Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session F35: HTSC: ARPES and TR-ARPES |
Hide Abstracts |
Sponsoring Units: DMP Chair: Lex Kemper, Lawrence Berkeley National Laboratory Room: 343 |
Tuesday, March 19, 2013 8:00AM - 8:12AM |
F35.00001: Determinining the Critical Condition for Superconductivity in Bi$_{2}$Sr$_{2}$CaCuO$_{8+\delta }$ T. Reber, S. Parham, Y. Cao, J. Waugh, H. Li, N. Plumb, Q. Wang, G. Gu, Y. Yoshida, Y. Aiura, H. Eisaki, G. Arnold, D. Desssau Using the tomographic density of states (TDoS) ARPES-based technique we present a detailed study of the temperature and doping dependences of the pair-forming, represented by the gap magnitude ($\Delta )$, and pair-breaking, represented by the scattering rate ($\Gamma )$, ~processes in BSCCO.~ We find that $\Delta $ is finite through the superconducting transition, T$_{C}$, and ceases only at the higher temperature T$_{Pair}$, which corresponds with the T$_{Onset}$~from Nernst experiments rather than the T* tied to the antinodal pseudogap.~ Furthermore, we find $\Gamma $ is large and strongly temperature dependent and T$_{C}$~is strongly correlated with the ratio of $\Delta $/$\Gamma $.~ Consequently, the presence of pairs is not sufficient for superconductivity: the pair-breaking processes must also be diminished to the point that pairs have a long enough lifetime to develop long range coherence.~ [Preview Abstract] |
Tuesday, March 19, 2013 8:12AM - 8:24AM |
F35.00002: The Effects of Impurities and Disorder on the ARPES lineshapes of Bi2212 Stephen Parham, Theodore Reber, Yue Cao, Justin Waugh, Haoxiang Li, Z. Xu, J. Schneeloch, R.D. Zhong, Genda Gu, Hiroshi Eisaki, Daniel Dessau We present a study of Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCuO$_{\mathrm{8}}$ doped with various magnetic impurities, Fe and Ni. Through the use of our Tomographic Density of States or TDoS technique, we show that these magnetic impurities decrease the lifetime of the Cooper pairs in this material, while leaving the superconducting gap essentially unchanged. These effects are masked using traditional MDC/EDC analyses and thus our results highlight the usefulness of the TDoS technique. Even without impurities, there is gap disorder in these materials that is readily seen in STM experiments. This gap disorder affects the TDoS lineshape, and we show that the disorder predicted from our TDoS technique is consistent with that measured through STM. [Preview Abstract] |
Tuesday, March 19, 2013 8:24AM - 8:36AM |
F35.00003: Observation of symmetry-distinct states proximate to the Fermi level in a high-Tc cuprate family Rui-Hua He, M. Hashimoto, K. Tanaka, A. Sorini, S.-K. Mo, T. Sasagawa, M. Fujita, T. Adachi, M. Enoki, S. Iikubo, N. Mannella, Hong Yao, M. Yi, W. Meevasana, Y. He, K. Yamada, Y. Koike, T. P. Devereaux, Z. Hussain, Z.-X. Shen Current understanding of cuprate superconductivity is based exclusively on an effective one-band electronic band structure formed by states of in-plane dx2-y2 symmetry. By studying the La-based cuprates with polarization-dependent angle-resolved photoemission spectroscopy, here we uncovered another group of states of distinct c-axis symmetry that coexists with the dx2-y2-symmetry states near the Fermi level and eluded previous detection. As functions of momentum and doping, these new states show overall different dispersion relations yet a qualitatively similar low-energy (pseudo)gapping behavior as the dx2-y2-symmetry states, until they become closely degenerate above $\sim$20{\%} doping. [Preview Abstract] |
Tuesday, March 19, 2013 8:36AM - 8:48AM |
F35.00004: Fine doping and temperature dependent ARPES study in deeply undersoped LSCO system Yu He, Ruihua He, Makoto Hashimoto, Sung-Kwan Mo, Seiki Komiya, Zhi-Xun Shen Deeply underdoped cuprates are known to be a host system for strong electron-phonon coupling physics. Set in the picture of lightly doped Mott insulator, extremely underdoped cuprates show prevailing evidence of polaron formation, as a natural result of strong bosonic interaction, which have gained support from both optical and transport measurements. Based on K. Shen and O. Roesch's pioneering work, we further studied fine doping and temperature dependence in the low-doping LSCO system, where antiferromagnetism and spin glass phases still persist. In this work, we will discuss the change in Fermi velocity in terms of doping, evolution of nodal gap as function of temperature and the possible contribution from lattice/spin degree of freedom in light of the small polaron's existence. Comparison with similar observations in manganites and iron-chalcogenides will be discussed to further address the ubiquity of the polaron physics in strongly correlated electron systems. [Preview Abstract] |
Tuesday, March 19, 2013 8:48AM - 9:00AM |
F35.00005: Laser-ARPES studies of dispersion kinks in cuprate phase diagram I.M. Vishik, M. Hashimoto, S. Johnston, W.-S. Lee, F. Schmitt, R.G. Moore, D.H. Lu, T. Sasagawa, S. Uchida, S. Ishida, K. Fujita, M. Ishikado, Y. Yoshida, H. Eisaki, R.-H. He, Z. Hussain, T.P. Devereaux, Z.-X. Shen Angle-resolved photoemission spectroscopy (ARPES) reveals ubiquitous dispersion kinks in cuprates which are manifestations of electron-boson coupling, potentially related to the superconductivity pairing mechanism. We report new temperature-, momentum-, and doping- dependent laser-ARPES measurements of the energy and coupling strength of the ubiquitous kink near 70 meV in Bi$_{\mathrm{2}}$Sr$_{\mathrm{2}}$CaCu$_{\mathrm{2}}$O$_{\mathrm{8+\delta }}$ (Bi-2212). The apparent kink energy below T$_{\mathrm{c}}$ is related to the mode energy modulo the maximum of the $d$-wave superconducting gap, and the pseudogap similarly needs to be considered above T$_{\mathrm{c}}$. Following improvements in data quality as well as recent comprehensive gap measurements throughout the phase diagram, we can better assess the phenomenology and origin of dispersion anomalies. [Preview Abstract] |
Tuesday, March 19, 2013 9:00AM - 9:12AM |
F35.00006: Autocorrelation of ARPES Spectra in the Pseudogap State of the Underdoped Curpates Jonathan Rameau, Hongbo Yang, Cherise Burton, Tim Kidd, Maurice Rice, Peter Johnson It has long been known that the normal state of the underdoped cuprate high $T_{c}$ superconductors is characterized by a pseudogap in the anti-nodal region of the Brillouin zone and a set of disconnected set of excitations at the chemical potential, in the nodal region, known as Fermi arcs. Recently, quantum oscillation and angle resolved photoemission spectroscopy (ARPES) experiments have indicated that these Fermi arcs actually represent one side of a Fermi surface reconstructed into nodal hole pockets. These pockets, as well as a number of consequences of their formation, have been shown to be well described by the phenomenological model of Yang Rice and Zhang (YRZ) for the single particle Green's function. Here, we show how the autocorrelation of ARPES spectra - so-called AC-ARPES -- acquired in the normal pseudogap state of the cuprates may be used to examine this phenomenon. [Preview Abstract] |
Tuesday, March 19, 2013 9:12AM - 9:24AM |
F35.00007: Examining Spin Fluctuations Pairing Model From Angle Resolved Photoemission Spectra Vivek Mishra, U. Chatterjee, J.C. Campuzano, M.R. Norman The mechanism of superconductivity is a long standing puzzle in the cuprates. Among various proposed models, pairing through the exchange of spin fluctuations is one of the leading candidates. Here we use spectral functions measured from angle resolved photoemission spectroscopy to calculate this pairing interaction within a random phase approximation, and then determine whether for a reasonable choice of the Hubbard parameter `$U$', we obtain a reasonable $T_c$. [Preview Abstract] |
Tuesday, March 19, 2013 9:24AM - 9:36AM |
F35.00008: Weak doping dependence of nodal transverse velocity in underdoped cuprates: explanation and significant implications Wei Ku Recent high resolution angular resolved photoemission spectroscopy has revealed a surprising nearly doping-independent transverse velocity in the nodal region of underdoped cuprates [1,2], in great contrast to the strong doping dependent superconducting transition temperature. This behavior is qualitatively incompatible with standard Bogoliubov quasi-particle picture currently employed in the field, and implies a fundamentally new regime of physics. Here, we will show analytically that this novel behavior follows naturally the recently derived kinetic nature of the quasi-particle gap in the strong binding limit [3]. This realization further confirms the strong pairing nature of the superconductivity and the novel nature of superconducting gap in underdoped cuprates. This study also suggests the crucial need for future experiments in the overdoped regime. [1] PRL 104, 207002 (2010) [2] PNAS 109, 18332 (2012) [3] PRX 1, 011011 (2011) [Preview Abstract] |
Tuesday, March 19, 2013 9:36AM - 9:48AM |
F35.00009: Deduction of the self-energy and bosonic spectrum of Bi2212 from ARPES experiments Jin Mo Bok, Han-Yong Choi, Junfeng He, X.J. Zhou, Chandra M. Varma We analyzed the ARPES intensity of slightly underdoped ($T_{c}$=89K)and overdoped ($T_{c}$=82K) Bi2212 superconductors. The diagonal and off-diagonal self-energy, $\Sigma$ and $\phi$, were extracted by performing MDC (momentum distribution curve) fitting using superconducting Green's function at the tilt angle $\theta$ with respect to the nodal direction. Using the extracted self-energy as input, the Eliashberg function $\alpha^{2}F^{(+)}$ and $\alpha^{2}F^{(-)}$ corresponding to $\Sigma$ and $\phi$ were deduced by inverting the d-wave Eliashberg equation. Our main results are follows: (1) The deduced Eliashberg functions are similar for slightly underdoped and overdoped Bi2212. (2) The Eliashberg function $\alpha^{2}F^{(+)}$ has two peaks at ~15meV and ~50meV. Both peaks were enhanced as the tilt angle increases or temperature decreases. The Eliashberg function $\alpha^{2}F^{(-)}$ has one peak at ~15meV. Its energy scale is almost the same as the energy scale of the low energy peak of $\alpha^{2}F^{(+)}$. Then, we will compare our results with other experiments and modal calculations. [Preview Abstract] |
Tuesday, March 19, 2013 9:48AM - 10:00AM |
F35.00010: Quantum Monte Carlo simulations of ARPES spectra on correlated materials with electron-phonon coupling Elizabeth Nowadnick, Steven Johnston, Brian Moritz, Richard Scalettar, Thomas Devereaux Results from a variety of experiments have revealed the importance of the electron-phonon interaction in strongly correlated electron materials. In particular, ARPES experiments on the cuprates have observed signatures of polaron formation in the underdoped regime, indicative of strong electron-phonon coupling, as well as ``kinks'' in the dispersion in the doped compounds, which have been interpreted in a phonon picture. In order to study the role of electron-phonon coupling in strongly correlated systems, we simulate the single-band Hubbard-Holstein model using determinant quantum Monte Carlo, an approach that allows the non-perturbative study of strongly interacting systems, and treats the electron-electron and electron-phonon interactions on an equal footing. We present electronic spectral functions, which can be compared to ARPES results, as well as phonon spectral functions, which shed light on phonon renormalizations. In particular, we focus on an antiferromagnetic---charge density wave transition that occurs in the Hubbard-Holstein model at half filling, and present signatures of an emergent intermediate metallic phase that occurs between the two insulating phases. We also discuss the influence of phonons on the electronic dispersion. [Preview Abstract] |
Tuesday, March 19, 2013 10:00AM - 10:12AM |
F35.00011: Phonon-mode couplings studied by pump-probe photoemission Michael Sentef, Alexander Kemper, Brian Moritz, James Freericks, Zhi-Xun Shen, Thomas Devereaux Motivated by recent pump-probe photoemission experiments on cuprate superconductors, we show how the coupling of electrons to phonon modes at the same time leads to a prominent kink in the equilibrium band dispersion and to a distinct behavior of relaxation time scales in nonequilibrium experiments. Here, using the nonequilibrium solution of a model photoexcited electron-phonon system we show that the return of the electrons to equilibrium is governed by the equilibrium self-energy so that the phonon frequency sets a window for``slow'' versus ``fast'' relaxation. The overall structure of the relaxation spectroscopy in the time domain allows for a reliable and quantitative extraction of the electron-phonon coupling strength. [Preview Abstract] |
Tuesday, March 19, 2013 10:12AM - 10:24AM |
F35.00012: Probing Many-Body Interactions in High-Tc Superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ using Time- and Angle-Resolved Photoemission Tristan Miller, Wentao Zhang, Christopher Jozwiak, Christopher Smallwood, Hiroshi Eisaki, Dung-hai Lee, Alessandra Lanzara Laser-based time- and angle-resolved photoemission spectroscopy (trARPES) is a technique that uses an initial laser pulse to pump a system, and a second pulse to probe it by photoemission. By using trARPES on the high temperature superconductor, Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$, we open a window into its many-body quasiparticle interactions. Here we report on the effect of pumping on the quasiparticle band structure of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$. We will discuss the dynamics of this effect, and its relation to the superconducting state. [Preview Abstract] |
Tuesday, March 19, 2013 10:24AM - 10:36AM |
F35.00013: Gap Dynamics in Bi2212 Studied by Time- and Angle-Resolved Photoemission Christopher Smallwood, Wentao Zhang, Tristan Miller, Chris Jozwiak, Hiroshi Eisaki, Alessandra Lanzara Recent developments in ultrafast spectroscopy have shown that irradiating cuprate superconductors with intense, short pulses of light can induce nonequilibrium dynamics that may hold clues for understanding why the critical temperature (Tc) in these materials exceeds that of almost all other superconductors by an order of magnitude or more. Using a 1.5 eV pump pulse, and 5.9 eV probe, we use time- and angle-resolved photoemission spectroscopy (trARPES) to characterize the non-equilibrium dynamics of the gap and transient quasiparticle population in the cuprate superconductor Bi2212 (optimally doped, Tc=91 K). Correlations between these two quantities reveal clues for the underlying mechanism that drives the formation of the pseudogap and superconducting states in the hole-doped cuprates. [Preview Abstract] |
Tuesday, March 19, 2013 10:36AM - 10:48AM |
F35.00014: Time-resolved Ultrafast Spectroscopy Experiments on High Temperature Superconductor Bi2Sr2CaCu2O8 Jianqiao Meng, Georgi L. Dakovski, Jian-Xin Zhu, Peter S. Riseborough, Genda Gu, Steve M. Gilbertson, George Rodriguez, Jingbo Qi, Antoinette Taylor, Tomasz Durakiewicz Time-resolved~ultrafast spectroscopy experiments have been carried out on various dopings of high temperature superconductor Bi2Sr2CaCu2O8In this talk, we will report our observation and analysis of ultrafast dynamics in Bi2Sr2CaCu2O8, with special emphasis on the quasiparticle dynamics in the pseudogap and SC gap regimes. [Preview Abstract] |
Tuesday, March 19, 2013 10:48AM - 11:00AM |
F35.00015: Probing the Nodal Dynamical Electronic States in Bi$_2$Sr$_2$CaCu$_2$O$_8$ by Time- and Angle- Resolved Photoemission Wentao Zhang, Chris Smallwood, Tristan Miller, Chris Jozwiak, Hiroshi Eisaki, Dung-Hai Lee, Alessandra Lanzara Ultra-high resolution time- and angle- resolved photoemission (trARPES) measurements have been carried out on various dopings of Bi$_2$Sr$_2$CaCu$_2$O$_8$ high temperature superconductor. In this talk, we will report on the study of the dynamical quasiparticle excitation and recombination of the nodal electronic states in cuprate. The power of trARPES will be discussed in this talk. [Preview Abstract] |
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