Seminarium Fizyki Materii Skondensowanej

Quantum anomalies is the phenomena that a symmetryclassically present is broken in the quantum theory. The chiralanomaly, in particular, refers to the non-conservation of chiralcharge or current, and has been discussed for example in the contextof the electroweak interactions and neutral superfluid helium. In thesolid state, it has recently been realized that Weyl and Diracsemimetals, in which the conduction and valence points touch in a setof non-degenerate Weyl nodes, have a chiral anomaly. In this contextelectrons with different chirality belong to a different Weyl node,and the chiral anomaly is a mechanism by which parallel electric andmagnetic field pump charge between different Weyl nodes. Due todisorder scattering a characteristic non-equilibrium steady state isobtained. In this talk I will discuss how this state is obtained, whatare its defining features, and how they can be experimentally observedin photoemission spectroscopy [1]. I will also discuss recentexperiments [2] on negative magnetoresistance in Weyl semimetals andtheir relation to the chiral anomaly.[1] Jan Behrends, Adolfo G. Grushin, Teemu Ojanen, Jens H. Bardarson,Visualizing the chiral anomaly in Dirac and Weyl semimetals withphotoemission spectroscopy, arXiv:1503.04329.[2] Chandra Shekhar, Frank Arnold, Shu-Chun Wu, Yan Sun, MarcusSchmidt, Nitesh Kumar, Adolfo G. Grushin, Jens H. Bardarson, RicardoDonizeth dos Reis, Marcel Naumann, Michael Baenitz, Horst Borrmann,Michael Nicklas, Elena Hassinger, Claudia Felser, Binghai Yan, Largeand unsaturated negative magnetoresistance induced by the chiralanomaly in the Weyl semimetal TaP, arXiv:1506.06577.