Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session K25: Superconductivity: Theory I 
Hide Abstracts 
Sponsoring Units: DCMP Chair: Harald Jeschke, GoetheUniversität Frankfurt Room: 324 
Wednesday, March 16, 2016 8:00AM  8:12AM 
K25.00001: Revised phase diagram and anomalous thermal evolution of the antinodal gap and Raman response in hightemperature superconductors Yuan Zhou, Zuodong Yu, Weiguo Yin, Haiqing Lin, Changde Gong The interplay of competing orders is essential to hightemperature superconductivity, which emerges upon suppression of an antiferromagnetic order typically via charge doping. However, where the zerotemperature quantum critical point (QCP) takes place  in terms of the doping level  is still elusive for it is hidden by the superconducting dome. The QCP has long been believed to follow the continuous extrapolation of the characteristic temperature (T*) for a normalstate order, but recently T* within the superconducting dome was found to exhibit unexpected backbending in the cuprate Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ and the ironpnictide BaFe$_{1x}$Co$_{x}$As. Here we show that the original and the revised phase diagrams can be understood in terms of weak and moderate competitions, respectively, between superconductivity and a pseudogap state such as ddensitywave, based on GinzburgLandau theory and the microscopic extended tJ model. We further illustrate that the anomalous thermal dependences of the measured antinodal gap and Raman response in cuprates can be well understood by a twostep evolution, dominated by superconductivity and pseudogap, respectively. [Preview Abstract] 
Wednesday, March 16, 2016 8:12AM  8:24AM 
K25.00002: The Andreev reflection in a superconductornormal metal junction of a doped correlated quantum spin Hall insulator YungYeh Chang, ChungYu Mou, ChungHou Chung Andreev conductance across a normal metalsuperconductor (NS) junction of doped correlated quantum spin Hall insulator on honeycomb lattice is theoretically studied via BlonderTinkhamKlapwijk (BTK) formalism. The normal side is modeled by the doped KaneMele (KM) model. The superconducting side is a doped correlated KM tJ model, which has been shown to feature d+id'wave spin singlet pairing. With increasing intrinsic spinorbit coupling, the doped KM tJ system undergoes a topological phase transition from the chiral dwave superconductivity to the $Z_{2}$ spinChern superconducting phase with helical Majorana fermions at edges. We apply a local strain on the NS interface to generate an effective Diracdelta barrier and study the transport near the chiralhelical phase transition in the weak tunneling limit. We explore the Andreev conductance at the K and K’ Dirac points, respectively and find the distinctive behaviors across the transition. Relevance of our results for the adatomdoped graphene is discussed. Reference: S.J. Sun, C.H. Chung, Y.Y. Chang, W.F. Tsai, and F.C. Zhang, arxiv:1506.02584." [Preview Abstract] 
Wednesday, March 16, 2016 8:24AM  8:36AM 
K25.00003: Macroscopic character of composite high temperature superconducting wires Steven Kivelson, Boris Spivak The ``dwave'' symmetry of the superconducting order in the cuprate high temperature superconductors is a well established fact, and one which identifies them as ``unconventional.'' However, in macroscopic contexts  including many potential applications ({\it i.e.} superconducting ``wires'')  the material is a composite of randomly oriented superconducting grains in a metallic matrix, in which Josephson coupling between grains mediates the onset of longrange phase coherence. Here, we analyze the physics at length scales large compared to the size of such grains, and in particular the macroscopic character of the longrange order that emerges. While XYsuperconducting glass order and macroscopic dwave superconductivity may be possible, we show that under many circumstances  especially when the dwave superconducting grains are embedded in a metallic matrix  the most likely order has global swave symmetry. [Preview Abstract] 
Wednesday, March 16, 2016 8:36AM  8:48AM 
K25.00004: Random field disorder and charge order driven quantum oscillations in cuprates Antonio Russo, Sudip Chakravarty In the pseudogap regime of the cuprates, charge order breaks a $\mathbb{Z}_{2}$ symmetry. Therefore, the interaction of charge order and quenched disorder due to potential scattering, can, in principle, be treated as a random field Ising model. A numerical analysis of the ground state of such a random field Ising model reveals local, glassy dynamics in both $2D$ and $3D$. The glassy dynamics are treated as a heat bath which couple to the itinerant electrons, leading to an unusual electronic nonFermi liquid. If the dynamics are strong enough, the electron spectral function has no quasiparticle peak and the effective mass diverges at the Fermi surface, precluding quantum oscillations. In contrast to charge density, $d$density wave order (reflecting staggered circulating currents) does not directly couple to potential disorder, allowing it to support quantum oscillations. At fourth order in Landau theory, there is a term consisting of the square of the $d$density wave order parameter, and the square of the charge order. This coupling could induce parasitic charge order, which may be weak enough for the Fermi liquid behavior to remain uncorrupted. Here, we argue that this distinction must be made clear, as one interprets quantum oscillations in cuprates. [Preview Abstract] 
Wednesday, March 16, 2016 8:48AM  9:00AM 
K25.00005: Onsager rule, quantum oscillation frequencies, and the density of states in the mixedvortex state of cuprates Zhiqiang Wang, Sudip Chakravarty Onsager rule that determines the frequencies of quantum oscillations in high magnetic fields serves as an anchor point. In its absence it would be very difficult to interpret the experimental results, because for each instance the problem would have to be considered anew. In the mixedvortex state of the underdoped cuprates where, major consequential discoveries have recently taken place, its validity has been recently questioned. Here we show that this rule remains intact to an excellent approximation. The models we consider are fairly general, consisting of a variety of density wave states combined with $d$wave superconductivity. Another exceptionally interesting result from our model calculations is that the oscillations ride on top of a field independent density of states, $\rho(B)$, for higher fields. This feature appears to be consistent with the recent specific heat measurements. [Preview Abstract] 
Wednesday, March 16, 2016 9:00AM  9:12AM 
K25.00006: Collective modes in nonuniform superconductors Anton Vorontsov, Andrew Hammer We study dynamics of a superconducting condensate in the presence of a domain wall defect in the order parameter. We find that broken translation and reflection symmetries result in new collective excitations, bound to the domain wall region. Two additional amplitude/Higgs modes lie below the bulk pairbreaking edge $2\Delta$; one of them is a Goldstone mode with vanishing excitation energy. Spectrum of bound collective modes is related to the topological structure and stability of the domain wall. The `unbound' bulk collective modes and transverse gauge field mostly propagate across the domain wall, but the longitudinal component of the gauge field is completely reflected. Softening of the amplitude mode suggests reduced damping and possible route to its detection in geometrically confined superfluids or in superconductorferromagnetic heterostructures. [Preview Abstract] 
Wednesday, March 16, 2016 9:12AM  9:24AM 
K25.00007: Quasiclassical approach to magnetic suceptibility Caroline Richard, Anton Votontsov Quasiclassical theory is a powerful technique that allows calculation of physical observables using just the lowenergy states of the system. It is especially useful in studying properties of the nonuniform superfluid phases. We extend this approach to calculate response functions that involve highenergy correlations. Using example of Pauli magnetic susceptibility we employ Andreev approximation to express the spinspin correlation function near a pairbreaking surface, in terms of lowenergy, highenergy and mixed state contributions. This provides a convenient way to calculate response of a nonuniform superconductor at finite $q$vectors. [Preview Abstract] 
Wednesday, March 16, 2016 9:24AM  9:36AM 
K25.00008: Boosted one dimensional superconductors on a lattice Sayonee Ray, Subroto Mukerjee, Vijay B. Shenoy We study the effect of a boost (that engenders a currentcarrying state) on one dimensional systems of lattice fermions with shortranged attractive interactions. In the absence of a boost such systems possess algebraic superconducting order. Naively, one might expect a boost to weaken and ultimately destroy superconductivity, as in higher dimensions. However, we show that for one dimensional systems its effect is to {\em strengthen} the algebraic superconducting order by making correlation functions fall off more slowly with distance. We explain the physical underpinnings of these findings. [Preview Abstract] 
Wednesday, March 16, 2016 9:36AM  9:48AM 
K25.00009: ABSTRACT WITHDRAWN 
Wednesday, March 16, 2016 9:48AM  10:00AM 
K25.00010: The superconducting state of Holstein model using dynamical mean field theory Chungwei Lin, Bingnan Wang, Koon Teo To enhance the superconducting temperature within the conventional superconductors, we solve the Holstein model, where conduction electrons are coupled to some boson field, using dynamical mean field theory (DMFT) with the configuration interaction impurity solver. Thanks to the nonperturbative nature of DMFT, we determine the zerotemperature order parameter for a wide range of boson energies to find the optimal range for superconductivity. This is beyond the MigdalEliashberg theory where the boson energy is assumed to be small compared to the Fermi energy. The effect of Hubbard onsite repulsion will be also discussed. [Preview Abstract] 
(Author Not Attending)

K25.00011: Unconventional superconductivity and interaction induced Fermi surface reconstruction in the twodimensional Edwards model DaiNing Cho, Steffen Sykora We study the possibility of unconventional superconducting pairing in the framework of a novel twodimensional quantum transport model, where the charge carriers are strongly affected by the correlations and fluctuations of a background medium, described by bosonic degrees of freedom. Using the projective renormalization method (PRM) we find in the halffilled band case an interplay between stable superconducting solutions and a chargedensity wave order parameter which determines the ground state in the limit of large bosonic energies. The superconducting pairing mainly appears on a new holelike Fermi surface, which is formed nearby the center of the Brillouin zone due to strong renormalization of the original fermionic band. In the superconducting state, the Fermi surface splits into two disconnected parts, which are characterized by different sign of the superconducting order parameter. [Preview Abstract] 
Wednesday, March 16, 2016 10:12AM  10:24AM 
K25.00012: A comprehensive model for high$T_c$ based on pairpair interactions. William Sacks, Alain Mauger, Yves Noat The superconducting (SC) state of cuprates is characterized by a domeshaped $T_c$ versus carrier density and an unconventional {\it pseudogap} (PG) state above $T_c$  basic properties remain highly debated. We have recently proposed a mechanism [1] based on the mutual interaction between incoherent Cooper pairs existing above $T_c$. At the critical temperature, this interaction induces a Boselike condensation leading to the coherent SC state. \\ Absent in the conventional BCS case, the mutual pairpair interaction is proportional to the condensate density $n_{oc}(T)$ but is also related to the quasiparticle excitations. It gives an excellent fit to the DOS as measured by electron tunneling for a wide range of samples and carrier concentration. We conclude that longrange order is achieved by a direct quasiparticle  Cooperpair coupling. \\ We then focus on the {\it temperature dependence} of the thermodynamic functions (condensation energy, entropy, etc.) and of the quasiparticle DOS. We show that these quantities depend on the unique combination of pair (boson) and quasiparticle (fermion) excitations, allowing a qualitative understanding of the phase diagram.\\ [1] W. Sacks, A. Mauger, Y. Noat, Superconduct. Sci.Technol. {\bf 28} 105014, 2015 [Preview Abstract] 
Wednesday, March 16, 2016 10:24AM  10:36AM 
K25.00013: Two types of superconducting domes in unconventional superconductors Tanmoy Das, Christos Panagopoulos In this talk, we present a comprehensive analysis of the SC properties and phase diagrams across several families of unconventional superconductors within the copperoxides, heavyfermions, organics, and the recently discovered ironpnictides, ironchalcogenides, and oxybismuthides. We find that there are two types of SC domes present in all families of SC materials, arising sometimes as completely isolated, or merged into one, or in some materials only any one of them appears. One of the SC dome appearing at or near a possible QCP usually possesses a lower transition temperature ($T_{\mathrm{c}})$. The other SC dome appearing at a different value of the tuning parameter around a nonFermi liquid (NFL) state often has higher $T_{\mathrm{c}}$. Both SC domes are not necessarily linked to each other, and so does the QCP and NFL state. In materials, where both domes are present, they can be isolated by multiple tuning (such as such as disorder, or pressure, or magnetic field in addition to doping, and vice versa), giving a unique opportunity to decouple the relationship between QCP, NFL, and their role on superconductivity. The systematic study the NFL state might be a generic route to higher$T_{\mathrm{c}}$ superconductivity. [Preview Abstract] 
Wednesday, March 16, 2016 10:36AM  10:48AM 
K25.00014: Theory of pumpprobe photoemission from a dwave superconductor Benjamin Nosarzewski, Brian Moritz, Alexander F. Kemper, James K. Freericks, Thomas P. Devereaux Motivated by recent trARPES experiments on hightemperature superconductors, we use the nonequilibrium Keldysh formalism to study the timeresolved photoemission spectra of a model electronboson coupled system out of equilibrium. We introduce a momentum dependence to the electronboson coupling to produce a superconducting state with dwave symmetry. We investigate the nature of quasiparticle relaxation and recombination as well as the signatures of amplitude mode oscillations of the superconducting order parameter. We interpret our results in terms of existing experiments in the cuprates. [Preview Abstract] 
Wednesday, March 16, 2016 10:48AM  11:00AM 
K25.00015: First principles calculations of La$_2$CuO$_4$ Andrei Plamada, Anton Kozhevnikov, Urs Haehner, Mi Jiang, Peter Staar, Thomas Maier, Thomas Schulthess We use the DFT+DCA method for a highend study of the electronic structure properties of La$_2$CuO$_4$. The parameters of a tightbinding model are created using the firstprinciples electronic structure calculations. The allelectron fullpotential linearised augmented planewave method is used to solve the noninteracting band problem. Then the set of physically relevant Wannier functions is chosen as a basis for the underlying Hubbard model. The Wannier functions and the corresponding noninteracting Hamiltonian $H_{nm}^{0}({\bf k})$ are created using the wellestablished downfolding approach. The screened Coulomb interaction parameters $U_{nm}$ of the model are computed using the constrained randomphase approximation technique. The double counting term is assumed to be a constant multiplied by the identity operator in the correlated subspace and it is determined based on firstprinciples considerations. The resulting {\it abinitio} parameterisation of the Hubbard model is solved within dynamical cluster approximation (DCA). [Preview Abstract] 
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. 
© 2024 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700