Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P08: Superconductivity: Copper Oxide - Fermiology and Phase Diagram |
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Sponsoring Units: DCMP Chair: Makariy Tanatar, Ames Laboratory Room: BCEC 150 |
Wednesday, March 6, 2019 2:30PM - 2:42PM |
P08.00001: Fermi-surface morphology and signatures of quantum critical points in the high-Tc cuprate HgBa2CuO4+δ revealed by high-magnetic fields Mun Chan, Neil Harrison, Ross McDonald, Eric Bauer A paradigm of unconventional superconductivity invoked for the cuprates is that the unusually high superconducting temperatures is caused by strong electronic interactions near a zero temperature phase transition termed a quantum critical point (QCP). We report measurements of the low temperature electronic structure of the single-layer cuprate featuring the highest superconducting temperatures, HgBa2CuO4+δ (Hg1201). Quantum oscillations indicate that the Fermi surface is comprised of only a single quasi-two dimensional pocket that likely results from Fermi-surface reconstruction by a charge density wave order. High magnetic field measurements up to 90 T allow us to determine the boundaries of this order and identify two putative quantum critical points. Measurements of the doping dependent effective mass and upper critical fields provide additional support for strong-correlations around these QCPs. |
Wednesday, March 6, 2019 2:42PM - 2:54PM |
P08.00002: Probing the Fermi surface of Nd-LSCO with angle-dependent magnetoresistance measurements Yawen Fang, Anaelle Legros, Gael Grissonnanche, Francis Laliberte, Paul Goddard, Louis Taillefer, Brad Ramshaw Characterizing the Fermi surface of high-temperature sperconductors in the pseudogap phase is one of the major challenges in understanding the origin of this mysterious partial gap in the electronic density of states. The Fermi surface between p=0.08 and p=0.15, the same doping range where charge order is observed, has been determined via quantum oscillations to be a small electron pocket. Above the critical doping p*, in the Fermi-liquid phase, a single large hole surface has been reported. However, in the pseudogap phase, the topology of the Fermi surface at low temperature in the absence of superconductivity or charge-density-wave order is still unknown. To study the topology of this Fermi surface, we performed an angle-dependent magetoresistance (ADMR) study of Nd-LSCO. We measured the ADMR of single crystal La1.6-xNd0.4SrxCuO4 (Nd-LSCO) with x=p=0.2,0.21,0.22,0.23,0.25, up to 45 tesla and down to 6 kelvin. At p=0.25, above p*, we find a large Fermi surface whose geometry is consistent with that observed by ARPES, but with a strongly anisotropic quasiparticle lifetime. Below p*, in the pseudogap state, we observe a dramatic change in the ADMR, and preliminary analysis suggests that strong anti-nodal scattering is responsible. |
Wednesday, March 6, 2019 2:54PM - 3:06PM |
P08.00003: Superconducting Higgs mode in cuprate thin films Hao Chu, Min-Jae Kim, Kota Katsumi, Sergey Kovalev, Robert Dawson, Lukas Schwarz, Naotaka Yoshikawa, Gideok Kim, Semyon Germanskiy, Jan-Christoph Deinert, Nilesh Awari, Bertram W Green, Min Chen, Mohammed Bawatna, Georg Cristiani, Gennady Logvenov, Yann Gallais, Alexander Boris, Bernhard Keimer, Andreas P Schnyder, Dirk Manske, Michael Gensch, Zhe Wang, Ryo Shimano, Stefan Kaiser Cuprate high-Tc superconductor hosts multiple competing orders such as the pseudogap, incommensurate magnetism, charge order, etc. These diverse phases were discovered via spectroscopy tools that probe the charge-/spin-excitations of an ordered state. Yet, despite the immense knowledge about cuprates learnt from these experiments, a coherent understanding of the microscopic mechanism behind high-Tc superconductivity is still lacking. A potential answer to this question may come from investigating the collective excitation of the superconducting order parameter itself, which is charge- and spin-neutral and difficult to access by conventional techniques. We accomplish this goal by using an undulator-based high-field THz pulse, which nonlinearly couples to the superconducting condensate and leads to characteristic third harmonic generation. Using this technique, we unveil the collective amplitude oscillation of the superconducting order parameter, the superconducting Higgs mode, in three archetypal families of cuprates for the first time. In addition, we show evidence for a hitherto unreported collective mode universally exhibited by optimally doped samples. A finite Higgs-like response above Tc is also observed in our experiment, suggesting a finite pairing amplitude above Tc. |
Wednesday, March 6, 2019 3:06PM - 3:18PM |
P08.00004: Breaking the universal Tc-P relation to higher Tc of cuprate HTS Ching-Wu Chu, Liangzi Deng, Yongping Zheng, Zheng Wu, Shuyuan Huyan, Hung-Cheng Wu, Kyeongjae Cho By investigating the bulk superconducting state via dc magnetization measurements, we have discovered the resurgence of the superconductive transition temperature Tcs of the monolayer Bi2Sr2CuO6+δ and bilayer Bi2Sr2CaCu2O8+δ to beyond the maximum Tc-maxs predicted by the universal Tc-P relation at higher pressures. We have attributed the resurgence to a possible pressure-induced electronic transition in the compounds, associated with a charge transfer between the Cu 3dx2-y2 and the O 2p bands, leading to an increase of the density of states at the Fermi level, in agreement with our density functional theory calculations. Similar Tc-P behavior has also been reported in the trilayer Br2Sr2Ca2Cu3O10+δ. The observations suggest that higher Tcs in the layered cuprate high temperature superconductors than those previously reported can be achieved by breaking away from the universal Tc-P by the application of higher pressures. |
Wednesday, March 6, 2019 3:18PM - 3:30PM |
P08.00005: Thermoelectric evidence of anomalous quantum criticality in the electron-doped cuprates Pampa Mandal Sarkar, Tarapada Sarkar, Richard L. Greene In electron-doped cuprates, the low upper critical field allows one to study the putative quantum critical phenomena at low temperature and to understand its connection to the long standing problem of the origin of high-Tc superconductivity. We have measured the low temperature normal state thermopower (S) of the electron-doped cuprate superconductor La2-xCexCuO4 (LCCO) from x=0.11 to 0.19. We observe quantum critical S/T versus ln(1/T) behavior over an unexpectedly wide doping range x = 0.15 - 0.17 above the putative QCP (x=0.14) with a slope that scales monotonically with the superconducting transition temperature. We find similar behaviour in another n-type cuprate, PCCO, strongly indicating that this is a universal behaviour in electron-doped cuprates. The presence of quantum criticality over a wide doping range provides a new window on the criticality. The thermopower behavior also suggests that the critical fluctuations are linked with Tc. For x = 0.11 and 0.13, S/T has a completely different behavior, an indication of a Fermi surface reconstruction. Above the superconductivity dome, at x=0.19, a conventional Fermi-liquid S∝T behavior is found for T≤40 K. |
Wednesday, March 6, 2019 3:30PM - 3:42PM |
P08.00006: Josephson interferometry measurements of the superconducting pairing symmetry in the overdoped cuprate La1.75Sr0.25CuO4 --- search for disorder-induced deviations from d-wave symmetry David Hamilton, Masaki Fujita, Dale J Van Harlingen Extensive measurements have shown that cuprate superconductors exhibit a robust dx2-y2 global superconductor pairing symmetry. It has been proposed that in a disordered d-wave superconductor near criticality, the superconductivity will nucleate in spatially-separated puddles with orthogonal phase alignment of the d-wave order parameter. When these puddles are dilute, such as in highly overdoped samples, Josephson coupling between puddles can favor global s-wave superconductivity. To explore this regime, we perfromed Josephson interferometry measurements of LSCO-Au-Nb Josephson junctions formed on edges and corners of an overdoped single crystal of La1.75Sr0.25CuO4 with a Tc of ~18K. In preliminary measurements of Ic vs. magnetic field, we observe deviations from Fraunhofer patterns expected for uniform edge junctions and from the characteristic corner junction pattern expected for dx2-y2 symmetry. We see rapid modulations in the critical current indicating the presence of discrete order parameter domains with opposite sign. At temperatures near where the junction supercurrent vanishes, we observe diffraction patterns with a maximum centered on zero field in the corner junctions, as we would expect to see in an s-wave superconductor. |
Wednesday, March 6, 2019 3:42PM - 3:54PM |
P08.00007: The New NMR Shift and Relaxation Scenario of the Cuprates Juergen Haase Based on experiments and a comprehensive literature analysis of cuprate NMR shift and relaxation data we present the new scenario for the cuprates. It has almost ubiquitous fermionic excitations that govern the nuclear relaxation above Tc and begin to disappear below Tc, i.e., for all materials from slightly underdoped to heavily overdoped. For the highest doping levels, this nuclear relaxation is related to the sample’s spin shift via the Korringa relation for a simple Fermi liquid to which the nuclei couple isotropically. Therefore, it is argued that the spin shifts of the cuprates are typically suppressed, already in the overdoped region, and that there is no enhanced nuclear relaxation compared to that of a Fermi liquid. This means, no spin fluctuations have to be invoked to explain the difference between shift and relaxation. This suppression of the shift above Tc must be related to the pseudogap, which enters nuclear relaxation only through a temperature independent change in the anisotropy of the coupling of the nuclei to the electronic bath. It is argued that two antiferromagnetically coupled spin components that have different orbital origin can explain all the data, even the NMR orbital shift conundrum. |
Wednesday, March 6, 2019 3:54PM - 4:06PM |
P08.00008: Apical charge flux-modulated in-plane transport properties of cuprate superconductors Xin Li, Sooran Kim, Xi Chen, William Fitzhugh For copper-based superconductors, the maximum superconducting transition temperature, Tc,max, of different families measured from experiments can vary by an order of magnitude from 38 K in La2CuO4 to 135 K in HgBa2Ca2Cu3O8 at optimal hole doping concentration. We demonstrate herein, using ab initio computations, a new trend suggesting that the cuprates with stronger out-of-CuO2-plane chemical bonding between the apical anion (O, Cl) and apical cation (e.g. La, Hg, Bi, Tl) are generally correlated with higher Tc,max in experiments. We then show the underlying fundamental phenomena of coupled apical charge flux and lattice dynamics when the apical oxygen oscillates vertically. This triggers the charge flux among the apical cation, apical anion and the in-plane CuO4 unit. The effect not only dynamically modulates the site energy of the hole at a given Cu site to control the in-plane charge transfer energy, but also can modulate the in-plane hole hopping integral in a dynamic way by the cooperative apical charge fluxes. |
Wednesday, March 6, 2019 4:06PM - 4:18PM |
P08.00009: Non-equilibrium study of the phase diagram of cuprates Fabio Boschini, Elia Razzoli, Marta Zonno, Ryan P Day, Matteo Michiardi, Eduardo H Da Silva Neto, Genda Gu, Sergey Zhdanovich, Arthur K Mills, Giorgio Levy, David J Jones, Claudio Giannetti, Andrea Damascelli The phase diagram of cuprates hosts numerous intertwined phases, such as high-temperature superconductivity, charge order and the pseudogap phenomenon. This makes the precise description of each separate phase challenging. In particular, thermal excitations govern the appearance of different phases and thermodynamic phase transitions. We recently demonstrated the capability to study the superconductor-to-normal state transition in Bi2Sr2CaCu2O8+δ cuprate superconductor in an ultrafast fashion. In particular, we demonstrated that time-resolved photoemission spectroscopy can disentangle the dynamics of phase fluctuations and charge excitation, establishing the dominant role of phase coherence in the emergence of high-temperature superconductivity [1]. In the same line of thought, we applied this non-equilibrium approach to (i) reveal the transient competition between charge-order and superconducting phases and (ii) explain the enhanced electron-boson band renormalization (kink) in terms of the opening of the superconducting gap and pseudogap. |
Wednesday, March 6, 2019 4:18PM - 4:30PM |
P08.00010: Fluctuating superconductivity and absence of charge order in heavily overdoped cuprate Bi-2212 Yu He, Sudi Chen, Makoto Hashimoto, Alex Frano, Ming Yi, Yu Song, Shan Wu, Dongjoon Song, Hiroshi Eisaki, Robert J Birgeneau, Zhixun Shen We identify significant superconducting fluctiations on a single coherent, hole-like Fermi surface in heavily overdoped cuprate superconductor Bi-2212. No evidence of pseudogap or valence electron charge order are found in the meantime. Both ampitude and phase fluctuations are quantitatively estimated via measurements of resisitivity anisotropy, specific heat jump, and superconducting coherent length. The important role of the quasi-two-dimensional flat band and the van Hove singularity are discussed in the end. |
Wednesday, March 6, 2019 4:30PM - 4:42PM |
P08.00011: Phase fluctuation in overdoped cuprates? Superconducting dome due to Mott-ness of the tightly bound preformed pairs ZIJIAN LANG, Fan Yang, Wei Ku In contrast to the current lore, we demonstrate that even the overdoped cuprates suffer from superconducting phase fluctuation in the strong binding limit. Specifically, the Mott-ness of the underlying doped holes dictates naturally a generic optimal doping around 15% and nearly complete loss of phase coherence around 25%, giving rise to a dome shape of superconducting transition temperature in excellent agreement with experimental observations of the cuprates. We verify this effect with a simple estimation using Gutzwiller approximation of the preformed pairs, obtained through variational Monte Carlo calculation. This mechanism also provides a natural explanation for the observed relation between superconducting temperature and superfluid density near the overdoped end of the dome. This realization suggests strongly the interesting possibility that the high-temperature superconductivity in the cuprates might be mostly described by Bose-Einstein condensation, without crossing over to amplitude fluctuating Cooper pairs. |
Wednesday, March 6, 2019 4:42PM - 4:54PM |
P08.00012: Angular Magnetoresistance Measurements as a Probe of the Fermi Surface in Hg1201 Katherine Schreiber, Mun Chan, Neil Harrison, Eric Bauer The Fermi surface of underdoped cuprates is reconstructed by charge density wave order. An elucidation of the exact morphology of the reconstructed Fermi-surface is expected to provide insight into the relationship between charge order and superconductivity. We present measurements of the Fermi surface of underdoped HgBa2CuO4+d (Hg1201), obtained through angular magnetoresistance. Transport along the c-axis was measured in pulsed magnetic fields of up to 65 T, applied along many polar and azimuthal angles in order to map out the Fermi surface. We discuss the implication of our measurements for the shape of the Fermi surface, including the interlayer warping, and comment on its dependence on temperature and doping. |
Wednesday, March 6, 2019 4:54PM - 5:06PM |
P08.00013: Universal T-linear resistivity and Planckian dissipation in cuprates Louis Taillefer, Anaelle Legros, Siham Benhabib, Wojciech Tabis, Francis Laliberte, Maxime Dion, Maude Lizaire, Baptiste Vignolle, David Vignolles, Hélène Raffy, ZZ Li, Pascale Auban-Senzier, Nicolas Doiron-Leyraud, Patrick Fournier, Dorothée Colson, cyril proust The perfectly linear temperature dependence of the electrical resistivity observed as T→0 in a variety of metals close to a quantum critical point is a major puzzle of condensed matter physics. Here we show that T-linear resistivity as T→0 is a generic property of cuprates, associated with a universal scattering rate [1]. We measured the low-temperature resistivity of the bi-layer cuprate Bi2212 and found that it exhibits a T-linear dependence with the same slope as in the single-layer cuprates Bi2201, Nd-LSCO and LSCO, despite their very different Fermi surfaces and structural, superconducting and magnetic properties. We then show that the T-linear coefficient (per CuO2 plane), A, is given by the universal relation A TF = h / 2e2, where e is the electron charge, h is the Planck constant and TF is the Fermi temperature. This relation, obtained by assuming that the scattering rate 1 /τ of charge carriers reaches the Planckian limit [2], whereby h /τ = 2π kBT, works not only for hole-doped cuprates but also for electron-doped cuprates, despite the different nature of their quantum critical point and strength of their electron correlations. |
Wednesday, March 6, 2019 5:06PM - 5:18PM |
P08.00014: Cuprate quantum phase transition probed by nanoscale density wave inhomogeneity Tatiana Webb, Kaylie Hausknecht, Michael C Boyer, Yi Yin, Debanjan Chowdhury, Yang He, Takeshi Kondo, Tsunehiro Takeuchi, Hiroshi Ikuta, Eric Hudson, Mohammad H Hamidian, Jennifer Hoffman The cuprate phase diagram exhibits a number of ordered phases in addition to superconductivity, and it has long been postulated that a quantum critical point - separating the notoriously unconventional underdoped regime from the overdoped so-called Fermi liquid - may influence a large region of the phase diagram. Experiments to uncover the electronic correlations giving rise to the complex phenomenology are key to understanding the complete ground state evolution. |
Wednesday, March 6, 2019 5:18PM - 5:30PM |
P08.00015: Nodeless high-Tc superconductivity in highly-overdoped monolayer CuO2 Kun Jiang, Xianxin Wu, Jiangping Hu, Ziqiang Wang We study the electronic structure and superconductivity in CuO2 monolayer grown recently on d-wave cuprate superconductor Bi2Sr2CaCu2O8+δ. Density functional theory calculations indicate significant charge transfer across the interface such that the CuO2 monolayer is heavily overdoped into the hole-rich regime. We show that both the Cu dx2−y2 and d3z2−r2 orbitals become important and the Fermi surface contains one electron and one hole pocket associated with the two orbitals respectively. The liberated low-energy d3z2−r2 band and the hole FS pocket around M enable an analogy to the multiorbital Fe-pnictides superconductors. Constructing a minimal strongly correlated two-orbital model for the eg complex, we show that the spin-orbital exchange interactions produce an intrinsic nodeless superconductor with extended s-wave pairing symmetry and a pairing energy gap comparable to the bulk d-wave gap, in agreement with recent experiments. The findings point to a direction of realizing new high-Tc superconductors over-extended doping regimes with liberated orbitals in ozone grown transition-metal-oxide heterostructures. |
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