BoltzTraP. A code for calculating band-structure dependent quantities

It is proposed that when a charge current circulates in a paramagnetic metal a transverse spin imbalance will be generated, giving rise to a ``spin Hall voltage.'' Similarly, it is proposed that when a spin current circulates a transverse charge imbalance will be generated, giving rise to a Hall voltage, in the absence of charge current and magnetic field. Based on these principles we propose an experiment to generate and detect a spin current in a paramagnetic metal.

Spin Hall Effect

Weyl semimetals provide the realization of Weyl fermions in solid-state physics. Among all the physical phenomena that are enabled by Weyl semimetals, the chiral anomaly is the most unusual one. Here, we report signatures of the chiral anomaly in the magneto-transport measurements on the first Weyl semimetal TaAs. We show negative magnetoresistance under parallel electric and magnetic fields, that is, unlike most metals whose resistivity increases under an external magnetic field, we observe that our high mobility TaAs samples become more conductive as a magnetic field is applied along the direction of the current for certain ranges of the field strength. We present systematically detailed data and careful analyses, which allow us to exclude other possible origins of the observed negative magnetoresistance. Our transport data, corroborated by photoemission measurements, first-principles calculations and theoretical analyses, collectively demonstrate signatures of the Weyl fermion chiral anomaly in the magneto-transport of TaAs.

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Signatures of the Adler-Bell-Jackiw chiral anomaly in a Weyl fermion semimetal.

Static critical phenomena in ferromagnets with quenched disorder

The origin of anomalous Hall effect (AHE) in magnetic materials is one of the most intriguing aspects in condensed matter physics and has been a controversial topic for a long time. Recent studies indicate that the intrinsic AHE is closely related to the Berry curvature of occupied electronic states. In a magnetic Weyl semimetal with broken time-reversal symmetry, there are significant contributions to Berry curvature around Weyl nodes, possibly leading to a large intrinsic AHE. Here, we report the quite large AHE in the half-metallic ferromagnet Co3Sn2S2 single crystal. By systematically mapping out the electronic structure of Co3Sn2S2 both theoretically and experimentally, we demonstrate that the intrinsic AHE from the Weyl fermions near the Fermi energy is dominating. The intrinsic anomalous Hall conductivity depends linearly on the magnetization and can be reproduced by theoretical simulation, in which the Weyl nodes monotonically move with the constrained magnetic moment on Co atom.

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Large intrinsic anomalous Hall effect in half-metallic ferromagnet Co 3 Sn 2 S 2 with magnetic Weyl fermions.

1 The Dynamics of Electrons in Metals: Low-Temperature Effects...- 1.1. Theoretical Conditions.- 1.2. Definition of the Hall Effect.- 1.3. Semiclassical Electronic Motion with Electric and Magnetic Fields.- 1.3.1. Compensation in Metals.- 1.4. Quantum Effects.- 1.4.1. Quantum Oscillations.- 1.4.2. Magnetic Breakdown.- 1.5. Size Effects.- 1.5.1. Classical Size Effects.- 1.5.2. Quantum Size Effects.- 2 The Hall Effect in Limiting Cases.- 2.1. The Hall Effect in the Classical High-Field Limit.- 2.1.1. The Hall Effect with No Open Orbits.- 2.1.2. The Hall Effect with Open Orbits.- 2.1.3. Chambers' Expression for the Conductivity Tensor.- 2.2. The Hall Effect in the Low-Field Limit.- 2.2.1. The Case with Localized Magnetic Moments.- 2.2.2. The Low-Field Spin Component.- 2.3. The Hall Effect in the Two-Band Model.- 3 The Hall Effect in Nearly-Free-Electron Metals.- 3.1. Introduction.- 3.2. The Harrison Construction.- 3.3. The Examples of Al and In.- 3.3.1. Case of the High-Field Limit.- 3.3.2. Case of the Low-Field Limit.- 3.3.3. Case of the Intermediate-Field Region.- 4 The Hall Effect in Group 1B Metals.- 4.1. Introduction.- 4.2. The Hall Effect in the Pure Group 1B Metals.- 4.2.1. The Dependence of R on Magnetic Field.- 4.2.2. The Dependence of R on Temperature.- 4.3. The Hall Effect in Very Dilute Alloys.- 4.4. The Hall Effect in Alloys with B-Metal Solutes.- 5 The Hall Effect in Magnetic Metals.- 5.1. Phenomenological Aspects.- 5.2. Some Conduction-Electron Spin Interactions.- 5.3. Survey of the Theoretical Developments.- 5.3.1. Theories with Itinerant Magnetic Carriers.- 5.3.2. Theories with Localized Magnetic Carriers.- 6Experimental Techniques and the Hall Effect in Unusual Conditions.- 6.1. Introduction.- 6.2. Sources of Error.- 6.3. Methods with Electrical Contact to the Sample.- 6.3.1. dc Methods.- 6.3.2. ac Methods.- 6.4. Methods without Contacts.- 6.5. Measurements under Unusual Conditions.- 6.5.1. Measurements at High Pressures.- 6.5.2. Measurements on Liquid Metals.- 6.5.3. The Hall Effect in Superconductors.- 7 A Guide to the Literature for Metallic Elements and Binary Metallic Alloys.- Appendix A Derivation of Expression (2.59).- Appendix B Units and Conversion Factors.- Notes Added in Proof.- Author Index.

Colin M. Hurd

Papers

The Hall effect in metals and alloys