Abstract

Electrons typically traverse a conductive medium in a diffusive manner, resulting in a linear relationship between the measured voltage and applied current – known as Ohm’s law. However, violations of Ohm’s law may be found when the inherent symmetries of the underlying system are broken. Examples include the sliding motion of density waves; ballistic or hydrodynamic electron transport; or the symmetry-breaking realised by lattice or magnetic order. Focused ion beam (FIB) fabrication methods enable precise nanoscale devices to be fashioned from high-quality single crystalline materials, ideal for exploring these nonlinear phenomena. Such nanoengineering offers vast potential for the investigation of both fundamental physics and the development novel quantum devices. In this talk, I will introduce three specific examples. Firstly, we will explore the current-induced sliding motion of a skyrmion lattice in Gd2PdSi3 and the resulting emergent electrodynamics, which originate from a time-dependent Berry phase. Secondly, I will highlight our latest breakthrough to develop FIB fabrication of three dimensional nanostructures, in the form of helical-shaped devices of the high-mobility Weyl magnet CoSn2S2. By breaking inversion symmetry on the length scale of the electron mean free path, we observe large nonreciprocal transport, resulting in a switchable diode effect. Finally, if time permits, I will discuss the possibility to fabricate highly symmetrical devices, which allows the probing of symmetry breaking along multiple directions of a material simultaneously – in this case exploited to study signatures of p-wave magnetism in Gd3Ru4Al12.