Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session C23: Discoveries on the Spectrum of Fluctuations Responsible for Superconductivity and Normal State Anomalies in CupratesInvited
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Sponsoring Units: DCMP Chair: Dunghai Lee, University of California, Berkeley Room: New Orleans Theater B |
Monday, March 13, 2017 2:30PM - 3:06PM |
C23.00001: Quantitative Determination of the Pairing Interactions for High Temperature Superconductivity in Cuprates Invited Speaker: Xingjiang Zhou A profound problem in modern condensed matter physics is to discover and understand the nature of the fluctuations and their coupling to fermions in cuprates which lead to high temperature superconductivity and the associated strange-metal normal state. In this talk, we will report the quantitative determination of the normal and pairing self-energies, made possible by laser-based angle-resolved photoemission measurements with unprecedented accuracy and stability. Through a precise inversion procedure, both the effective interactions in the attractive d-wave symmetry and the repulsive part in the full symmetry are determined. Besides finding the pairing self-energy and the attractive interactions for the first time, these results expose a central paradox of the high Tc problem: how the same frequency independent fluctuations can dominantly scatter at angles $+$-pi/2 in the attractive channel as well as lead to angle-independent repulsive scattering. The experimental results will be compared with the available theoretical calculations based on antiferromagnetic fluctuations, Hubbard model and the quantum-critical fluctuations of loop-current order. *This work is done in collaboration with Jin Mo Bok, Jong Ju Bae, Han-Yong Choi, Chandra M. Varma, Wentao Zhang, Junfeng He, Yuxiao Zhang and Li Yu [1]. J. M. Bok et al., Science Advances 2, e1501329 (2016). [Preview Abstract] |
Monday, March 13, 2017 3:06PM - 3:42PM |
C23.00002: Theory of Strange Metals and high Temperature superconductors Invited Speaker: Chandra Varma The discovery of high temperature superconductivity almost thirty years ago opened a rich vein of unsuspected and beautiful quantum phenomena. The vast experimental effort that followed has led to many different illustrations of new principles at work. This has been matched by intense theoretical effort, sometimes with deep ideas. I will describe a direction in which the central organizing principle is quantum-critical fluctuations, in some metals of antiferromagnetic order, and in cuprates of a new class of order. The statistical mechanical model for both is the dissipative quantum XY model. The quantum-criticality of this model is driven by topological excitations and not renormalized spin-waves as in the usual theory. The correlation functions are products of functions of frequency with $\omega/T$ scaling and functions of momenta with spatial correlation length proportional to the logarithm of the temporal correlation length. A thorough examination of a variety of experimental results in the normal and superconducting state suggests that this form of critical fluctuations with the associated coupling to fermions is uniquely responsible for the phenomena. [Preview Abstract] |
Monday, March 13, 2017 3:42PM - 4:18PM |
C23.00003: Strongly correlated superconductivity and quantum criticality Invited Speaker: A.-M.S. Tremblay Doped Mott insulators and doped charge-transfer insulators describe classes of materials that can exhibit unconventional superconducting ground states. Examples include the cuprates and the layered organic superconductors of the BEDT family. I present results obtained from plaquette cellular dynamical mean-field theory. Continuous-time quantum Monte Carlo evaluation of the hybridization expansion allows one to study the models in the large interaction limit where quasiparticles can disappear. The normal state which is unstable to the superconducting state exhibits a first-order transition between a pseudogap and a correlated metal phase. That transition is the finite-doping extension of the metal-insulator transition obtained at half-filling. This transition serves as an organizing principle [1] for the normal and superconducting states of both cuprates [2] and doped organic superconductors [3]. In the less strongly correlated limit, these methods also describe the more conventional case where the superconducting dome surrounds an antiferromagnetic quantum critical point [4]. \\ --- [1] L. Fratino, P. S\'emon, G. Sordi and A.-M.S. Tremblay An organizing principle for two-dimensional strongly correlated superconductivity Sci. Rep., 6, 22715 (2016). --- [2] L. Fratino, P. S\'emon, G. Sordi, and A.-M. S. Tremblay Pseudogap and superconductivity in two-dimensional doped charge-transfer insulators Phys. Rev. B 93, 245147 (2016) --- [3] Charles-David H\'ebert, Patrick S\'emon, and A.-M. S. Tremblay Superconducting dome in doped quasi-2d organic Mott insulators: A paradigm for strongly-correlated superconductivity Phys. Rev. B 92, 195112 (2015). --- [4] Wei Wu, A.-M.S. Tremblay d-wave superconductivity in the frustrated two-dimensional periodic Anderson model Phys. Rev. X 5, 011019 (2015). [Preview Abstract] |
Monday, March 13, 2017 4:18PM - 4:54PM |
C23.00004: Evidence of a global inversion-symmetry-broken phase in the pseudogap region of YBa$_2$Cu$_3$O$_y$ Invited Speaker: David Hsieh The temperature versus doping phase diagram of the cuprate high-temperature superconductors features an enigmatic pseudogap region that is characterized by a partial suppression of low energy electronic excitations. Identifying the complete set of symmetries underlying the pseudogap region is imperative to understanding its microscopic nature and relationship to superconductivity. In this talk I will describe the results of highly symmetry sensitive optical second harmonic generation experiments on YBa$_2$Cu$_3$O$_y$ across a wide temperature and doping range using a recently developed nonlinear optical rotational anisotropy technique. I will show evidence of a global inversion-symmetry-broken order that onsets at the pseudogap temperature and persists inside the superconducting dome in the overdoped regime, but shows no coupling to either charge density wave or superconducting order parameters. I will then discuss how these results relate to previous polarized neutron diffraction, Nernst effect and THz polarimetry data on YBa$_2$Cu$_3$O$_y$. Finally, I will show evidence of a remarkably similar phenomenon occurring in doped Sr$_2$IrO$_4$, a strongly spin-orbit coupled analog of La$_2$CuO$_4$, hinting at a robust connection between this hidden order and pseudogap physics that extends beyond the cuprates. [Preview Abstract] |
Monday, March 13, 2017 4:54PM - 5:30PM |
C23.00005: A non-equilibrium approach to the optical spectroscopy of high-temperature superconductors Invited Speaker: Fulvio Parmigiani Non-equilibrium spectroscopies of high temperature superconductors have evolved in the last two decades from avant-garde studies to a crucial tool for understanding the physics of high temperature superconductors. In particular, the possibility of obtaining both spectral and temporal information simultaneously leads to insights that are complementary (and in some instances beyond to) those attainable by conventional equilibrium experiments. This presentation is focused on the still unresolved problem of the origin of the pseudo-gap in cuprates, one of the major open issues about copper-oxides based superconductors. Indeed, the ubiquitous phenomenology of the pseudo-gap, occupying a wide region of the phase diagram, is not understood yet. Its comprehension could provide clue information about the microscopic mechanisms of these materials and their phase diagram. We investigate the pseudo-gap with non-equilibrium approach, that allows to disentangle the intertwined degrees of freedom (carrier, lattice. long range order) by their timescale. [Preview Abstract] |
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