data for other cuprates we are able to separate underlying universal properties from compound-specific behavior. Our results point to the existence of two electronic subsystems, and to an essential role played by nanoscale inhomogeneity inherent to these lamellar oxides. We conclude that the combination of inhomogeneity and two-component physics drives percolative behavior on multiple energy scales, giving rise to universal characteristics of the normal state and of the emergence of superconductivity. |
Thursday, March 8, 2018 10:24AM - 11:00AM |
R04.00005: Closing the gaps in our understanding of the pseudogap Invited Speaker: Antoine Georges In this talk, I will review recent theoretical progress in understanding the pseudogap phenomenon in the two-dimensional Hubbard model, in relation to hole-doped cuprate superconductors. I will show that two independent computational methods (cluster extensions of dynamical mean-field theory, and lattice diagrammatic Monte Carlo) yield quantitatively consistent results. These two methods indicate that short-range antiferromagnetic correlations are responsible for the opening of the pseudogap in the strong-coupling regime. The Fermi surface is strongly modified by interactions, and a pseudogap only opens when this surface is hole-like. For small to moderate ratios of t’/t, the collapse of the pseudogap is found to coincide with the Lifshitz transition of the Fermi surface from hole-like to electron-like, in agreement with experimental observations. These findings can be rationalized within an SU(2) gauge theory of a metal with short-range fluctuating antiferromagnetic order, in which topological order is responsible for the reconstruction of the Fermi surface into pockets. |
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