Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session D52: Optical Probes in Copper-oxide Superconductors |
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Sponsoring Units: DCMP Chair: Nan-Lin Wang, Chinese Academy of Sciences Room: Mile High Ballroom 1F |
Monday, March 3, 2014 2:30PM - 2:42PM |
D52.00001: Optical conductivity of nodal metals C.C. Homes, G.D. Gu, J.J. Tu, J. Li, A. Akrap Fermi liquid theory is remarkably successful in describing the transport and optical properties of metals; at frequencies higher than the scattering rate, the optical conductivity adopts the well-known power law behavior $\sigma_1(\omega) \propto \omega^{-2}$. We have observed an unusual non-Fermi liquid response $\sigma_1(\omega) \propto \omega^{-1\pm 0.2}$ in the ground states of several quasi two-dimensional cuprate (optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, optimally and underdoped YBa$_2$Cu$_3$O$_{7-\delta}$) and iron-based materials ($A$Fe$_2$As$_2$, $A=$Ba, Ca) which undergo electronic or magnetic phase transitions resulting in dramatically reduced or nodal Fermi surfaces. The identification of an inverse (or fractional) power-law behavior in the residual optical conductivity now permits the removal of this contribution, revealing the direct transitions across the gap and allowing the nature of the electron-boson coupling to be probed. The non-Fermi liquid behavior in these systems may be the result of a common Fermi surface topology of Dirac cone-like features in the electronic dispersion. [Preview Abstract] |
Monday, March 3, 2014 2:42PM - 2:54PM |
D52.00002: Optical Birefringence and Dichroism of Cuprate Superconductors in the THz regime Y. Lubashevsky, LiDong Pan, T. Kirzhner, G. Koren, N.P. Armitage The presence of optical polarization anisotropies, such as Faraday/Kerr effects, linear birefringence, and magnetoelectric birefringence are evidence for broken symmetry states of matter. The recent discovery of a Kerr effect using near-IR light in the pseudogap phase of the cuprates can be regarded as a strong evidence for a spontaneous symmetry breaking and the existence of an anomalous long-range ordered state. In this work we present a high precision study of the polarimetry properties of the cuprates in the THz regime. While no Faraday effect was found in this frequency range to the limits of our experimental uncertainty (1.3 milli-radian or 0.07$^\circ$), a small but significant polarization rotation was detected that derives from an anomalous linear dichroism. In YBa$_2$Cu$_3$O$_y$ the effect has a temperature onset that mirrors the pseudogap temperature T$^*$ and is enhanced in magnitude in underdoped samples. In $x=1/8$ La$_{2-x}$Ba$_{x}$CuO$_4$, the effect onsets above room temperature, but shows a dramatic enhancement near a temperature scale known to be associated with spin and charge ordered states. These features are consistent with a loss of both C$_4$ rotation and mirror symmetry in the electronic structure of the CuO$_2$ planes in the pseudogap state. [Preview Abstract] |
Monday, March 3, 2014 2:54PM - 3:06PM |
D52.00003: Quasiparticle dynamics in YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ films probed by broadband pump-probe spectroscopy Chunfeng Zhang, Wei Li, Benjamin Gray, Xiaoyong Wang, Jak Tchakhalian, Min Xiao Ultrafast pump-probe spectroscopy can provide viable information on quasiparticle dynamics with respect to phase transition and competing orders in high temperature superconductors. We study the quasiparticle dynamics in epitaxial YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ films by probing photo-induced reflectivity change over a broadband spectral coverage. The dynamic traces probed at single wavelength show abrupt changes of signal amplitude and decay lifetime at the superconducting transition temperature. The spectra dispersion of reflectivity change at zero temporal delay induced by electronic excitation is found to be quite different in superconducting and normal phases. Moreover, the spectral dispersion is strongly dependent on the delay time between the pump and probe pulse, implying evolution of spectral weight transition contributed by electronic and photonic process. These results are helpful to understand the electronic excitations and their interaction with different bosonic modes in cuprates. [Preview Abstract] |
Monday, March 3, 2014 3:06PM - 3:18PM |
D52.00004: Near-field techniques for probing collective modes of anisotropic superconducting thin films H.T. Stinson, J.S. Wu, B.Y. Jiang, Z. Fei, A.S. Rodin, B. Chapler, A.S. Mcleod, A. Castro-Neto, Y.S. Lee, M.M. Fogler, D.N. Basov We propose the use of scattering-type scanning near-field optical microscopy (s-SNOM) to characterize the collective mode spectrum of anisotropic superconductors. To probe the dispersion of collective modes with large in-plane momenta, specifically surface plasmons and guided wave modes, we model the real-space interference patterns of modes launched by the sharp s-SNOM tip and their reflections off physical and electronic boundaries. In addition, we show that s-SNOM spectroscopy allows for a direct probe of the $c$-axis superfluid density in underdoped anisotropic superconductors with nanoscale spatial resolution. [Preview Abstract] |
Monday, March 3, 2014 3:18PM - 3:30PM |
D52.00005: Quasiparticle recombination dynamics in the model cuprate superconductor HgBa$_{2}$CuO$_{4+\delta}$ J.P. Hinton, E. Thewalt, J.D. Koralek, J. Orenstein, N. Barisic, X. Xhao, M. Chan, C. Dorow, M. Veit, L. Ji, M. Greven The cuprate family of high temperature superconductors is characterized by a variety of electronic phases which emerge when charge carriers are added to the antiferromagnetic parent compound. The structural simplicity of the single layer cuprate system HgBa$_{2}$CuO$_{4+\delta}$ (Hg1201) is advantageous for experimentally detecting subtle features of these phases. In this work, we investigate the recombination dynamics of photo-excited quasiparticles in Hg1201 as a function of doping, temperature, and magnetic field using pump-probe optical reflectivity. We observe two distinct onset temperatures above T$_{C}$ in the underdoped part of the phase diagram, corresponding to T* and T** as observed in transport and neutron scattering experiments. We also measure a suppression of the recombination rate near TC which peaks at 8\% hole concentration. We associate this suppression with coherence effects. Lastly, we observe a complex, non-monotonic temperature dependence in the dynamics around optimal doping, providing evidence for reentrant phase transitions near the apex of the superconducting dome. [Preview Abstract] |
Monday, March 3, 2014 3:30PM - 3:42PM |
D52.00006: Infrared Faraday Measurements on Cuprate High Temperature Superconductors M. Murat Arik, Alok Mukherjee, John Cerne, Y. Lubashevsky, LiDong pan, N.P. Armitage, T. Kirzhner, G. Koren Recent measurements on cuprate high temperature superconductors (CHTS) have observed evidence for symmetry breakings in the pseudogap phase, suggesting that this is a full-fledged phase with an actual broken symmetry. To test the spectral character of this broken symmetry, we have made infrared polarization-sensitive measurements in the absence of magnetic field on a series of CHTS films. We have studied the Faraday effect (change in the polarization of transmitted light) in CHTS films as a function of temperature (10-300K), energy (0.1-3 eV), and sample orientation with respect to the incident light polarization. We observe a strong linear optical anisotropy, well above the superconducting transition temperature. This signal is maximized when the sample lattice axes are oriented near 45o with respect to the incident light polarization, and varies as the sample is rotated. We explore the temperature and energy dependence of this signal. [Preview Abstract] |
Monday, March 3, 2014 3:42PM - 3:54PM |
D52.00007: The evolution of microwave conductivity in YBa$_2$Cu$_3$O$_{6+x}$ across the superconducting dome Jordan Baglo, James Day, Pinder Dosanjh, Ruixing Liang, Walter Hardy, Doug Bonn The rich phenomenology displayed in the phase diagram of the high-$T_c$ cuprates continues to be an active arena of investigation. Recent experimental and theoretical work appears to be converging on a picture of separate spin and charge order phase transitions -- well-below and near optimal doping, respectively -- along with associated Fermi surface reconstruction. As sensitive probes of the low-energy electrodynamics, microwave spectroscopy techniques are well-suited for characterizing the effects of such changes in electronic structure deep within the superconducting state. I will present the results of our survey of the complex microwave conductivity of YBa$_2$Cu$_3$O$_{6+x}$ over a wide range of oxygen contents, from 6.49 to 6.998, and discuss their implications for the evolution of electronic structure with doping. I will also discuss the surprising relationship we observed between quasiparticle scattering lifetimes and oxygen ordering, which carries important implications for quantum oscillation measurements. [Preview Abstract] |
Monday, March 3, 2014 3:54PM - 4:06PM |
D52.00008: Magnetic and Chiral Excitations in Resonant Raman Scattering Thomas Devereaux, Chunjing Jia, Yao Wang, Brian Moritz, Rudi Hackl For the strongly correlated materials such as the cuprate parent compounds, the two-magnon excitations can be measured by the Raman scattering imposing the B1g symmetry, while chiral excitations can be probed using circularly polarized light. We study the resonance enhancement of these excitations and their relationship to the optical conductivity based on cluster exact diagonalization studies of the single-band as well as multi-orbital Hubbard models. Our theoretical studies help understand Raman experiments for the half-filled cuprates as well as the lightly doped (electron and hole doped) cuprates, and the relationships to other experiments on the same materials. [Preview Abstract] |
Monday, March 3, 2014 4:06PM - 4:18PM |
D52.00009: Ultrafast dynamics in photo-induced correlated electronic states in ladder cuprates Sumio Ishihara, Hiroshi Hashimoto Ultrafast photo-induced dynamics in correlated electron systems, in particular, photon irradiation effects in half filled Mott insulators have been studied intensively from theoretical and experimental sides, and photo-induced Mott insulator to metal transition has been observed. On the other side, in recent ultrafast pump-probe experiments in ladder cuprates away from half filling, photo-irradiation weakens initial metallic state. We study ultrafast dynamics in photo-induced states in a ladder system. Real time dynamics in a ladder-type Hubbard model are analyzed by the numerical exact diagonalization method. Optical conductivity spectra and density of states show that the initial metallic state is changed into a bad metallic state by photo irradiation, in contrast to the photo-doped effect in half-filled Mott insulators. Through the calculation of the carrier pair correlation functions, we find that coherent motion of carrier pairs in initial states are reduced by pump photon irradiation. We further simulate a double pulse irradiation. Our simulations as well as the experimental results suggest an optical control of pair coherence in correlated electron system. [Preview Abstract] |
Monday, March 3, 2014 4:18PM - 4:30PM |
D52.00010: Frequency dispersion of nonlinear response of thin superconducting films Sean Byrnes, Scott Dietrich, Sergey Vitkalov, Andrey Sergeev Effect of microwave radiation on transport properties of $La_{2-x}Sr_xCuO_4$ atomically thin films grown by Molecular Beam Epitaxy were studied. Resistance changes induced by the applied microwaves with variable frequencies (0.1-20GHz) and powers were measured at different temperatures near the superconducting transition ($\sim 8-15$K). Strong drop of three orders of magnitude of the nonlinear response is found within a few GHz of a cutoff frequency ($\omega_{cut}\sim 2GHz$). Expected frequency dependence vastly underestimates the sharpness of this drop. Numerical simulations considering an $ac$ response which follow the $dc$ I-V characteristics of the films replicate the low frequency behavior, but fail above the threshold frequency $\omega_{cut}$. The observed phenomenon suggests significant decrease of the effectiveness of vortex-antivortex dissociation induced by the oscillating superconducting condensate. [Preview Abstract] |
Monday, March 3, 2014 4:30PM - 4:42PM |
D52.00011: Charge-orbital-lattice coupling in a quasi-one-dimensional cuprate revealed through energy shifts in the dd-excitation profile B. Moritz, J.J. Lee, W.-S. Lee, M. Yi, C.J. Jia, A.P. Sorini, K. Kudo, Y. Koike, K.J. Zhou, C. Monney, V. Strocov, L. Patthey, T. Schmitt, Z.-X. Shen, T.P. Devereaux One-dimensional edge-sharing copper oxides provide a unique opportunity to study the effects of electron-lattice (e-l) interactions without complication from magnetic degrees of freedom which have a much lower energy scale in these compounds. Building on the characterization of e-l coupling in these materials from the elastic line profile found in resonant inelastic x-ray scattering (RIXS) at the O K-edge, new analysis of dd-excitation peak positions in Cu L-edge RIXS reveals abrupt shifts as one tunes the incident photon energy through the resonance. The observations point toward an orbital-specific coupling of the high-energy excited states of the system to the low-energy degrees of freedom. A Franck-Condon treatment of e-l coupling, consistent with other measurements, reproduces these shifts and highlights charge-orbital-lattice renormalization in the high energy d-manifold with obvious repercussions for other copper oxides. [Preview Abstract] |
Monday, March 3, 2014 4:42PM - 4:54PM |
D52.00012: Dynamical Mass Renormalization and Fermi Momentum in the Normal State of the Cuprate $Bi_{2} Sr_{2} CaCu_{2} O_{8+x} $ as Instigated and Observed by Two-Photon ARPES J. Rameau, S. Freutel, L. Rettig, I. Avigo, M. Ligges, Y. Yoshida, H. Eisaki, J. Schneeloch, R. Zhong, Z. Xu, G. Gu, P. Johnson, U. Bovensiepen The dressing of quasiparticles in solids is investigated by observing changes of the electronic structure $E$(\textbf{\textit{k}}) driven by femtosecond laser pulses. Employing time- and angle-resolved photoemission on the optimally doped cuprate $Bi_{2} Sr_{2} CaCu_{2} O_{8+x} $, just above $T_{c} $, we observe two effects with different characteristic temporal evolutions and, therefore, different microscopic origins. The experiment was carried out using amplified ultrafast laser pulses and a novel time of flight laser-ARPES setup. Both of the effects observed thusly are driven by the relatively high fluences of our amplified near-infrared pump laser and indicate that non-trivial, dynamical changes of the normal state cuprate band structure may be induced by ultrafast laser pulses over time scales at least as short as 150 fs. First, a 10{\%} change of the effective mass due to the 70~meV kink in $E$(\textbf{\textit{k}}) is found to occur during the experiment's 100~fs temporal resolution. Second, a time- and fluence-dependent change in $k_{F} $ is observed. The causes and ramifications of these disparate processes will be discussed. [Preview Abstract] |
Monday, March 3, 2014 4:54PM - 5:06PM |
D52.00013: Quantum quenching an O(N) non linear sigma model (NLSM) and oscillation experiments of high Tc underdoped cuprate superconductor Ling Yan Hung, Wenbo Fu, Subir Sachdev Recent X-ray scattering experiments have provided strong evidence of the coexistence of a charge density wave order (CDW) and superconductivity (SC) in underdoped crystals of the prototypical high-$T_c$ cuprate superconductor, YB$_{a_2}$Cu$_3$O$_{6+x}$. Sachdev et al have proposed a O(6) NLSM as an effective description of the competing orders, which finds excellent quantitative fit with the X-ray data. On the other hand, Hinton et al report coherent oscillations associated with CDW in these cuprates, whose phenomenology above and below T$_c$ find qualitative match with the picture of the competing orders. Motivated by these recent results, we study the dynamical evolution of the O(6) NLSM model upon a quantum quench -- a sudden disturbance of some parameters of the model to mimic the effect of the laser pulse in the oscillation experiment. As a first brush, we simplify the problem by taking the large-N limit of the O(6) NLSM. We observe a general exponentially decaying oscillations, which experiences phase shift as temperature is varied, at an extent determined by the specific choice of the parameter that is quenched. We also discuss the variation of the oscillation frequency and amplitude as various parameters are varied. [Preview Abstract] |
Monday, March 3, 2014 5:06PM - 5:18PM |
D52.00014: IR Hall Effect for reconstructed Fermi surfaces Dennis Drew The IR Hall Effect in the presence of Fermi surface reconstruction is considered within a density wave model for a 2D metal. Reconstruction of a hole like Fermi surface can produce reconstructed electron-like or hole-like Fermi surfaces. For hole-like reconstruction the inverse Hall frequency (1/$\omega_{\mathrm{H}})$ remains positive. For an electron like reconstruction 1/$\omega_{\mathrm{H}}$ remains hole-like for small density wave gaps and passes continuously through zero as the gap become larger and the electron-like pockets becomes convex. These considerations are applied to IR Hall data on under doped YBCO. It is concluded that the reconstructed Fermi surface in under doped YBCO is hole-like. [Preview Abstract] |
Monday, March 3, 2014 5:18PM - 5:30PM |
D52.00015: Nonadiabatic dynamics and coherent control of nonequilibrium superconductors Andreas Schnyder Motivated by recent THz pump-THz probe experiments on NbN films [1], we theoretically study the pump-probe response of nonequilibrium superconductors coupled to optical phonons. For ultrashort pump pulses a nonadiabatic regime emerges, which is characterized by oscillations of the superconducting gap [2] and by the generation of coherent phonons [3]. Using density-matrix theory, we compute the pump-probe response of the superconductor in the nonadiabatic regime and determine the signatures of the order parameter and of the phonon oscillations in the pump-probe conductivity. We find that the nonadiabatic dynamics of the superconductor reflects itself in oscillations of the pump-probe response as a function of delay time between pump and probe pulses [4]. We argue that from the analysis of this oscillatory behavior both frequency and decay time of the algebraically decaying order-parameter oscillations can be inferred.\\[4pt] [1] R. Matsunaga \textit{et. al.}, Phys. Rev. Lett. \textbf{111}, 057002 (2013). \newline [2] E. A. Yuzbashyan \textit {et. al.}, Phys. Rev. Lett. \textbf{96}, 097005 (2006). \newline [3] A. P. Schnyder \textit {et. al.}, Phys. Rev. B \textbf{84}, 214513 (2011). \newline [4] H. Krull \textit {et. al.}, arXiv:1309.7318 (submitted). [Preview Abstract] |
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