Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C09: Superconductivity: Copper Oxide - TheoryFocus
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Michael Sentef, Max Planck Institute for the Structure and Dynamics of Matter Room: BCEC 151A |
Monday, March 4, 2019 2:30PM - 2:42PM |
C09.00001: Numerical study of the momentum and doping dependence of "hot spots" and single-particle spectra in electron-doped cuprates Brian Moritz, Yao Wang, Edwin Huang, Thomas Devereaux We present a systematic study of the single-particle spectral function in electron-doped cuprates determined from state-of-the-art numerical calculations using cluster perturbation theory. By comparing the appearance of the "hot spots" as a function of momentum and electron filling, we conclude that the Hubbard model with an intermediate interaction U can well capture recent experimental observations from photoemission in Nd2-xCexCuO4. This work suggests that microscopic mechanisms similar to the hole-doped cuprates may drive the short-ranged anti-ferromagnetism, and ultimately superconductivity, even on the electron doped side, and set the stage for further theoretical explorations. |
Monday, March 4, 2019 2:42PM - 2:54PM |
C09.00002: Phenomenological Theory for Pseudogap and Superconducting Phases of High-Temperature Superconductors Jianhao Zhang, Sen Li, Yao Ma, Zheng-Yu Weng We present a phenomenological Green's function to characterize the superconducting and pseudogap phases of the cuprates based on a microscopic theory of doped Mott insulators. In this framework, the ``Fermi arc'' and ``superconducting kink'' phenomena in ARPES experiments can be systematically obtained as a function of doping. We demonstrate that the phase-string-induced fractionalization plays a crucial role in leading to this exotic Green's function paradigm. |
Monday, March 4, 2019 2:54PM - 3:06PM |
C09.00003: Intrinsic Pair Density Waves in CDMFT Improve Agreement with Cuprates Simon Verret, Alexandre Foley, Jyotirmoy Roy, Maxime Charlebois, David Senechal, Andre-Marie Tremblay Cluster dynamical mean-field theory (CDMFT) is one of the most successful methods to treat strongly correlated electrons systems. It is well known, however, that CDMFT leads to an artificial breaking of translational invariance. Here, we investigate how this manifests itself. We report artificial density waves taking the shape of the cluster (cluster density waves) in all our CDMFT solutions. In particular, we report pair density waves in the superconducting solution. We discuss how these artificial density waves help the agreement of CDMFT with the low-energy spectra of cuprate high temperature superconductors. Namely, we find subgap structures similar to those found in tunnelling experiments and a related separation between nodal and anti-nodal gaps in the spectral weight, as observed in photoemission experiments. This agreement with cuprates suggests that spatial inhomogeneity is an important ingredient to explain the low-energy spectrum of cuprates, even in the strongly correlated case. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C09.00004: FLEX+DMFT approach for superconductivity in multi-band systems: A study on bilayer Hubbard model Daisuke Ogura, Kazuhiko Kuroki Broadly speaking, to enhance the superconducting transition temperature Tc, a strong paring interaction and a light electron effective mass are favorable. However, the strong pairing interaction not only enhance superconductivity, but also results in the strong quasi-particle renormalization in general. As a way to circumvent this dilemma, we can consider the multi-band Hubbard model as discussed in the previous studies [1, 2]. In multi-band systems, spin fluctuations with finite energy arising from interband scattering channels can develop and act as an effective pairing interaction. Finite energy fluctuations do not cause an abovementioned strong competition between the quasi-particle renormalization and superconductivity. To treat both local and non-local correlations, we have applied the FLEX (fluctuation exchange) + DMFT (dynamical mean-field theory) method [4, 5] to the bilayer Hubbard model. In the presentation, we will discuss the correlation effects and the superconductivity arising from the interband pair scattering. |
Monday, March 4, 2019 3:18PM - 3:30PM |
C09.00005: Enhancement of d-wave Pairing in Cuprates by Electron-phonon Couplings Xun Cai, Zixiang Li, Hong Yao The high-temperature cuprate superconductors have attracted great attentions over the past few decades. Since its discovery, the role of electron-phonon couplings in the mechanism of high-temperature superconductivity in cuprates has been intensely debated. Some believe that electron-phonon coupling may have a key impact on the d-wave superconductivity in cuprates. We study the microscopic model of electrons on the 2D square lattice with both electron-electron and electron-phonon interactions. From determinant quantum Monte Carlo simulations (DQMC), we show that d-wave pairing can be significantly enhanced when the electron-phonon coupling is increased. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C09.00006: Quantifying Quantum Order Transitions in Cuprate High-Tc Superconductor Zhen-Su She, Rong Li Wall turbulence and cuprates HTSC are similar for they are both complex systems with many degrees of freedom, and in non-equilibrium state with strong fluctuations. Here, we identify a new similarity between the two: both display symmetry-breaking transition embedded in nontrivial transport. First, we present a recent structural ensemble dynamics (SED) theory of wall turbulence that yields unified and accurate description of mean velocity and turbulent intensities profiles across the entire domain of turbulent boundary layer, using a multi-layer formula of a length order function quantifying turbulent eddy size (She et al., JFM, 2017,2018). Then, we extend the SED theory to cuprates HTSC to predict a similar length order function, which successfully describes transitions between several dominant quantum orders such as spin order, charge order and superconductivity, as validated by resistivity data (see also another contributed talk, Li and She, 'New mechanism of umklapp scattering in cuprate HTSC' ). We conclude that wall turbulence and cuprates HTSC share similar self-organized symmetry-breaking feature, which can be effectively described through length order function. |
Monday, March 4, 2019 3:42PM - 3:54PM |
C09.00007: Instabilities of Bogoliubov-de Gennes quasiparticles in the zeroth Landau level of nodal superconductors under strain Emilian Nica, Onur Erten Landau levels have recently been predicted [1-2] to emerge in 2D nodal superconductors under applied strain or doping gradients. In contrast to more conventional cases, time-reversal symmetry is preserved in the absence of interactions. We study the interaction-driven instabilities of the Bogoliubov-de Gennes quasiparticles in the flat, zeroth Landau-level. We focus on ferromagnetic and valley-polarized states and show that the resulting phase diagram depends on the direction of the applied strain. |
Monday, March 4, 2019 3:54PM - 4:06PM |
C09.00008: Projected BCS theory for high-temperature superconductivity HyunWoong Kwon, Kwon Park At the core of the problem of high-temperature superconductivity lies the relationship between strong correlation and superconductivity. One of the most exciting prospects on their relationship is that strong correlation is the very source of high-temperature superconductivity. To investigate the validity of this prospect, we perform a variational analysis of the BCS model Hamiltonian projected onto the constrained Hilbert space with infinitely strong correlation, or no double occupancy. This is also known as the Gutzwiller projection. For convenience, let us call such an analysis the projected BCS theory. By computing the overlap between the exact ground states of the projected BCS theory and those of the t-J model via exact diagonalization, here, we show that the projected BCS theory provides excellent variational states for the ground states of the t-J model in the entire range of hole concentration including both half filling and finite doping. It is emphasized that the resonating valence bond (RVB) state, i.e., the projected BCS wave function is closely related to the ground state of the projected BCS theory, while quite different at low doping. What makes the difference is whether the projection is applied to the ground state of the Hamiltonian or the Hamiltonian itself. |
Monday, March 4, 2019 4:06PM - 4:18PM |
C09.00009: ABSTRACT WITHDRAWN
|
(Author Not Attending)
|
C09.00010: Vortex structure and Hall conductivity in d-wave superconductors Vladimir Kalnitsky, Netanel Lindner, Erez Berg, Sebastian D Huber The Hall conductivity σxy serves as an important experimental probe for determining the sign of charge carriers in materials. In type II superconductors models of vortex dynamics predicted σxy to have the same sign as in the normal state; that is, the same as the charge carriers. However, Hall measurements showed that σxy changes sign as a function of temperature in YBCO and other cuprates, in contradiction to these predictions. Recently it was shown that a sign reversal of σxy occurs in a generic model for an s-wave superconductor, due to a topological transition in the vortex core. We show that a similar effect occurs in a model for a d-wave superconductor, and find a rich phase diagram of σxy as a function of interaction strength and doping p: in addition to a sign reversed phase, we find a phase in which σxy ∼ p . While such a relation implies a small Fermi surface, the model does not exhibit a bulk Fermi surface reconstruction. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C09.00011: Electronic States Induced by Doping a Mott Insulator in the Presence of Antiferromagnetic Order Masanori Kohno Recent theoretical studies on the Mott transition suggest that magnetically excited states emerge in the Mott gap in the single-particle spectrum with the dispersion relation shifted by the Fermi momenta following the doping of a Mott insulator [1--4]. This characteristic is difficult to explain in terms of mean-field quasiparticles in antiferromagnetic order. Here, by taking into account spin fluctuation in the random-phase approximation, electronic states exhibiting momentum-shifted spin-wave dispersion relation are shown to emerge in the Mott gap following the doping of a Mott insulator even though antiferromagnetic order persists [5]. The results imply that the emergence of electronic states exhibiting momentum-shifted magnetic dispersion relation is a general and fundamental characteristic of the Mott transition regardless of whether antiferromagnetic order exists or not. |
Monday, March 4, 2019 4:42PM - 4:54PM |
C09.00012: High Tc superconductivity in strong electron-phonon interacting systems with frustrated charge order Zixiang Li, Marvin L Cohen, Dunghai Lee In this talk, I will discuss how geometric frustration inhibits charge order and allows superconductivity to benefits from strong electron-phonon coupling. We perform sign-problem-free Quantum Monte Carlo simulation to study Holstein model with strong electron-phonon coupling on triangular and square lattices. Our simulation indicates that geometric frustration of charge density wave enables strong superconductivity to exist under much wider conditions in temperature and electron-phonon coupling strength. In particular, under geometric frustration a novel coexistence phase where superconducting coherence develops within a charge ordered state exists in a strong electron-phonon coupling regime. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C09.00013: Continuing search for the origin of HTSC: DFT studies of selected copper oxide proxy structures reviewed and paths forward suggested Paul Grant In this presentation, we review our past attempts to uncover the pairing mechanism underlying high temperature superconductivity in copper oxide compounds and suggest possible paths forward.1, 2 One such path would be to derive and generalize pairing coupling functions to apply to DFT + U computed eigenstates in order to estimate Cooper pair coupling strengths arising from a combination of both lattice and spin excitations. Interestingly, such interactions were found in transition metal alums some 78 years ago as manifested in linking their respective Debye and Curie temperatures.3 We suggest repeating such experiments today on the copper oxide compounds as a function of hole/electron concentration, along with a possible computational strategy to pursue in the interpretation of the results4 to finally resolve the fundamental origin of high temperature superconductivity. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C09.00014: Singlet s±-wave pairing in quasi-one-dimensional ACr3As3 (A=K, Rb, Cs) superconductors Li-Da Zhang, Xiaoming Zhang, Juan-Juan Hao, Wen Huang, Fan Yang The recent discovery of quasi-1D Cr-based superconductivity has generated much excitement. We study in this work the superconducting instabilities of a representative compound, the newly synthesized KCr3As3 superconductor. Based on inputs from DFT calculations, we first construct an effective multi-orbital TB Hamiltonian to model its low-energy band structure. We then employ standard RPA calculations to investigate the superconducting instabilities of the resultant multi-orbital Hubbard model. We find the leading pairing symmetry realized in this material is singlet s±-wave pairing. This singlet pairing is driven by spin-density wave fluctuations enhanced by FS. We design a phase-sensitive measurement to identify the s-wave pairing. The s±-wave pairing in KCr3As3 shall also exhibit a subgap spin resonance mode near the nesting vector, which can be tested by inelastic neutron scattering measurements. We also propose further application of KCr3As3 by utilizing it to induce TRI TSC via proximity effect. Our study shall be of general relevance to all superconductors in the family of ACr3As3 (A=K, Rb, Cs). Reference: arXiv: 1809.07117 |
Monday, March 4, 2019 5:18PM - 5:30PM |
C09.00015: Superconductivity in systems exhibiting the Altshuler-Aronov anomaly Richard Hlubina, Branislav Rabatin Dirty superconductors close to the metal-insulator transition frequently exhibit a pseudogap in the normal state due to the Altshuler-Aronov (AA) effect. In this talk we show that, making use of generalized Eliashberg equations, the AA effect and superconductivity can be described on equal footing. We derive explicit expressions for the Coulomb pseudopotential in 3D, taking into account also the anomalous diffusion. We present a full numerical solution for two normal-state and two anomalous self-energies. In the normal state, we amend the known results for the purely electronic AA effect; with electron-phonon coupling turned on, we find additional anomalies in the density of states close to the phonon energy. We study how the critical temperature and density of states of strongly disordered 3D superconductors change with normal-state resistivity. We find that the type of transition from the superconducting to the insulating state depends on the strength of electron-phonon coupling: at weak coupling there exists an intermediate normal state, whereas at strong coupling the transition is direct. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700