Terahertz Hall Measurements On Optimally Doped Single Crystal Bi-2212

The infrared Hall angle in optimally doped single crystal $\rm Bi_2 Sr_2 Ca Cu_2 O_{8+x}$ was measured from 3.05 to 21.75 meV as a continuous function of temperature from 25 to 300\,K. In the normal state, the temperature dependence of the real part of the cotangent of the infrared Hall angle obeys the same power law as dc measurements. The measured Hall frequency $\rm \omega_H$ is significantly larger than the expected value based upon ARPES data analyzed in terms of the relaxation time approximation. This discrepancy as well as the temperature dependence of $\rm Re(\cot{\theta_H})$ and $\omega_H$ is well described by a Fermi liquid theory in which current vertex corrections produced by electron-magnon scattering are included.Comment: 10 pages, 2 figure

Terahertz Kerr and Reflectivity Measurements on the Topological Insulator Bi2Se3

We report the first terahertz Kerr measurements on bulk crystals of the topological insulator Bi2Se3. At T=10K and fields up to 8T, the real and imaginary Kerr angle and reflectance measurements utilizing both linearly and circularly polarized incident radiation were measured at a frequency of 5.24meV. A single fluid free carrier bulk response can not describe the line-shape. Surface states with a small mass and surprisingly large associated spectral weight quantitatively fit all data. However, carrier concentration inhomogeneity has not been ruled out. A method employing a gate is shown to be promising for separating surface from bulk effects.Comment: 10 pages, 5 figure

Infrared Hall conductivity of Na0.7_{0.7}CoO2_2

We report infrared Hall conductivity $\sigma_{xy}(\omega)$ of Na$_{0.7}$CoO$_2$ thin films determined from Faraday rotation angle $\theta_{F}$ measurements. $\sigma_{xy}(\omega)$ exhibits two types of hole conduction, Drude and incoherent carriers. The coherent Drude carrier shows a large renormalized mass and Fermi liquid-like behavior of Hall scattering rate, $\gamma_{H} \sim aT^{2}$. The spectral weight is suppressed and disappears at T = 120K. The incoherent carrier response is centered at mid-IR frequency and shifts to lower energy with increasing T. Infrared Hall constant is positive and almost independent of temperature in sharp contrast with the dc-Hall constant.Comment: 5 Pages, 5 Figures. Author list corrected in metadata only, paper is unchange

Origin of the anomalous Hall Effect in overdoped n-type cuprates: current vertex corrections due to antiferromagnetic fluctuations

The anomalous magneto-transport properties in electron doped (n-type) cuprates were investigated using Hall measurements at THz frequencies. The complex Hall angle was measured in overdoped Pr$_{\rm 2-x}$Ce$_{\rm x}$CuO$_{\rm 4}$ samples (x=0.17 and 0.18) as a continuous function of temperature above $T_c$ at excitation energies 5.24 and 10.5 meV. The results, extrapolated to low temperatures, show that inelastic scattering introduces electron-like contributions to the Hall response. First principle calculations of the Hall angle that include current vertex corrections (CVC) induced by electron interactions mediated by magnetic fluctuations in the Hall conductivity reproduce the temperature, frequency, and doping dependence of the experimental data. These results show that CVC effects are the source of the anomalous Hall transport properties in overdoped n$\text{-}$type cuprates.Comment: 5 pages, 3 figure

Magneto-optical evidence for a gapped Fermi surface in underdoped YBa2Cu3O6+x

The infrared (900-1100 cm-1) Faraday rotation and circular dichroism are measured in the normal state of underdoped High Tc superconductors and used to study the magneto-transport. YBa2Cu3O6+x thin films are investigated in the temperature range 10-300 K in magnetic fields up to 8 Tesla and as a function of oxygen concentration. A dramatic increase of the Hall frequency is observed for underdoped samples which is not consistent with the approach to a Mott transition but is consistent with a partial gapping of the Fermi surface as predicted in charge density wave models.Comment: 14 pages, 4 figure