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Search Results: 1 - 10 of 84422 matches for " W. Meevasana "
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Doping dependent optical properties of Bi2201
E. van Heumen,W. Meevasana,A. B. Kuzmenko,H. Eisaki,D. van der Marel
Physics , 2009, DOI: 10.1088/1367-2630/11/5/055067
Abstract: An experimental study of the in-plane optical conductivity of (Pb$_{x}$,Bi$_{2-x}$)(La$_{y}$Sr$_{2-y}$)CuO$_{6+\delta}$ (Bi2201) is presented for a broad doping and temperature range. The in-plane conductivity is analyzed within a strong coupling formalism. We address the interrelationship between the optical conductivity ($\sigma(\omega)$), the single particle self energy, and the electron-boson spectral function. We find that the frequency and temperature dependence can be well described within this formalism. We present a universal description of optical, ARPES and tunneling spectra. The full frequency and temperature dependence of the optical spectra and single particle self-energy is shown to result from an electron-boson spectral function, which shows a strong doping dependence and weak temperature dependence.
Calculation of overdamped c-axis charge dynamics and the coupling to polar phonons in cuprate superconductors
W. Meevasana,T. P. Devereaux,N. Nagaosa,Z. -X. Shen,J. Zaanen
Physics , 2006, DOI: 10.1103/PhysRevB.74.174524
Abstract: In our recent paper we presented empirical evidences suggesting that electrons in cuprate superconductors are strongly coupled to unscreened c-axis polar phonons. In the overdoped regime the c-axis metallizes and we present here simple theoretical arguments demonstrating that the observed effect of the metallic c-axis screening on the polar electron-phonon coupling is consistent with a strongly overdamped c-axis charge dynamics in the optimally doped system, becoming less dissipative in the overdoped regime.
Analysis of the spectral function of Nd1.85Ce0.15CuO4, obtained by angle resolved photoemission spectroscopy
F. Schmitt,W. S. Lee,D. -H. Lu,W. Meevasana,E. Motoyama,M. Greven,Z. -X. Shen
Physics , 2008, DOI: 10.1103/PhysRevB.78.100505
Abstract: Samples of Nd(2-x)Ce(x)CuO(4), an electron-doped high temperature superconducting cuprate (HTSC), near optimal doping at x = 0.155 were measured via angle resolved photoemission (ARPES). We report a renormalization feature in the self energy ("kink") in the band dispersion at 50 - 60 meV present in nodal and antinodal cuts across the Fermi surface. Specifically, while the kink had previously only been seen in the antinodal region, it is now observed also in the nodal region, reminiscent of what has been observed in hole-doped cuprates.
Optical determination of the relation between the electron-boson coupling function and the critical temperature in high T$_c$ cuprates
E. van Heumen,E. Muhlethaler,A. B. Kuzmenko,H. Eisaki,W. Meevasana,M. Greven,D. van der Marel
Physics , 2009, DOI: 10.1103/PhysRevB.79.184512
Abstract: We take advantage of the connection between the free carrier optical conductivity and the glue function in the normal state, to reconstruct from the infrared optical conductivity the glue-spectrum of ten different high-Tc cuprates revealing a robust peak in the 50-60 meV range and a broad con- tinuum at higher energies for all measured charge carrier concentrations and temperatures up to 290 K. We observe that the strong coupling formalism accounts fully for the known strong temperature dependence of the optical spectra of the high Tc cuprates, except for strongly underdoped samples. We observe a correlation between the doping trend of the experimental glue spectra and the critical temperature. The data obtained on the overdoped side of the phase diagram conclusively excludes the electron-phonon coupling as the main source of superconducting pairing.
Spin-orbit splitting of the Shockley surface state on Cu(111)
A. Tamai,W. Meevasana,P. D. C. King,C. Nicholson,A. de la Torre,E. Rozbicki,F. Baumberger
Physics , 2013, DOI: 10.1103/PhysRevB.87.075113
Abstract: We present angle-resolved photoemission data from Cu(111). Using a focused 6 eV continuous wave laser for photo-excitation, we achieve a high effective momentum resolution enabling the first detection of the Rashba spin splitting in the Shockley surface state on Cu(111). The magnitude of the spin-splitting of Delta k ~ 0.006 A^-1 is surprisingly large and exceeds values predicted for the analogous surface state on Ag(111) but is reproduced by first principles calculations. We further resolve a kink in the dispersion which we attribute to electron-phonon coupling.
Superconductivity-Induced Self-Energy Evolution of the Nodal Electron of Optimally-Doped Bi2212
W. S. Lee,W. Meevasana,S. Johnston,D. H. Lu,I. M. Vishik,R. G. Moore,H. Eisaki,N. Kaneko,T. P. Devereaux,Z. X. Shen
Physics , 2008, DOI: 10.1103/PhysRevB.77.140504
Abstract: The temperature dependent evolution of the renormalization effect in optimally-doped Bi2212 along the nodal direction has been studied via angle-resolved photoemission spectroscopy. Fine structure is observed in the real part of the self-energy (Re$\Sigma$), including a subkink and maximum, suggesting that electrons couple to a spectrum of bosonic modes, instead of just one mode. Upon cooling through the superconducting phase transition, the fine structures of the extracted Re$\Sigma$ exhibit a two-processes evolution demonstrating an interplay between kink renormalization and superconductivity. We show that this two-process evolution can be qualitatively explained by a simple Holstein model in which a spectrum of bosonic modes is considered.
Extracting the spectral function of the cuprates by a full two-dimensional analysis: Angle-resolved photoemission spectra of Bi2Sr2CuO6
W. Meevasana,F. Baumberger,K. Tanaka,F. Schmitt,W. R. Dunkel,D. H. Lu,S. -K. Mo,H. Eisaki,Z. -X. Shen
Physics , 2008, DOI: 10.1103/PhysRevB.77.104506
Abstract: Recently, angle-resolved photoemission spectroscopy (ARPES) has revealed a dispersion anomaly at high binding energy near 0.3-0.5eV in various families of the high-temperature superconductors. For further studies of this anomaly we present a new two-dimensional fitting-scheme and apply it to high-statistics ARPES data of the strongly-overdoped Bi2Sr2CuO6 cuprate superconductor. The procedure allows us to extract theself-energy in an extended energy and momentum range. It is found that the spectral function of Bi2Sr2CuO6 can be parameterized using a small set of tight-binding parameters and a weakly-momentum-dependent self-energy up to 0.7 eV in binding energy and over the entire first Brillouin zone. Moreover the analysis gives an estimate of the momentum dependence of the matrix element, a quantity, which is often neglected in ARPES analyses.
Strong electron correlations in the normal state of FeSe0.42Te0.58
A. Tamai,A. Y. Ganin,E. Rozbicki,J. Bacsa,W. Meevasana,P. D. C. King,M. Caffio,R. Schaub,S. Margadonna,K. Prassides,M. J. Rosseinsky,F. Baumberger
Physics , 2009, DOI: 10.1103/PhysRevLett.104.097002
Abstract: We investigate the normal state of the '11' iron-based superconductor FeSe0.42Te0.58 by angle resolved photoemission. Our data reveal a highly renormalized quasiparticle dispersion characteristic of a strongly correlated metal. We find sheet dependent effective carrier masses between ~ 3 - 16 m_e corresponding to a mass enhancement over band structure values of m*/m_band ~ 6 - 20. This is nearly an order of magnitude higher than the renormalization reported previously for iron-arsenide superconductors of the '1111' and '122' families but fully consistent with the bulk specific heat.
Effect of strong correlations on the high energy anomaly in hole- and electron-doped high-Tc superconductors
B. Moritz,F. Schmitt,W. Meevasana,S. Johnston,E. M. Motoyama,M. Greven,D. H. Lu,C. Kim,R. T. Scalettar,Z. -X. Shen,T. P. Devereaux
Physics , 2008, DOI: 10.1088/1367-2630/11/9/093020
Abstract: Recently, angle-resolved photoemission spectroscopy (ARPES) has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the high energy 'waterfall' or high energy anomaly (HEA). This paper demonstrates, using a combination of new ARPES measurements and quantum Monte Carlo simulations, that the HEA is not simply the by-product of matrix element effects, but rather represents a cross-over from a quasiparticle band at low binding energies near the Fermi level to valence bands at higher binding energy, assumed to be of strong oxygen character, in both hole- and electron-doped cuprates. While photoemission matrix elements clearly play a role in changing the aesthetic appearance of the band dispersion, i.e. the 'waterfall'-like behavior, they provide an inadequate description for the physics that underlies the strong band renormalization giving rise to the HEA. Model calculations of the single-band Hubbard Hamiltonian showcase the role played by correlations in the formation of the HEA and uncover significant differences in the HEA energy scale for hole- and electron-doped cuprates. In addition, this approach properly captures the transfer of spectral weight accompanying both hole and electron doping in a correlated material and provides a unifying description of the HEA across both sides of the cuprate phase diagram.
Observation of a robust peak in the glue function of the high-Tc cuprates in the 50-60 meV range
E. van Heumen,E. Muhlethaler,A. B. Kuzmenko,D. van der Marel,H. Eisaki,M. Greven,W. Meevasana,Z. X. Shen
Physics , 2008,
Abstract: We take advantage of the connection between the free carrier optical conductivity and the glue function in the normal state, to reconstruct from the infrared optical conductivity the glue-spectrum of ten different high-Tc cuprates revealing a robust peak in the 50-60 meV range and a broad continuum at higher energies for all measured charge carrier concentrations and temperatures up to 290 K. We observe an intriguing correlation between the doping trend of the experimental glue spectra and the critical temperature.
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