Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session B41: Theory of Superconducting Cuprates |
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Sponsoring Units: DCMP Chair: Brian Moritz, SLAC Room: 388 |
Monday, March 13, 2017 11:15AM - 11:27AM |
B41.00001: Impact of nearest-neighbor repulsion on superconducting pairing in 2D extended Hubbard model Mi Jiang, U.R. Hahner, T.A. Maier, T.C. Schulthess Using dynamical cluster approximation (DCA) with an continuous-time QMC solver for the two-dimensional extended Hubbard model, we studied the impact of nearest-neighbor Coulomb repulsion $V$ on d-wave superconducting pairing dynamics. By solving Bethe-Salpeter equation for particle-particle superconducting channel, we focused on the evolution of leading d-wave eigenvalue with $V$ and the momentum and frequency dependence of the corresponding eigenfunction. The comparison with the evolution of both spin and charge susceptibilities versus $V$ is presented showing the competition between spin and charge fluctuations. [Preview Abstract] |
Monday, March 13, 2017 11:27AM - 11:39AM |
B41.00002: Universal superconducting gap to $T_c$ ratio in the extended Hubbard model A. Reymbaut, M. Charlebois, M. Fellous-Asiani, L. Fratino, P. Semon, G. Sordi, A.-M. S. Tremblay The universal ratio of the superconducting gap to transition temperature $T_c$ has been one of the key successes of BCS theory. The explanation of the deviations from this ratio at strong electron-phonon coupling in turn confirmed the Eliashberg extension of BCS [1]. Recent "tomographic density of states" (TDoS) ARPES data on Bi2212 suggest that this ratio deviates strongly from the expectations of both approaches in cuprates [2]. We extract this ratio from cellular dynamical mean-field theory (CDMFT) calculations for the extended Hubbard model with a continuous-time quantum Monte Carlo solver and compare it with experiment. The result gives a universal behavior for this ratio as a function of doping over a wide range of values of the local and first-neighbor interactions. In addition, we compare the relation between the gap and the order parameter at low temperature with the Gutzwiller approach of YRZ [3]. This comparison is extended to a few zero-frequency quantities related to the pairing dynamics and extracted with the MaxEntAux method [4,5]. [1] J. P. Carbotte, RMP 62, 1027–1157 (1990) [2] T. J. Reber et al., arXiv:1508.06252 (2015) [3] K.-Y. Yang et al., PRB 73, 174501 (2006) [4] A. Reymbaut et al., PRB 92, 060509(R) (2015) [5] A. Reymbaut et al., PRB 94, 155146 (2016) [Preview Abstract] |
Monday, March 13, 2017 11:39AM - 11:51AM |
B41.00003: Signatures of Quasiparticle Interference from Random Disorder in High-Temperature Superconductors Miguel Sulangi, Jan Zaanen We obtain real-space and Fourier-transformed maps of the local density of states of the cuprates for various kinds of disorder. We consider point-like impurities; smooth, ``Coulombic'' disorder; and disorder arising from random hoppings, on-site energies, and superconducting gaps. For the case of multiple point-like impurities it is found that its Fourier-transformed LDOS resembles that of a single point-like scatterer, but with additional noise. Disorder from a large number of randomly placed smooth potential scatterers gives rise to stripe-like patterns in the real-space LDOS, while its Fourier-transformed map reveals that small momenta in the nodal directions dominate scattering processes at low energies. The cases of disorder from random hoppings, on-site potentials, and gaps are studied, and it is shown that their Fourier-transformed maps are qualitatively different. We explore the possibility that smooth-potential and random disorder might explain the stripe-like patterns seen in STM studies. We also apply this analysis to a variety of proposed ground states of the cuprates with coexisting order. [Preview Abstract] |
Monday, March 13, 2017 11:51AM - 12:03PM |
B41.00004: Pseudogap and kinetic energy of unconventional superconductivity in the two dimensional Hubbard model. A. Troper, Eleonir Calegari, Ana Lausmann, Leonardo Prauchner, Sergio Magalhaes, C. M. Chaves In conventional superconductors the transition from the normal to the superconducting state is accompanied by a reduction in the potential energy and an increase in the kinetic energy. On the other hand, in HTSC the potential and the kinetic energies present an unconventional behavior that may be strongly related to the pseudogap phenomena. In this work, we analyze the kinetic and potential energies in the superconducting state of the two-dimensional Hubbard model [1,2]. The model is investigated by the Green's function method within a n-pole approximation, which allows to consider superconductivity with $d_{x2-y2}$-wave pairing. In the present scenario, a pseudogap emerges near the anti-nodal points in the Fermi surface, when the strong coupling regime is reached. The obtained results show that in the low doping region, the system enters the strong coupling regime and the opening of a pseudogap is followed by a decreasing in the kinetic energy and a increasing in the potential energy. [1] L. M. Roth, Phys. Rev. 184, 451 (1969). [2] J. Beenen and D. M. Edwards, Phys. Rev. B52, 13636 (1995).. [Preview Abstract] |
Monday, March 13, 2017 12:03PM - 12:15PM |
B41.00005: Ground-state properties of the three-band Hubbard model Shiwei Zhang, Ettore Vitali, Adam Chiciak, Hao Shi The three-band Hubbard model proposed by Emery describes the CuO$_2$ plane in cuprate superconductors by retaining both Cu and O orbitals in a minimal sense. Applying the latest developments in the auxiliary-field quantum Monte Carlo (AFQMC) method, we investigate ground-state properties of this model at half-filling and when lightly (under-)doped. The AFQMC uses generalized Hartree-Fock (GHF) trial wave functions to control the sign problem. A self-consistent constraint \footnote{M.\ Qin, H.\ Shi, S.\ Zhang, arXiv:1608.07154 (2016).} is applied. We also determine the unrestricted Hartree-Fock (UHF) and GHF ground states and compare their predictions with those from AFQMC. Similarities and differences between the three-band model and one-band Hubbard model will be discussed. [Preview Abstract] |
Monday, March 13, 2017 12:15PM - 12:27PM |
B41.00006: Unusual behavior of Superfluid Density of Overdoped Cuprates Aabhaas V. Mallik, Vijay B. Shenoy, H. R. Krishnamurthy We theoretically study the superfluid density of overdoped cuprate superconductors within a t-J like model. We show that the temperature dependence of the superfluid density on the overdoped side has very unusual features. We explain the physical origins of this behavior, and show that this can be used to understand the recent experimental results of Bozovic et. al. [Nature 536, 309 (2016)]. [Preview Abstract] |
Monday, March 13, 2017 12:27PM - 12:39PM |
B41.00007: Enhancement mechanisms of two-particles exchange scattering processes in single-layer cuprate superconductors Shingo Teranishi, Satoaki Miyao, Kazutaka Nishiguchi, Koichi Kusakabe To estimate effective in-plane exchange interactions of a CuO$_2$ layer, we applied self-consistent exact-exchange calculations for several single-layered cuprate superconductors, and explored material dependence of the effective super-exchange processes mediated by all relevant orbitals of the real materials. The effective exchange is enhanced owing to low-lying energy levels originated from the buffer layers of Hg1201 ($T_C\simeq$100K), while the effect is smaller for Tl1201 ($T_C\simeq$50K) than mercury compounds. The case of the Tl2201 is intermediate. The effective exchange is relevant in the strong-correlation mechanism of the superconductivity in cuprate, which may reveal the material dependence found in real experiments. [Preview Abstract] |
Monday, March 13, 2017 12:39PM - 12:51PM |
B41.00008: Understanding the Superconducting Properties of YBa$_{\mathrm{2}}$Cu$_{\mathrm{3}}$O$_{\mathrm{7}}$ from First-Principles Guang-Lin Zhao The observation of high $_{\mathrm{Tc}}$ value and an anomalously small isotope effect in YB$_{\mathrm{a2}}$Cu3O7 (YBCO) created a great challenge for understanding In order to shed some light on the problem, we integrated the first-principles calculation of electronic structure of the material into the theory of many-body physics for superconductivity and studied the superconducting properties of YBCO. We used two approaches: (1) the generalized Tc equation developed by Abrikosov et al; and (2) the four-dimensional Eliashberg gap equation of strong coupling theory.It is demonstrated from first-principles that the sharp electronic structure around the Fermi level in YBCO, due to extended saddle point singularity, strongly correlate with the anomalous isotope effect in this superconductor. The high Tc value in YBCO around 90 K may mostly be attributed to the high electron density of states (DOS) around Fermi level and high phonon energy in the material. Some experimental evidences including photoemission spectroscopy measurements are also discussed.The work was funded in part by ARO (Award {\#} W911NF-15-1-0483). [Preview Abstract] |
Monday, March 13, 2017 12:51PM - 1:03PM |
B41.00009: Mott-Slater transition in undoped cuprates Robert Markiewicz, Gianina Buda, Peter Mistark, Chris Lane, Arun Bansil We study phases of short-range magnetic order by coupling different density-wave modes with a self-consistent vertex correction. By tuning the band structure we are able to transform between different cuprates, finding a transition between order driven by conventional Fermi-surface nesting and order driven by Van Hove nesting. While the former describes an incommensurate Slater spin-density wave, the latter represents a Mott $(\pi,\pi)$ antiferromagnet, where the Fermi surface plays only a minor role. While most cuprates fall on the Slater-side of the transition, La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) lies just on the Mott side. Remarkably, just at the transition there is an emergent spin-liquid phase, which may play a role in the LSCO phase diagram. [Preview Abstract] |
Monday, March 13, 2017 1:03PM - 1:15PM |
B41.00010: Fluctuation Maps of Competing Order in Cuprates Peter Mistark, Robert Markiewicz, Ioana Buda, Christopher Lane, Arun Bansil We demonstrate how the density-functional-based Lindhard susceptibility can be used to probe the origin of the cuprate pseudogap. To start we create maps, in doping vs temperature space, of a class of momentum vectors at which the susceptibility is maximum, called fluctuation maps. These maps clearly show how closely related different materials are and allow us to sort materials into equivalence classes with topologically equivalent fluctuation maps. From these classes, we can chose ‘reference families’, which depend on a minimal number of hopping parameters. This allows us to tune between different cuprates by varying just a single parameter. Using these concepts, we show how the pseudogap is controlled by bosonic entropy, and how this is encoded in the susceptibility. Our analysis reveals one last surprise: the VHS plays an important role in entropic effects, and in turn the physics of the VHS is strongly entwined in pseudogap physics. Work supported by U.S. Department of Energy. [Preview Abstract] |
Monday, March 13, 2017 1:15PM - 1:27PM |
B41.00011: Superconductivity mediated by quantum critical antiferromagnetic fluctuations: the rise and fall of hot spots Xiaoyu Wang, Yoni Schattner, Erez Berg, Rafael Fernandes The maximum transition temperature T$_{c}$ observed in the phase diagrams of several unconventional superconductors takes place in the vicinity of a putative antiferromagnetic quantum critical point. This observation motivated the theoretical proposal that superconductivity in these systems may be driven by quantum critical fluctuations, which in turn can also promote non-Fermi liquid behavior. In this talk, we present a combined analytical and sign-problem-free Quantum Monte Carlo investigation of the spin-fermion model -- a widely studied low-energy model for the interplay between superconductivity and magnetic fluctuations. By engineering a series of band dispersions that interpolate between near-nested and open Fermi surfaces, and by also varying the strength of the spin-fermion interaction, we find that the hot spots of the Fermi surface provide the dominant contribution to the pairing instability in this model. We show that the analytical expressions for T$_{c}$ and for the pairing susceptibility, obtained within a large-N Eliashberg approximation to the spin-fermion model, agree well with the Quantum Monte Carlo data, even in the regime of interactions comparable to the electronic bandwidth. [Preview Abstract] |
Monday, March 13, 2017 1:27PM - 1:39PM |
B41.00012: The effect of charge transfer fluctuation on superconductivity in high temperature superconductors YiHsuan Liu, Huan-Kuang Wu, Ting-Kuo Lee $High-T_c$ Cuprates have been studied quite often as an effective one band $t-J$ model that neglects charge fluctuation between oxygen $2p^6$ band and copper $3d^{10}$ band, and Zhang-Rice singlet is just a hole in the model. However, recent Scanning Tunneling Spectra(STS) measurement on underdoped Cuprate shows that charge transfer gap is only of order $1~2$ eV. This small gap necessitates a re-examination of the charge transfer fluctuation. Here we modify the t-J model by including charge transfer fluctuation allowing the formation of doubly occupied sites. For certain parameters it is similar with the t-J-U model. This model is studied via variational Monte Carlo method(VMC). Our result shows that this model can give a unified behavior of superconducting dome with different long rang hopping parameters. The anti-correlation between charge transfer gap and pairing is also confirmed. More interestingly the charge fluctuation is found to affect pairing order parameter in different ways in underdoped and overdoped regions. [Preview Abstract] |
Monday, March 13, 2017 1:39PM - 1:51PM |
B41.00013: Thermodynamic critical field and Upper critical field of underdoped YBa$_2$Cu$_3$O$_{6+x}$ cuprates PATRICIA SALAS, M. A. SOLIS, M. FORTES In the frame of the Layered Boson-Fermion superconductivity model applied to cuprate superconductors, we obtain the condensation energy, the thermodynamic critical field and the upper critical field for underdoped cuprate superconductors YBa$_2$Cu$_3$O$_{6+x}$, with $x \in [0.55,0.9]$ ranging from underdoped to optimally doped. The only two parameters of the system, which are the impenetrability of the planes and the paired fermion fraction below the critical temperature $T_c$, are uniquely determined by minimizing the Helmholtz free energy and fixing the experimental critical temperature. We compare our results for {\it a)} the thermodynamic critical field and the upper critical field as functions of temperature for several doping values, and {\it b)} the thermodynamic critical field and the upper critical field for $T = 0$ as functions of doping, with experimental data and show they are in very good agreement. \noindent [1] P. Salas, M. Fortes, M. A. Solis and F. J. Sevilla, Physica C {\bf 534}, 37 (2016). \noindent [2] P. Salas, M. A. Solis, M. Fortes and F. J. Sevilla, submited to Int. Jou. Mod. Phys. B. [Preview Abstract] |
Monday, March 13, 2017 1:51PM - 2:03PM |
B41.00014: Two-Particle Self-Consistent Analysis for the Electron-Hole Asymmetry of Superconducting Transition Temperature in High-$T_{c}$ Cuprates Daisuke Ogura, Kazuhiko Kuroki The striking electron-hole doping asymmetry in the doping dependence of $T_{c}$ is among unsolved issues in the study of the high-$T_{c}$ cuprate superconductors. It is well-known that in the hole-doped case, $T_{\mathrm{c\thinspace }}$exhibits a dome-like feature against the doping rate. On the other hand, $T_{\mathrm{c\thinspace }}$in the electron-doped systems monotonically increases as the doping is reduced, at least down to a very small doping rate$^{\mathrm{\thinspace [1,2]}}$. To understand the origin of this electron-hole asymmetry of $T_{\mathrm{c}}$, we perform the Two-Particle Self-Consistent (TPSC) analysis$^{\mathrm{\thinspace [3]}}$ for the three-band $d-p$ model constructed from the first principles calculation $^{\mathrm{[4]}}$. The obtained doping dependence reproduces the asymmetric behavior of $T_{\mathrm{c}}$. This is explained as a combined effect of the intrinsic electron-hole asymmetry in systems comprising Cu3$d$ and O2$p$ orbitals and the band-filling-dependent vertex correction. References: [1] M. Brinkmann, et al., Phys. Rev. Lett. \textbf{74}, 4927 (1995). [2] A. Tsukada, et al., Solid State Commun. \textbf{133},427 (2005). [3] Y. Vilk and A.-M. Tremblay, J. Phys. I (France) \textbf{7}, 1309 (1997). [4] A. A. Mostofi, et al., Phys. Commun.\textbf{ 178}, 685 (2008). [Preview Abstract] |
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