Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session R38: Superconductivity-Optical Spectroscopy of Cuprates: IR Hall Effect |
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Sponsoring Units: DCMP Chair: John Cerne, University at Buffalo, SUNY Room: Baltimore Convention Center 341 |
Wednesday, March 15, 2006 2:30PM - 2:42PM |
R38.00001: Strong correlation effects in the IR Hall Effect in the cuprates: an overview H.D. Drew The Hall Effect at infrared frequencies provides a sensitive probe of strong interaction effects in strongly correlated metals. Experimental results show that the strong interaction effects inter the Hall conductivity and the optical conductivity differently in the cuprates [1,2,3]. For hole doping the Hall angle at mid IR frequencies is nearly simple Drude but with a scattering rate that is nearly frequency dependent in contrast to the optical conductivity [1]. The Hall frequency is in good agreement with ARPES results at optimal doping but increases rapidly for underdoped samples in contrast to expectations from ARPES [1,2]. The electron doped cuprates show evidence for density wave gap excitations and are non Drude-like even outside the density wave regime of doping and temperature [3]. A recent theoretical analysis based on the exchange of magnetic excitations that includes vertex corrections in the conductivity appears to account for many of these observations [4]. \newline [1] DC Schmadel, et al., cond-mat/0510793.\newline [2] L Shi, et al., cond-mat/0510794.\newline [3] A Zimmers, et al., cond-mat/0510085.\newline [4] H Kontani, cond-mat/0507664. [Preview Abstract] |
Wednesday, March 15, 2006 2:42PM - 2:54PM |
R38.00002: Significant Role of Current Vertex Correction in Optical Conductivity of Strongly Correlated Systems. Seiichiro Onari, Hiroshi Kontani Based on the microscopic Fermi liquid theory, we study DC and AC transport phenomena in strongly correlated systems. We take the current vertex correction (CVC), which is called the backflow in the phenomenological Fermi liquid theory, into account correctly to satisfy the conservation laws. In the vicinity of the antiferromagnetic (AF) quantum critical point (QCP), various transport coefficients show striking deviations from the Fermi liquid-type temperature dependences due to the CVC. Moreover, we find that the frequency dependence of the CVC gives rise to striking deviations of the optical conductivities from the conventional extended-Drude-type functions, when systems is close to the AF-QCP. We explain the important effect of the CVC on the temperature- and frequency-dependences of $\sigma (\omega )$ and $\sigma _{xy} (\omega )$ in strongly correlated systems. [Preview Abstract] |
Wednesday, March 15, 2006 2:54PM - 3:06PM |
R38.00003: Theory of Optical Conductivity and Hall Conductivity in High-Tc Superconductors Hiroshi Kontani We study AC conductivities in high-Tc cuprates, which offer us significant information to determine the true ground states. We take the current vertex correction (CVC) into account correctly to satisfy the conservation laws in terms of the fluctuation-exchange (FLEX) approximation. The significant role of the CVC on the optical Hall conductivity,$\sigma _{xy} (\omega )$, is confirmed in the presence of strong antiferromagnetic (AF) fluctuations. This fact leads to the failure of the relaxation time approximation (RTA). As a result, experimental highly unusual behaviors, (i) prominent $\omega $ and temperature dependences of the optical Hall conductivity and the optical Hall coefficient,$R_H (\omega )$, and (ii) a simple Drude form of the optical Hall angle,$\theta _H (\omega )$, for a wide range of $\omega $, are satisfactorily reproduced. In conclusion, both DC and AC transport phenomena in (slightly under-doped) high-Tc cuprates can be explained comprehensively in terms of a nearly AF Fermi liquid, without assuming an exotic ground state. [Preview Abstract] |
Wednesday, March 15, 2006 3:06PM - 3:18PM |
R38.00004: The mid-infrared Hall effect in optimally-doped Bi$_{2}$Sr$_{2}$CaCu$_2$O$_{8+\delta}$ Don Schmadel, Genda Gu, H.D. Drew Heterodyne polarometry is used to measure the frequency dependence in the mid IR from 900 to 1100 cm$^-1$ and temperature dependence from 35 to 330 K of the normal state Hall transport in single crystal, optimally doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$. The results show a simple Drude behavior in the Hall conductivity $\sigma_{xy}$ which stands in contrast to the more complex, extended Drude behavior for the longitudinal conductivity $\sigma_{xx}$. The mid IR Hall scattering rate $\gamma_{xy}$ increases linearly with temperature and has a small, positive, projected intercept at $T=0$. The longitudinal scatter rate, in contrast, is much larger and exhibits very little temperature dependnece. The Hall frequency indicates a carrier mass which is 6.7 times the band mass and which decrease slighly with increasing frequency. These disparate behaviors are consistent with calculations based on the fluctuation-exchange interaction using current vertex corrections (H Kontani, cond-mat/0507664). [Preview Abstract] |
Wednesday, March 15, 2006 3:18PM - 3:30PM |
R38.00005: Infrared Hall effect in underdoped and optimally doped La$_{2-x}$Sr$_x$CuO$_4$ Lingyun Shi, D. Schmadel, H.D. Drew, I. Tsukada, Y. Ando We report a study of magneto-optical properties in the mid-infrared region of a series of La$_{2-x}$Sr$_x$CuO$_4$ samples with hole doping level ranging from severely underdoped ($x=0.03$)to optimally doped ($x=0.15$). The Faraday rotation and circular dichroism are measured in a magnetic field of 8 Tesla and in a temperature range between 30K and 300K. The doping and temperature dependence of infrared Hall angle is found to be consistent with a simple Drude model. A significant increase of Hall frequency is observed when the hole doping level is reduced from optimal doping, which is consistent with a drastic reduction of the volume of Fermi surface in the underdoped sample. These results are similar to results of an earlier study of underdoped YBa2Cu3O6+x [L. B. Rigal, et al., Phys. Rev. Lett. 93,137002 (2004)]. Both experiments will be compared with theoretical models of the IR Hall effect. [Preview Abstract] |
Wednesday, March 15, 2006 3:30PM - 3:42PM |
R38.00006: Far IR Hall Angle Measurements on Single Crystal Bi$_2$Sr$_2$CaCu$_2$0$_{8+x}$. Gregory Jenkins, D.C. Schmadel, H.D. Drew, Genda Gu The far-infrared complex Hall angle was studied in thin optimally doped single crystal Bi$_2$Sr$_2$CaCu$_2$0$_{8+x}$ as a continuous function of temperature from 25 to 300 K and at a discrete set of frequencies in the range of 25 cm$^{-1}$ to 175 cm $^{-1}$ using a heterodyne technique. The real part of the inverse Hall angle obeys a temperature power law, T$^{n}$, where n = 1.65 which is consistent with the dc-value. For the three frequencies below 90 cm$^{-1}$, the Hall frequency is a constant in temperature and frequency to within 20\% from T$_C$ up to room temperature. The Hall mass of 2.5 m$_e$ in reasonable agreement with the values found in far IR optical measurements 3.0 m$_e$, ARPES dispersion results along the $(\pi,\pi)$ nodal direction (2.9 m$_e$), and mid IR Hall measurements (2.8 m$_e$) where m$_e$ is the bare electron mass. These results will be compared with theoretical predictions. [Preview Abstract] |
Wednesday, March 15, 2006 3:42PM - 3:54PM |
R38.00007: Infrared Hall Effect in the electron-doped high $T_c$ cuprate Pr$_{2-x}$Ce$_{x}$CuO$_4$ A. Zimmers, L. Shi, D. C. Schmadel, W. M. Fisher, R. L. Greene, H. D. Drew We have performed infrared Hall measurements ($\sigma_{xy}$) as a function of temperature, frequency (950-1100~cm$^{-1}$) and wide doping range of Pr$_{2-x}$Ce$_{x}$CuO$_4$. Previous measurements have shown that electron-doped materials present clear evidence for a gap in the $\sigma_{xx}$ spectrum [1] and the DC Hall effect [2] for samples below both a critical doping of $x_c\sim$ 0.17, a characteristic temperature $T_W$ and an energy $\omega_W$. Our results lend further support to a density wave state in underdoped PCCO. However, these results demonstrate that $\sigma_{xy}$ exhibits strong deviations from the extended Drude model in contrast to its success for $\sigma_ {xx}$ in overdoped Pr$_{2-x}$Ce$_{x}$CuO$_4$ and in hole-doped cuprates. The work at University of Maryland was supported by NSF grants DMR-0352735 and DMR-0303112. [1] A. Zimmers $et$ $al$., Europhys. Lett., \textbf{70} (2), 225 (2005). [2] Y. Dagan $et$ $al$., Phy. Rev. Lett. \textbf{92}, 167001 (2004). [Preview Abstract] |
Wednesday, March 15, 2006 3:54PM - 4:06PM |
R38.00008: Extended frequency dependence of the infrared Hall Effect in electron-doped high T$_c$ cuprate Pr$_{2-x}$Ce$_x$CuO$_4$ M. Houseknecht, G. Acbas, M.-H. Yang, J. Cerne, A. Zimmers, L. Shi, D.C. Schmadel, R.L. Greene, H.D. Drew Although the infrared longitudinal conductivity $\sigma_{xx}$ in Pr$_{2-x}$Ce$_x$CuO$_4$ can be modeled using a Drude model which includes density wave (DW) excitations at low temperatures and low doping concentrations (Zimmers, PRB 2004), the infrared Hall conductivity $\sigma_{xy}$ exhibits behavior (Zimmers, cond-mat/0510085) that is not consistent with this model even outside of the DW phase. By measuring the rotation and ellipticity of the polarization of transmitted light through a sample in magnetic fields up to 7 T, the infrared Faraday angle is determined in the 115 to 366 meV (930-3000 cm$^{-1}$) energy range. The Faraday angle is closely related to the Hall angle and $\sigma_{xy}$, which provide a sensitive test of the many-body interactions that could lead to deviations from Drude behavior. Three samples with doping levels of $x =$ 0.12, 0.15 and 0.18 are probed at temperatures ranging from 50 K to 300 K. Non-Drude behavior is observed in the Faraday angle, which also changes sign as a function of frequency and temperature from electron-like to hole-like as expected from the hole-like underlying Fermi surface. Supported by the Research Corporation Cottrell Scholar Award (UB), NSF CAREER Award (UB), NSF DMR-0352735 (UMCP) and NSF DMR-0303112 (UMCP). [Preview Abstract] |
Wednesday, March 15, 2006 4:06PM - 4:18PM |
R38.00009: Raman scattering study of low energy charge dynamics in the normal state of Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$ G. Blumberg, B. S. Dennis, M. M. Qazilbash, R. L. Greene Some of the normal state properties of the electron-doped (n-doped) superconducting cuprates R$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$(R = La, Pr, Nd, Sm) are different from those of the hole-doped (p-doped) cuprates. In the n-doped cuprates at optimal doping (x = 0.15) the dc resistivity is a quadratic function of temperature whereas in the p-doped cuprates it is linear in temperature. The charge carriers in p-doped cuprates are holes whereas in the n-doped cuprates both electronlike and holelike carriers exist near optimal doping; the electronlike carriers reside near ($\pm \pi $/a, $\pm \pi $/4a) and ($\pm \pi $/4a, $\pm \pi $/a) regions and the holelike carriers reside near ($\pm \pi $/2a, $\pm \pi $/2a) regions of the Brillouin Zone. We have performed temperature and doping dependent Raman scattering study in the normal state of the n-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$. Using polarized light we have isolated the low energy dynamics of the electronlike and holelike carriers. We compare Raman data in the B$_{1g}$ and B$_{2g}$ channels to dc resistivity and discuss the implications. [Preview Abstract] |
Wednesday, March 15, 2006 4:18PM - 4:30PM |
R38.00010: Theory of Low-Temperature Hall Effect in Electron-Doped Cuprates Jie Lin, Andrew Millis A mean field calculation of the $T\rightarrow 0$ limit of the Hall conductance of electron-doped cuprates such as $Pr_{2-x}Ce_xCuO_{4+\delta}$ is presented. The data are found to be qualitatively consistent with the reconstruction of the Fermi surface expected upon density wave ordering. The magnitude of the density wave gap is found to be large. The Hall resistance exhibits a nonanalyticity at the quantum critical point for density wave ordering, but the amplitude of the anomaly is found to be unobservably small. The quantum critical contribution to $R_H(B)$ is determined. Quantitative discrepancies between calculation and data remain, suggesting that the experimental doping is not identical to the $Ce$ concentration $x$. [Preview Abstract] |
Wednesday, March 15, 2006 4:30PM - 4:42PM |
R38.00011: Infrared Hall effect measurement of correlated metal Na$_{0.75}$CoO$_2$ E.J. Choi, A. Zimmers, L. Shi, A. Soushkov, H.D. Drew, J.H. Cho Na$_{x}$CoO$_2$ has a layered Co-O plane where Co ions form a triangular bonding block in contrast with the square Cu moments of HTSC Cu-O plane. With varying x, the compound exhibits rich phases like superconductivity (x=0.3, H$_2$O intercalted), charge-ordering (x=0.5) and Curie-Weiss metal (x$\sim$0.7). Na$_{x}$CoO$_2$ thin film (x=0.75) was grown on SrTiO$_3$ substrate using PLD method. Resistivity and dc-Hall effect show same temperature dependence as those of single crystal. We studied ac Hall effect by measuring the complex Faraday rotation $\theta_{F}$ at infrared frequency ( 1100 cm$^{-1}$) for 30K$>$T$<$300K and in magnetic fields up to 8 Tesla. As T decreases, real part of $\theta_{F}$ shows a slop change where dRe($\theta_{F}$)/dT from negative to positive sign at T=100K. At the same T, Im($\theta_{F}$)shows a dispersive structure. This anomaly comes from $\sigma_xy$ while $\sigma_xx$ is monotonic with T. Possible origin of the unusual infrared Hall conductivity sigma$_xy$ is considered in terms of spin density wave, Na-ordering, and electronic Kagome lattice. [Preview Abstract] |
Wednesday, March 15, 2006 4:42PM - 4:54PM |
R38.00012: Magneto-optical studies of high-T$_c$ cuprates in 33 Tesla S.V. Dordevic, A. Gozar, I. Bozovic, C.C. Homes, G.D. Gu, W. Si, Y.J. Wang We will report results of our magneto-optical studies of high- T$_c$ cuprates in high magnetic field. An optimally doped LSCO thin film with thickness of 78 nm and T$_c$ = 41 K was studied in transmission geometry with magnetic field of 33 Tesla. The measurements have been performed in the mid-IR part of the spectrum, and at temperatures both below and above Tc. In addition, several other cuprates families, such as YBCO, Bi2212, LBCO and NCCO, have been studied in reflection geometry, with magnetic field of 18 Tesla applied perpendicular to CuO$_2$ planes. In all studied samples we find extreme insensitivity of optical properties to external magnetic field. The results will be discussed in the context of existing theoretical models. [Preview Abstract] |
Wednesday, March 15, 2006 4:54PM - 5:06PM |
R38.00013: c-axis magneto optics and vortex dynamics of underdoped YBCO A.D. LaForge, K.S. Burch, W.J. Padilla, Kouji Segawa, Yoichi Ando, D.N. Basov c-axis reflectance measurements have been carried out on high quality single crystals of YBa$_{2}$Cu$_{3}$O$_{x }$at two dopings, x = 6.65 and x = 6.75, with magnetic fields oriented both parallel and perpendicular to the CuO$_{2}$ plane. Fields applied parallel to the plane induced several interesting effects at temperatures below the superconducting transition, including a strong suppression of superfluid density and the appearance of a new mode at frequencies below the Josephson plasma resonance (JPR). This mode is field-dependent both in magnitude and position, shifting to higher energies with increasing field. Here it is analyzed within several models of vortex dynamics, including that of Tachiki, Koyama, and Takahashi. Application of fields perpendicular to the plane creates a shift in the JPR frequency, as predicted by the TKT model. [Preview Abstract] |
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