Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session A30: Lattice Models of High-Tc Superconductors |
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Sponsoring Units: DCMP Chair: Roser Valenti, Frankfurt University Room: LACC 406B |
Monday, March 5, 2018 8:00AM - 8:12AM |
A30.00001: Doping dependence of spin modes in the Normal State of the Two-Dimensional Hubbard Model James LeBlanc , Xi Chen , Ryan Levy , Andrey Antipov , Andrew Millis , Emanuel Gull We compute spin susceptibilities in the 2D Hubbard model both at and away from half-filling for a range of correlation strengths. We use the combination of dynamical mean field theory and the dual fermion methodology to compute generalized two-particle correlated vertex functions from which we construct the spin susceiptiblity. We present results for undoped, electron and hole-doped cases and compare the results to other theoretical work and to experimental data on both insulating parent cuprates and doped materials. |
Monday, March 5, 2018 8:12AM - 8:24AM |
A30.00002: Simulation of the NMR Response of Cuprates Above and Below the Superconducting Temperature Xi Chen , Emanuel Gull , Andrew Millis Nuclear magnetic resonance (NMR) experiments play an essential role in the study of high T_{c} cuprates, showing fundamentally different features in the Knight shift and the spin-lattice relaxation rate comparing to the conventional superconductors. However, to date, the theoretical and numerical analysis of the NMR response below critical temperature is limited to RPA-based calculations or phenomenological models. Here we study the temperature and doping evolution of these quantities on the two-dimensional Hubbard model using dynamical cluster approximation with Nambu formalism. We recover the suppression of the Knight shift at the pseudogap on-set temperature and its quick decrease in superconducting region. We also simulate and analysis the spin-lattice relaxation rate and the role of vertex correction in the dynamical spin susceptibility. Both the Knight shift and the spin-lattice relaxation rate are consistent with NMR experimental results of high Tc cuprates. |
Monday, March 5, 2018 8:24AM - 8:36AM |
A30.00003: Possible limits on the Hubbard model in overdoped cuprates Yu-Jen Chen , Chih-Chung Hu , Kaung-Hsiung Wu , Chih-Wei Luo , Jenh-Yih Juang , Jenn-Min Lee , Jin-Ming Chen , Jiunn-Yuan Lin , Chia-Liang Cheng , Maw-Kuen Wu According to the recent controversial issue of the Hubbard model used in high-T_{c} cuprate systems, we have systemically measured the La_{2-x}Sr_{x}CuO_{4} (LSCO) thin films with a wide doping range of 0 ≤ x ≤ 0.4 using linear-polarized X-ray absorption spectroscopy (XAS). A rapid increase of the spectral-weight ratio of E // ab to E // c in the lowest-energy prepreak of the O K-edge XAS occurred at x > 0.18, implying that the contribution of the hole carrier was changed at high doping levels. Therefore, the influence of the apical O site in LSCO has been considered in our analysis on the estimation of the planar hole concentration (p_{pl} = p). From our recent experimental XAS results, the obtained p_{pl} values for LSCO using two referential methods provide us some comparable scales with YBCO and other hole-doped cuprates. Furthermore, the Hubbard model used in high-T_{c} cuprate systems is still applicable at higher doping than the previous report of p = 0.21, but gradually becomes more inapplicable in the heavily-doped regime. |
Monday, March 5, 2018 8:36AM - 8:48AM |
A30.00004: Fluctuating stripe order in the single-band Hubbard model for cuprates Brian Moritz , Edwin Huang , Christian Mendl , Hong-Chen Jiang , Thomas Devereaux A description of the physics associated with the cuprates must account for the translational and rotational symmetry breaking, in the form of stripes, observed in the wide array of compounds as a function of doping. We investigate the emergence of stripes in the single-band Hubbard model using determinant quantum Monte Carlo (DQMC) simulations at finite temperatures and density matrix renormalization group (DMRG) ground state calculations. Tuning the doping and model parameters, we observe and characterize the evolution of fluctuating stripes at high temperatures throughout the phase diagram, and our results demonstrate the importance of longer-range kinetic terms in fine tuning the spin incommensurability and stripe filling. |
Monday, March 5, 2018 8:48AM - 9:00AM |
A30.00005: Magnetic and Charge Order in the Three-Band Hubbard Model in the Underdoped Regime Adam Chiciak , Ettore Vitali , Hao Shi , Shiwei Zhang The Copper-Oxide planes in cuprates have been at the center of the search for a theory of high temperature superconductivity. We conduct an extensive study of the ground state of the three-band Hubbard (Emery) model, in the underdoped regime. We focus on the magnetic and charge orders. Different parameter regimes are scanned to determine the magnetic and charge properties. We present mean field results from generalized Hartree-Fock calculations on large lattice sizes, aiming to capture the different kinds of orders that are stabilized in the thermodynamic limit. The importance of the oxygen p-orbitals as charge (hole) carriers clearly emerges from our data, resulting in a much more complex phase diagram with respect to the simpler single band Hubbard model. |
Monday, March 5, 2018 9:00AM - 9:12AM |
A30.00006: Quantum Monte Carlo Calculations for the Ground State of the Three-Band Hubbard Model Ettore Vitali , Hao Shi , Adam Chiciak , Shiwei Zhang The three-band Hubbard model captures several key features of the Copper-Oxide planes in cuprate superconductors, and provides the simplest model beyond the minimal one-band Hubbard model. Recent advances in cutting-edge computational methods allow us to perform an |
Monday, March 5, 2018 9:12AM - 9:24AM |
A30.00007: Global Phase Diagram in Three Orbital Hubbard Model with Antiferromagnetic Hund Coupling Kosuke Ishigaki , Joji Nasu , Akihisa Koga , Shintaro Hoshino , Philipp Werner Alkali-doped fullerides A_{3}C_{60} have been intensively investigated as a group of compounds exhibiting high-Tc superconductivity. Recently, the possibility of the Jahn-Teller (JT) metal state was suggested experimentally in Rb_{x}Cs_{3-x}C_{60} with a face-centered cubic structure [1]. The electronic structure of this material is considered to be described by a three orbital Hubbard model with the antiferromagnetic (AF) Hund coupling. From the theoretical point of view, a spontaneous orbital-selective Mott (SOSM) state where two orbitals are Mott-insulating but the other orbital remains metallic was proposed as a new quantum state emerging in the Hubbard model [2]. This state well reproduces the properties of the JT metal realized in the Alkali-doped fullerides. Motivated by the studies, we have analyzed the ordered states of the three-orbital model with the AF Hund coupling using the dynamical mean field theory and the continuous time quantum Monte Carlo method. As a result, two different phase diagrams were obtained depending on the presence or absence of geometrical frustration. We discuss the stability and competition of quantum states such as the superconducting and SOSM states. |
Monday, March 5, 2018 9:24AM - 9:36AM |
A30.00008: d-wave pairing versus stripe order in the two-dimensional Hubbard model Mingpu Qin , Chia-Min Chung , Hao Shi , Steven White , Shiwei Zhang We study the competition between d-wave superconducting pairing and stripe orders in the ground state of the doped two dimensional Hubbard model. Two complimentary methods, the constrained path auxiliary-field quantum Monte Carlo (CP AFQMC) and Density Matrix Renormalization Group (DMRG), are employed. Pinning fields (antiferromagnetic, pairing, or both) are applied at the edge of the lattice to induce symmetry breaking in the ground state. By detailed comparisons and cross checks, we determine the ground-state properties in large rectangular supercells. Careful extrapolations to the thermodynamic limit are then performed to quantify the long-range behavior of the pairing correlation and its relation to the spin and charge order. |
Monday, March 5, 2018 9:36AM - 9:48AM |
A30.00009: Competition among superconducting, antiferromagnetic, and charge orders with intervention by phase separation in the 2D Holstein-Hubbard model Takahiro Ohgoe , Masatoshi Imada Although the electron-phonon interactions play important roles in various phenomena of condensed matter, their roles are less understood in strongly-correlated electrons such as high-T_{c} cuprates. For studies on strongly-correlated electrons, there are several numerical methods. Among them, the variational Monte Carlo (VMC) method takes the advantage of wide applicability without the notorious sign problem. Recently, we have extended this method to electron-phonon coupled systems. |
Monday, March 5, 2018 9:48AM - 10:00AM |
A30.00010: Superfluid stiffness in the 2-d Hubbard model with coexisting antiferromagnetism (AFM) and d-wave superconductivity (d-SC) Olivier Simard , Charles-David Hébert , A.-M. Tremblay , Alexandre Foley , David Sénéchal Superfluid stiffness allows a superconductor to establish phase coherence and to sustain a supercurrent. Phase coherence may occur at a lower temperature than Cooper pair formation when superfluid stiffness is small, lowering T_{c} well below its mean-field value.[1] Coexistence with other phases may also lower T_{c} in underdoped cuprates. We investigate these possibilities using cellular dynamical mean-field theory for the 2-d Hubbard model.[2] We compare the superfluid stiffness and the superconducting d-wave order parameter in the d-wave superconductor with and without coexisting antiferromagnetism. We first establish the formula that allows one to compute c-axis superfluid stiffness in the phase with coexisting antiferromagnetism and superconductivity. |
Monday, March 5, 2018 10:00AM - 10:12AM |
A30.00011: Multistage CDW Transitions in Cuprate High-T_{c} Superconductors: Functional-Renormalization-Group Analysis Hiroshi Kontani , Masahisa Tsuchiizu , Kouki Kawaguchi , Youichi Yamakawa Recently, complex phase transitions accompanied by the rotational symmetry breaking have been discovered experimentally in cuprate superconductors. To understand the origin of the symmetry breaking, we study various charge susceptibilities in an unbiased way, by applying the functional-renormalization-group method to the realistic d-p Hubbard model [1]. Without assuming the wavevector of the order parameter, we reveal that the most dominant instability is the uniform (q = 0) charge density wave (CDW) on the p orbitals, which possesses the B_{1g} symmetry. This uniform CDW triggers another nematic p-orbital CDW along the axial (Cu-Cu) direction at Q_{a} = (π/2,0). It is predicted that uniform CDW is driven by the spin fluctuations in the pseudogap region, and another CDW order at q = Q_{a} is triggered by the uniform order. The predicted multistage CDW transitions are caused by the Aslamazov-Larkin-type fluctuation-exchange processes. We also revealed that the B_{2g} symmetry CDW emerges when the density of states near the hot-spots is strongly suppressed by the strong correlation effect. [1] M. Tsuchiizu et al., arXiv:1705.05356; K. Kawaguchi et al., 86, 063707 (2017). |
Monday, March 5, 2018 10:12AM - 10:24AM |
A30.00012: Possibility of d + is superconductivity in t-J model: Implications for cuprate high-T_{c} superconductors Aabhaas Mallik , Gaurav Gupta , Vijay Shenoy , Hulikal Krishnamurthy Early experiments on high-T_{c} cuprate superconducors found that the superconducting state in these systems do not break time reversal symmetry, and, they have Cooper pairs with predominantly d-wave pairing symmetry. With the improved experimental techniques, the applicability of these findings over the entire superconducting domain have come to be questioned. Recent ARPES studies provide substantial evidence for node-less superconductivity in cuprates at very low doping. At the same time, convincing evidence for Kerr rotation coinciding with the onset of charge density wave ordering has been provided by Karapetyan et al. Here, we present results demonstrating that, within the slave-boson formulation of the t-J model, the d-wave superconductor (d-SC) is unstable at low doping to its anti-symmetric phase mode fluctuations when the effect of fluctuations is treated self-consistently. We then show that this instability gives way to a time reversal symmetry broken d + is-SC in the underdoped region. Finally, we discuss how this physics might be relevant for understanding the recent experiments on cuprates described above. |
Monday, March 5, 2018 10:24AM - 10:36AM |
A30.00013: Relationship Between the Doping-induced States and the Magnetically Excited States at the Mott Transition Masanori Kohno The relationship between the doping-induced states in the single-particle spectrum in the small-doping limit and the magnetically excited states of a Mott insulator is investigated based on their quantum numbers and overlaps [1,2]. By using the t-J ladder model, the relationship is explicitly illustrated [1]. The results imply that the Mott transition is characterized by freezing of the charge degrees of freedom while the spin degrees of freedom remain active, which is consistent with the results for the Mott transition in the one- and two-dimensional Hubbard and t-J models [2--5]. |
Monday, March 5, 2018 10:36AM - 10:48AM |
A30.00014: Study of the Two Dimensional Holstein Model using Determinant Quantum Monte Carlo and Migdal-Eliashberg Theory. Philip Dee , Ken Nakatsukasa , Yan Wang , Benjamin Nosarzewski , Edwin Huang , Thomas Devereaux , Steven Johnston The simplest model for studying electron-phonon coupling in many body systems is the singleband Holstein model. Most studies that utilize this model examine the nature of charge-density and pairing correlations at or around half-filling, but no comprehensive calculation for the dependence of the critical temperatures T_{c}^{ SC} , T_{c}^{ CDW} on the electron occupancy 〈n〉 far away from half-filling seems to exist in the literature. Furthermore, many of these studies compare results from quantum Monte-Carlo (QMC) to Migdal-Eliashberg (ME) theory in an attempt to shed light on the importance of the vertex corrections neglected in ME theory. In this presentation, we will show results highlighting the ME theory phase diagram with respect to 〈n〉over multiple phonon frequencies Ω_{ph} using relatively large lattice sizes. Moreover, we will also compare DQMC against ME theory on smaller lattices across a wide range of 〈n〉 and for multiple phonon frequencies. The corresponding ME theory results are found to be comparable to the numerically exact DQMC for lower occupancies (〈n〉≤0.4 ). Lastly, we will discuss the implications of these findings for superconductors with low numbers of charge carriers. |
Monday, March 5, 2018 10:48AM - 11:00AM |
A30.00015: Pairing correlation near Kondo-destruction quantum criticality Ang Cai , Jed Pixley , Kevin Ingersent , Qimiao Si How quantum criticality affects superconductivity is a central issue in strongly correlated systems. Particularly pressing is for the beyond-Landau quantum criticality, such as appearing in heavy fermion systems in the form of Kondo destruction [1]. In addition, the superconducting Tc in systems such as Ce-115 is high as measured by the Fermi temperature. Thus motivated, we address the pairing instabilities near a Kondo destruction quantum critical point (QCP). We study the cluster Bose-Fermi Anderson model and, using the Cluster Extended-DMFT approach, the Anderson lattice model. We have identified a Kondo destruction QCP between a heavy Fermi liquid and an antiferromagnetic metal phase, and demonstrated enhanced pairing correlations in its vicinity [2]. We also analyze the dependence of this effect on the spin anisotropy. Implications of our results for Ce-115 systems is discussed. |
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