Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session H41: Electronic Nematicity in SuperconductorsInvited
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Sponsoring Units: DCMP DMP Chair: Ivan Bozovic, Brookhaven National Laboratory Room: LACC 502A |
Tuesday, March 6, 2018 2:30PM - 3:06PM |
H41.00001: Observing many body entanglement in strange metals. Invited Speaker: Jan Zaanen In particular the cuprate strange metals represent arguably the most notorious mystery in condensed matter physics. An exciting possibility is that their strangeness is rooted in dense many-body entanglement, of a kind that can only be cracked by a quantum computer. However, it appears that the holographic duality discovered in string theory is a mathematical machinery that may generate universal phenomenological theories describing the physics of such compressible quantum matter. It has proven to be a fertile source of unusual questions to pose to experiment and I will review the state of the art of this development. This includes the relatively mature holographic transport theory revolving around hydrodynamics and Planckian dissipation. Also the latest developments will be highlighted revolving around the instabilities of strange metals, showing that the most salient features of the intertwined order arise naturally from the fanciful black hole haircuts generic in the gravitational dual. |
Tuesday, March 6, 2018 3:06PM - 3:42PM |
H41.00002: Electronic nematicity in cuprates and ruthenates. Invited Speaker: Jie Wu Over the course of extensive experimental studies of La2-xSrxCuO4 films synthesized by molecular beam epitaxy, we discovered that a spontaneous voltage develops across the sample, transverse to the electrical current1. The sign and magnitude of this transverse voltage oscillates with the in-plane direction of the current as a consequence of the anisotropy in electronic transport. This unusual metallic state, in which the rotational symmetry of the electron fluid is spontaneously broken, is of purely electronic origin, the so-called ‘electronic nematicity’. The director of nematicity does not align with the crystal lattice axes. We observe nematicity in a large temperature and doping region; the superconducting state always emerges out of this nematic metal state1. Our newest results showing that electronic nematicity also occurs in superconducting ruthenates will also be presented. |
Tuesday, March 6, 2018 3:42PM - 4:18PM |
H41.00003: Thermodynamic evidence for nematic phase transition at the onset of pseudogap in cuprates Invited Speaker: Yuji Matsuda A long-standing controversial issue in the quest to understand the superconductivity in cuprates is the nature of the enigmatic pseudogap region of the phase diagram. Especially important is whether the pseudogap state is a distinct thermodynamic phase characterized by broken symmetries below the onset temperature Tpg. Here we report torque-magnetometry measurements of anisotropic susceptibility within the ab planes in orthorhombic YBCO with exceptionally high precision. The in-plane anisotropy along [100] direction (Cu-O-Cu direction) displays a significant increase with a distinct kink at Tpg, showing a remarkable scaling behavior with respect to T/Tpg in a wide doping range. The analysis reveals that the rotational symmetry breaking (nematicity) sets in at Tpg in the limit where the effect of orthorhombicity is eliminated. We also performed the same measurements on simple tetragonal Hg1201 with single CuO2 layer. Two-fold susceptibility anisotropy emerges spontaneously at Tpg , providing direct evidence of the broken rotational symmetry. These firmly establish that the nematic phase transition is universal in high-Tc cuprates. Surprisingly, unlike YBCO, the diagonal nematicity along [110] direction develops in Hg1201. Furthermore, the development of the diagonal nematicity is suppressed below the CDW order, implying that the nematicity competes with CDW. |
Tuesday, March 6, 2018 4:18PM - 4:54PM |
H41.00004: Finite Frequency and Nonlinear Elastoresistance Measurements in the Fe-based superconductors Invited Speaker: Johanna Palmstrom Elastoresistance measurements have previously revealed a divergent electronic nematic susceptibility as a universal feature of underdoped Fe-based superconductors upon cooling through the tetragonal-to-orthorhombic structural transition. Elastoresistivity is described by a high rank tensor (fourth-rank +) as it relates changes in resistivity (second-rank) to strain (second-rank) experienced by a material. Recent technical advances have enabled elastoresistance measurements to both go beyond linear response and to measure the frequency dependence (up to 3 kHz) as well as significantly speeding up the data acquisition process. In this talk, in the context of Fe-based superconductors, I will outline the improvements in the elastoresistance technique, including a new AC strain method based on amplitude demodulation. Furthermore, I will show the large role nematic fluctuations play in the isotropic electronic response of these materials—as evidenced by a diverging nonlinear symmetric (A1g) elastoresistance response to antisymmetric (B2g) strain. |
Tuesday, March 6, 2018 4:54PM - 5:30PM |
H41.00005: Enhacement of Superconductivity by Nematic Fluctuations Invited Speaker: Steven Kivelson It is increasingly clear that some form of electron-nematic order arises naturally in a wide variety of highly correlated electron fluids. Sometimes superconductivity with an enhanced Tc appears in the neighborhood of the quantum critical point corresponding to the onset of ground state nematic order. Theoretical reasons to expect a correlation between enhanced superconductivity and strong nematic quantum fluctuations and empirical tests of a causal relation between the two will be discussed. |
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