Inverse Hall Angle Research Articles

Influence of dopants on spin-charge conversion in GaAs

The practical applications for spintronic semiconductors requires the control of spin to charge current conversion. The ratio of spin current to charge current in a material can be determined from the inverse spin Hall angle (θISHE) and can be experimentally extracted. However, the reported results on the magnitude and the sign of θISHE in various semiconductors are rather diversed in association with the difference in the details of material properties. In this study, we focus on the dopant effects on the θISHE of GaAs. We adopted the technique of ferromagnetic resonance driven spin-pumping to accurately determine the θISHE in the GaAs single crystals with different type of dopants. We found that the magnitude of θISHE is sensitive to the atomic number of dopant (Z), but the sign of θISHE is independent on the dopant type. In addition, the relationship between θISHE and Z follows the Landau-Lifshitz Z2 scaling.

Incoherent transport across the strange-metal regime of overdoped cuprates.

Strange metals possess highly unconventional electrical properties, such as a linear-in-temperature resistivity1-6, an inverse Hall angle that varies as temperature squared7-9 and a linear-in-field magnetoresistance10-13. Identifying the origin of these collective anomalies has proved fundamentally challenging, even in materials such as the hole-doped cuprates that possess a simple bandstructure. The prevailing consensus is that strange metallicity in the cuprates is tied to a quantum critical point at a doping p* inside the superconducting dome14,15. Here we study the high-field in-plane magnetoresistance of two superconducting cuprate families at doping levels beyond p*. At all dopings, the magnetoresistance exhibits quadrature scaling and becomes linear at high values of the ratio of the field and the temperature, indicating that the strange-metal regime extends well beyond p*. Moreover, the magnitude of the magnetoresistance is found to be much larger than predicted by conventional theory and is insensitive to both impurity scattering and magnetic field orientation. These observations, coupled with analysis of the zero-field and Hall resistivities, suggest that despite having a single band, the cuprate strange-metal region hosts two charge sectors, one containing coherent quasiparticles, the other scale-invariant 'Planckian' dissipators.

Spin polarized carrier injection driven magneto-optical Kerr effect in Cr-doped ZnO nanorods

Hydrothermal growth of Cr doped ZnO nanorods (NRs) thin films was grown on glass substrates. The strong ferromagnetic (FM) and antiferromagnetic (AFM) ordering was observed in 3% and 7% of Cr doped samples. The optical excitation of the Cr doped ZnO NRs is responsible for injection of the spin-polarized carriers in the 3% Cr doped ZnO NRs through longitudinal magneto-optical Kerr effect (MOKE). We determined a negative anisotropic magnetoresistance (∼23%) originated from spin orbit coupling due to sp-d exchange interaction. we calculated the process of photon induced inverse spin Hall angle (θISHE∼3.94×10−2) close to the MOKE saturated rotation angle (θk∼0.046) for 3% Cr: ZnO. These results can open a new path of optical spin detectors for next-generation spintronic device technology.

Temperature Dependence of In-plane Resistivity and Inverse Hall Angle in NLED Holographic Model**Supported in part by National Natural Science Foundation of China under Grant Nos. 11005016, 11175039, and 11375121

In the strange metal phase of the high-Tc cuprates, it is challenging to explain the linear temperature dependence of the in-plane resistivity and the quadratic temperature dependence of the inverse Hall angle. In this paper, we investigate the temperature dependence of the in-plane resistivity and inverse Hall angle in the nonlinear electrodynamics holographic model developed in our recent work. Maxwell electrodynamics and Born-Infeld electrodynamics are considered. Both cases support a wide spectrum of temperature scalings in parameter space. For Maxwell electrodynamics, the T-linear in-plane resistivity generally dominates at low temperatures and survives into higher temperatures in a narrow strip-like manner. Meanwhile, the T-quadratic inverse Hall angle dominates at high temperatures and extends down to lower temperatures. The overlap between the T-linear in-plane resistivity and the T-quadratic inverse Hall angle, if occurs, would generally present in the intermediate temperate regime. The Born-Infeld case with a > 0 is quite similar to the Maxwell case. For the Born-Infeld case with a < 0, there can be a constraint on the charge density and magnetic field. Moreover, the overlap can occur for strong charge density.

Magnetothermoelectric DC conductivities from holography models with hyperscaling factor in Lifshitz spacetime

We investigate an Einstein–Maxwell-Dilaton–Axion holographic model and obtain two branches of a charged black hole solution with a dynamic exponent and a hyperscaling violation factor when a magnetic field presents. The magnetothermoelectric DC conductivities are then calculated in terms of horizon data by means of holographic principle. We find that linear temperature dependence resistivity and quadratic temperature dependence inverse Hall angle can be achieved in our model. The well-known anomalous temperature scaling of the Nernst signal and the Seebeck coefficient of cuprate strange metals are also discussed.

Hyperscaling violating black hole solutions and magneto-thermoelectric DC conductivities in holography

We derive new black hole solutions in Einstein-Maxwell-Axion-Dilaton theory with a hyperscaling violation exponent. We then examine the corresponding anomalous transport exhibited by cuprate strange metals in the normal phase of high-temperature superconductors via gauge/gravity duality. Linear temperature dependence resistivity and quadratic temperature dependence inverse Hall angle can be achieved. In the high temperature regime, the heat conductivity and Hall Lorenz ratio are proportional to the temperature. The Nernst signal first increases as temperature goes up but it then decreases with increasing temperature in the high temperature regime.

DC and Hall conductivity in holographic massive Einstein-Maxwell-Dilaton gravity

We investigate the holographic DC and Hall conductivity in massive Einstein-Maxwell-Dilaton (EMD) gravity. Two special EMD backgrounds are considered explicitly. One is dyonic Reissner-Nordstr$\ddot{o}$m-AdS (RN-AdS) geometry and the other one is hyperscaling violation AdS (HV-AdS) geometry. We find that the linear-T resistivity and quadratic-T inverse Hall angle can be simultaneously achieved in HV-AdS models, providing a hint to construct holographic models confronting with the experimental data of strange metal in future.

Strange metals at finite ’t Hooft coupling

In this paper, we consider the AdS–Schwarzschild black hole in light-cone coordinates which exhibits non-relativistic z=2 Schrodinger symmetry. Then, we use the AdS/CFT correspondence to investigate the effect of finite-coupling corrections to two important properties of the strange metals which are the Ohmic resistivity and the inverse Hall angle. It is shown that the Ohmic resistivity and inverse Hall angle are linearly and quadratically temperature dependent in the case of $\mathcal{R}^{4}$ corrections, respectively, while in the case of Gauss–Bonnet gravity, we find that the inverse Hall angle is quadratically temperature dependent and the Ohmic conductivity can never be linearly temperature dependent.

Holographic quantum criticality and strange metal transport

A holographic model of a quantum critical theory at a finite but low temperature and a finite density is studied. The model exhibits non-relativistic z = 2 Schrödinger symmetry and is realized by the anti-de-Sitter–Schwarzschild black hole in light-cone coordinates. Our approach addresses the electrical conductivities in the presence or absence of an applied magnetic field and contains a control parameter that can be associated with quantum tuning via charge carrier doping or an external field in correlated electron systems. The Ohmic resistivity, the inverse Hall angle, the Hall coefficient and magnetoresistance are shown to be in good agreement with experimental results of strange metals at very low temperature. The holographic model also predicts new scaling relations in the presence of a magnetic field.

The normal state scattering rate in high- cuprates

I present a new phenomenological model for the normal state transport properties of high-Tc cuprates. In particular, I identify a form of scattering rate that may account, qualitatively and quantitatively, for the normal state (magneto)-transport properties of Tl2Ba2CuO6+\delta and Bi2Sr2CaCu2O8+\delta from optimal doping through to the overdoped side of the phase diagram. The form of the scattering rate is also consistent with features seen in photoemission spectroscopy in Bi2Sr2CaCu2O8+\delta and offers a new intuitive way to understand the evolution of the temperature dependence of the inverse Hall angle with disorder and with carrier concentration.

Small-angle scattering in a marginal Fermi liquid

We study the magnetotransport properties of a model of small-angle scattering in a marginal Fermi liquid. Such a model has been proposed by Varma and Abrahams [Phys. Rev. Lett. 86, 4652 (2001)] to account for the anomalous temperature dependence of in-plane magnetotransport properties of the high-Tc cuprates. We study the resistivity, Hall angle and magnetoresistance using both analytical and numerical techniques. We find that small-angle scattering only generates a new temperature dependence for the Hall angle near particle-hole symmetric Fermi surfaces where the conventional Hall term vanishes. The magnetoresistance always shows Kohler's rule behavior.

Effect of Fermi surface destruction on transport properties in underdoped cuprates

Motivated by recent experimental measurements on the Fermi surface(FS) destruction in underdoped high-$T_{c}$ cuprates, we examine its effect on the transport properties based on the Boltzmann equation approach. The effect is modeled by simply taking the density of states for electrons in the gapped regions to be zero. Within the nearly antiferromagnetic Fermi liquid model, we calculate the temperature dependences of the dc resistivity, the inverse Hall angle and the Hall coefficient. It is shown that the effect of the FS destruction on transport properties is sensitive to the existance and the range of the flat band near $(0,\pm\pi)$ in the dispersion of electrons, and the anistropy of the relaxation rate along the Fermi surface. We find that the experimental data are better described by the cold spot model, i.e., the transports are determined mainly by the contribution of the electrons near the Brillouin-zone diagonals.

Hall effect of single layer, tetragonal Tl 2Ba 2CuO 6+δ near optimal doping

We report measurements of the Hall effect in single crystals of Tl 2Ba 2CuO 6+δ near optimum doping. In principle, this is an ideal material for an investigation of the quality of the well-known linear and quadratic temperature dependences of the resistivity and inverse Hall angle, since crystals of this material have a simple tetragonal crystal structure with one CuO 2 layer per formula unit, and little disorder.

Hall effect measurements on ion bombarded YBaCuO films

High quality c-axis oriented YBaCuO films, epitaxially grown on (100) SrTiO 3 substrates, were photolithographically patterned to allow Hall measurements at different temperatures 4K≦T≦300K in magnetic fields up to B≦5 T aligned parallel to the surface normal. In this way, the temperature and field dependence of the longitudinal ϱ xx(B,T) and transverse resistivity ϱ xy(B,T)] were determined before and after irradiation with 350 keV He + ions. The resulting changes of the temperature dependence of the longitudinal resistivity, Hall resistivity and inverse Hall angle are reported.