Electrical resistance of magnets with and without electron collisions
Electrical resistance R of metals arises from collisions of the conduction electrons with obstacles in the surrounding material and from the mass of the electrons. Interestingly, in a magnetic metal, R is larger when the current flows parallel to the magnetic moment M (see Figure (a), left), and it is smaller when the electrons flow perpendicular to it (Figure (b), left). This “anisotropic magnetoresistance” (AMR) is a mature effect, which is usually explained by the assumption that electrons moving parallel to M [more...]

The transport of electrons is governed by the shape of the Fermi surface. We found that the topology of the Fermi surface of a semimetal can be manipulated on ultrafast timescales through optical excitation. A change in the Fermi surface topology, also called Lifshitz transition, can lead to the emergence of fascinating phenomena like colossal magnetoresistance and superconductivity. Combining time-resolved multidimensional photoemission spectroscopy and TDDFT+U simulations, we introduce a scheme for driving an ultrafast Lifshitz [more...]