In high carrier density correlated electron systems, quantum oscillations are usually detected as tiny oscillations of the magnetization of a sample that appear below 1K. This requires extremely precise and low noise measurement techniques. We have developed a magnetometer based on piezoresistive cantilevers for submilimeter-sized samples with a resolution that is 10-20 times better than previous techniques at 700 mK and in strong magnetic fields. The working principle is based on the use of a SQUID as a low temperature amplifier, which we were able to run in fields up to 15T. [more]
Metallic delafossites are materials which show intriguing properties revealed over the past years. This includes ultra-high conductivity, unconventional magnetism, and the potential to host strongly spin-orbit coupled states at their surfaces and interfaces. Structurally, they are layered materials with triangular in-plane lattices of transition metal atoms. This results in a quasi two-dimensional Fermi surface and very anisotropic transport properties. [more]
Weyl semimetals are materials where valence and conduction bands cross in single points, the Weyl nodes. When the Fermi energy is near these nodes, the electrons effectively behave as relativistic Weyl fermions with a linear energy dispersion and a given chirality. We are searching for experimental signatures of Weyl fermions in bulk probes.
Measurements of the longitudinal magnetoresistance are highly non-trivial, when the anisotropy of the conductivity changes with magnetic field. We investigate this classical effect in the proposed Weyl semimetals and were able to show that the field concentrates the current to a narrow path through the sample in commonly used experimental conditions. We try to overcome this problem in order to determine the intrinsic longitudinal magnetoresistance in Weyl semimetals and hence detect the chiral anomaly. [more]