Bulletin of the American Physical Society
APS March Meeting 2021
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session M47: Superconductivity Theory: Cuprates and doped spin liquidsLive

Hide Abstracts 
Sponsoring Units: DCMP Chair: Benjamin Fregoso, Kent State University 
Wednesday, March 17, 2021 11:30AM  11:42AM Live 
M47.00001: Superconductivity and doping on oxygen in the three band model Nicolas KOWALSKI, A.M. S. Tremblay, patrick Sémon Recent experimental results  using NMR measurements  have shown, across the cuprates [1], that the maximum critical temperature is much more strongly correlated with doping on the oxygen than with total doping. Using the CDMFT approximation and a finite temperature CTHYB impurity solver, we investigate the phase diagram of the threeband Hubbard model in order to reproduce those results with theoretical means. Although the correlation is not perfect, we found such a trend, first focusing on the superconducting orderparameter and then on the critical temperature. We also discuss correlations between the spin susceptibilities and order parameter and a regime of parameters with a coexistence between pseudogap and superconducting phase. 
Wednesday, March 17, 2021 11:42AM  11:54AM Live 
M47.00002: Optimizing superconductivity in the threeband Hubbard model Sidhartha Dash, David Senechal We explore the phase diagram of the threeband Hubbard model for highT_{c} cuprates using Cluster Dynamical Mean Field Theory at zero temperature with an exact diagonalization solver. Our goal is to maximize the superconducting order parameter and identify the model characteristics that most enhance superconductivity. We start with realistic values of the band parameters from Weber et al [1]. We observe that the order parameter at optimal doping is monotonously related to the oxygen doping and the chargetransfer gap. We also find a marked correlation of the order parameter at optimal doping with the occupation of the upper Hubbard band. We report on the correlation of the maximum order parameter with other characteristics of the model, such as the spin susceptibility etc. 
Wednesday, March 17, 2021 11:54AM  12:06PM Live 
M47.00003: Orbital structure of the effective pairing interaction in the hightemperature superconducting cuprates Peizhi Mai, Giovanni Balduzzi, Steven S. Johnston, Thomas Maier The nature of the effective interaction responsible for pairing in the hightemperature superconducting cuprates remains unsettled. This question has been studied extensively using the simplified singleband Hubbard model, which does not explicitly consider the orbital degrees of freedom of the relevant CuO_2 planes. Here, we use dynamic cluster approximation to study the orbital structure of the pairing interaction in the threeband Hubbard model, which treats the orbital degrees of freedom explicitly. We find that the interaction predominately acts between neighboring copper orbitals, but with significant additional weight appearing on the surrounding bonding molecular oxygen orbitals. By explicitly comparing these results to those from the simpler singleband Hubbard model, our study provides strong support for the singleband framework for describing superconductivity in the cuprates. 
Wednesday, March 17, 2021 12:06PM  12:18PM Live 
M47.00004: Cooperative enhancement of superconducting pairing at quarter filling by electronelectron and electronphonon interactions Dipayan Roy, R. Torsten Clay Unbiased numerical calculations within twodimensional Hubbard models have found no evidence for longrange superconducting order. This suggests that repulsive interactions between electrons alone are not sufficient to realize superconductivity and other interactions are required. The most likely candidate is the electronphonon interaction. However, existing theories of superconductivity emphasize either electronelectron or electronphonon interactions, each of which tends to cancel the effect of the other. We present direct evidence from quantum Monte Carlo calculations of cooperative, as opposed to competing, effects of electronelectron and electronphonon interactions within the frustrated Hubbard Hamiltonian, uniquely at the bandfilling of onequarter[1]. Bondcoupled phonons and the onsite Hubbard U cooperatively 
Wednesday, March 17, 2021 12:18PM  12:30PM Live 
M47.00005: Normal charge densities in cold quantum critical superfluids Eric Mefford, Blaise Gouteraux Recent experiments on overdoped LSCO by Bozovic et al. [Nature 536, 282 (2016)] have revealed an anomalously low superfluid density. Further measurements by Mahmood et al. [PRL 122, 027003 (2019)] on the lowtemperature optical conductivity tie this to a large residual normal density, at odds with expectations from BCS theory and general arguments due to Legget [J. Stat. Phys 93, 927 (1998)]. We revisit these arguments in the context of superfluid hydrodynamics and demonstrate that consistently coupling the system to external sources allows for a large lowtemperature normal density. As a proofofprinciple, we use gaugegravity duality to construct an example of a stronglycoupled superfluid which has nonvanishing zerotemperature normal and superfluid densities. We find that the coexistence of the two densities at zerotemperature is a consequence of the underlying quantum critical ground state and the spectrum of irrelevant deformations around this state. Our results are in qualitative agreement with the optical conductivity as well as other previous measurements on overdoped LSCO, including the specific heat. 
Wednesday, March 17, 2021 12:30PM  12:42PM Live 
M47.00006: Enhanced A1g Raman response in unconventional superconductors due to Higgs oscillations Matteo Puviani, Dirk Manske The Higgs in superconductors is a collective amplitude mode which can couple to light only in a nonlinear Ramanlike process. Despite being so far elusive in most experiments because of physical and technical reasons, in dwave superconductors the excitation of the Higgs mode can become detectable in polarization dependent experiments. In our work, we have calculated the Raman contribution of the amplitude mode from a new perspective, including manybody dressing effects, demonstrating its role in the longstanding problem concerning the intensity of the A1g Raman spectrum in cuprates. Moreover, we apply our scheme to predict the presence of measurable characteristic oscillations in THz quenchoptical probe timedependent reflectivity experiments. 
Wednesday, March 17, 2021 12:42PM  12:54PM Live 
M47.00007: Optical responses of Higgs and Leggett modes in multiband superconductors Takumi Kamatani, Naoto Tsuji, Sota Kitamura, Takahiro Morimoto Collective excitations in superconductors are attracting much attention recently. One typical example is the Higgs mode, which is an amplitude mode of superconducting gap function. Higgs modes in superconductors are experimentally observed by Raman spectroscopy and optical measurements of third harmonic generation [1]. In multiband superconductors, the gap function contains multiple band degrees of freedom and becomes a matrix generally. Consequently, there appears another collective mode that corresponds to the oscillation of the relative phase between different bands, which is called Leggett modes. So far, Leggett modes are observed in Raman experiments using MgB2[2], while there is no optical measurement of Leggett modes. 
Wednesday, March 17, 2021 12:54PM  1:06PM Live 
M47.00008: Superconductivity in the doped quantum spin liquid on the triangular lattice HongChen Jiang Broad interest in quantum spin liquid (QSL) phases was triggered by the notion that they can be viewed as insulating phases with preexisting electronpairs, such that upon light doping they might automatically yield high temperature superconductivity. Yet despite intense efforts, definitive evidence showing that doping QSLs leads to superconductivity has been lacking. We address the problem of a lightly doped QSL through a largescale densitymatrix renormalization group study of the tJ model on the triangular lattice with a small but nonzero concentration of doped holes. We provide direct evidences that doping QSL can naturally give rise to superconductivity. The ground state is consistent with a LutherEmery liquid with powerlaw superconducting and chargedensitywave correlations but shortrange spinspin correlations. Specifically, the superconducting correlations are the dominant correlations on both fourleg and sixleg cylinders, indicating that longrange superconductivity would emerge in doping QSL in two dimensions. 
Wednesday, March 17, 2021 1:06PM  1:18PM Live 
M47.00009: Topological superconductivity in the doped chiral spin liquid on the triangular lattice YiFan Jiang, HongChen Jiang It has long been proposed that doping a chiral spin liquid (CSL) or fractional quantum Hall state can give rise to topological superconductivity. Despite of intensive effort, definitive evidences still remain lacking. We address this problem by studying the tJ model supplemented by timereversal symmetry breaking chiral interaction J_{χ} on the triangular lattice using densitymatrix renormalization group with a finite concentration δ of doped holes. It has been established that the undoped, i.e., δ=0, system has a CSL ground state in the parameter region 0.32< J_{χ}/J < 0.56. Upon light doping, we find that the ground state of the system is consistent with a LutherEmery liquid with powerlaw superconducting and chargedensitywave correlations but shortrange spinspin correlations. In particular, the superconducting correlations, whose pairing symmetry is consistent with d±idwave, are dominant at all hole doping concentrations. Our results provide direct evidences that doping the CSL on the triangular lattice can naturally give rise to topological superconductivity. 
Wednesday, March 17, 2021 1:18PM  1:30PM Live 
M47.00010: Multiorbital superconducting mechanism for a newtype cuprate Ba_{2}CuO_{3+}_{δ} based on a Lieblattice model Kimihiro Yamazaki, Masayuki Ochi, Daisuke Ogura, Kazuhiko Kuroki, Hiroshi Eisaki, Shinichi Uchida, Hideo Aoki For the newly discovered cuprate superconductor Ba_{2}CuO_{3+δ}, we propose a lattice structure which resembles the model considered by Lieb to represent the vastly oxygendeficient CuO_{2} planes [1]. We first show that the Lieblattice structure is nearly as stable as the chaintype structure known to exist as e.g. Sr_{2}CuO_{3}. Then we construct a multiorbital Hubbard model based on firstprinciples calculation, and apply the fluctuationexchange approximation. We show that swave and dwave pairings closely compete with each other and, more interestingly, that a coexistence of intra and interorbital pairings arises. We also reveal an intriguing relation of the Lieb model with the twoorbital model for the usual K_{2}NiF_{4}type cuprate where a close competition between s and dwave pairings is known to occur. We further show that s±wave superconductivity is strongly enhanced when the d_{3z2−r2} band is raised in energy so that it becomes nearly “incipient” with the lower edge of the band close to the Fermi level within a realistic band filling regime. The enhanced superconductivity in the present model is in fact shown to be related to an enhancement found previously in the bilayer Hubbard model with an incipient band. 
Wednesday, March 17, 2021 1:30PM  1:42PM Live 
M47.00011: Photoinduced ηpairing at finite temperatures Satoshi Ejima, Tatsuya Kaneko, Florian Lange, Seiji Yunoki, Holger Fehske We numerically prove photoinduced ηpairing in a halffilled fermionic Hubbard chain at both zero and finite temperature. The result, obtained by combining the matrixproductstatebased infinite timeevolving block decimation technique and the purification method, applies to the thermodynamic limit. Exciting the Mott insulator by a laser electric field docked on via the Peierls phase, we track the time evolution of the correlated manybody system and determine the optimal parameter set for which the nonlocal part of the ηpaircorrelation function becomes dominant during the laser pump at zero and low temperatures. These correlations vanish at higher temperatures and long times after pulse irradiation. In the high laser frequency strong Coulomb coupling regime we observe a remnant enhancement of the Brillouinzone boundary paircorrelation function also at high temperatures, if the Hubbard interaction is about a multiple of the laser frequency, which can be attributed to an enhanced double occupancy in the virtual Floquet state. 
Wednesday, March 17, 2021 1:42PM  1:54PM Live 
M47.00012: Quatonic and SpinQuatonic Superconductors: Twisted Bilayer Graphene and Cuprates SangBoo Nam A novel superconducting transition temperature T_{c}=nV_{BCS}/4 and energy gap Δ(T)=2T_{c}tanh[Δ(T)/2T] are presented, based on BCS framework [the cutoff energy T_{d }≤2T_{c}], where n is the carrier filling number in the primitive unit cell. The virtual exchange of Quaton (QT) [SpinQuaton (SQ)], (4 charges [spins] of 2 electrons and 2 holes on tetrahedron corners), induced by exciton [magnon], between the carriers involved, yields V_{BCS} = 2E_{QT}[E_{SQ}] (eigenenergy of QT [SQ]). For twisted bilayer graphene (TBG), E_{QT}=2E_{x }(exciton energy), E_{x} is μ, the chemical potential energy, defined by the carrier density for n=½, and T_{c}=μ/2. Using μ=0.3meV calculated by Wu et al., Phys. Rev. Lett. 121, 257001 (2018), T_{c}(TBG)=1.74K in excellent agreement with 1.7K observed by Cao et al., Nature 556, 43 (2018). For cuprates, assigning the modes at 47meV (TlBCO) and 41 – 34meV (YBCO) in the neutron and Raman scatterings, as the respective SQs, for n=1/2, T_{c }(TlBCO)=135K and T_{c }(YBCO)=119 – 98K are in agreement with the experiments. The carrier specific heat jump [C_{s}/C_{n} 1] at T_{c} is found to be 1.823 (BCS value 1.43). The result of T_{c}=N(0)T_{d}V_{BCS}/2 [Nam, Phys. Lett. A193, 111 (1994), ibid(E) A197, 458 (1995)] is recovered with n=2N(0)T_{d}, where N(0) is the density of states/spin at the reference energy. 
Wednesday, March 17, 2021 1:54PM  2:06PM Live 
M47.00013: Fluctuating PairDensity Wave in anisotropic strongly coupled pairing system Laura Fanfarillo, Chandan Setty, Peter Hirschfeld In weakly coupled BCS superconductors, only electrons within a tiny energy window around the Fermi energy form Cooper pairs. This may not be the case in strong coupling superconductors such as FeSe, SrTiO3 or cold atom condensates where the pairing scale becomes comparable or even larger than the Fermi energy. In this talk I will discuss an analytically solvable model to examine possible pairing phases in the strongly coupled regime in the presence of anisotropic interactions. I will illustrate the properties of a novel finite temperature phase where local pair correlations have nonzero centerofmass momentum but lack longrange order. Below a critical temperature such a fluctuating pairdensity wave phase can condense either to a uniform dwave superconductor or to a pairdensity wave phase depending on the strength of the pairing interaction. I will conclude discussing possible realizations of our mechanism, including cuprates, where the pseudogap phase has been postulated to be a form of incoherent pair density wave. 
Wednesday, March 17, 2021 2:06PM  2:18PM Live 
M47.00014: Finding T_{c} in an attractiveU Hubbardmetallic bilayer system. Philip Dee, Steven S. Johnston, Thomas Maier An intriguing route to higher temperature superconductivity is via coupling layers of different material properties. From a model standpoint, others have shown coupling layers with a large pairing scale, and weak superfluid stiffness to a metal can recover part of the meanfield transition temperature when coupled to a thin metallic film. But how general is this result? We examine this question by studying a bilayer system comprised of an attractive Hubbard layer and a metallic layer coupled with an interlayer hopping using the dynamical cluster approximation. Focusing on the regime where the interaction magnitude is comparable to the electronic bandwidth, we find that coupling between the layers suppresses T_{c} and that the transition evolves from a KosterlitzThouless type to a logarithmic BCS (meanfield) type transition. We will discuss the reasons for this suppression and potential future directions. 
Wednesday, March 17, 2021 2:18PM  2:30PM Not Participating 
M47.00015: Large scale simulations of topological defects in pair density waves YiHsuan Liu, TingKuo Lee, Giawei Chern Pair density wave (PDW) has been in the central stage of highTc cuprate since its direct experimental observation. A PDW is a unique superconducting state in which the electron pairing function varies periodically as a function of position. Experimentally, densitywave states of cuprates have been shown to be highly inhomogeneous, indicating the importance of both quenched disorder and topological defects. To investigate the effects of spatial inhomogeneity, we combine the kernel polynomial method (KPM), which offers linearscaling electronic structure calculation, with the renormalized meanfield theory (RMFT) for $t$$J$ model. This allows us to perform unprecedented largescale simulations, with number of lattice sites up to $N\sim 10^5$, of PDW states. In particular, we are trying to investigate the solutions with fractionalized halfvortices with a dislocation of the charge stripes. We also compute the local electronic density of states of these novel inhomogeneous PDW states. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2021 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700