This thesis investigates the electrical resistance of three classes of materials under the influence of high magnetic fields and uniaxial strain. Firstly, the semiconductors InSb and InAs, and the topological metal ZrTe₅, are examined. These materials share the property of undergoing a metal-to-insulator transition under high magnetic fields, although this is still disputed for ZrTe₅. We investigate the stability of the high-field state of these materials under the influence of uniaxial strain. We then focus on the magnetoresistance – the change in resistance under a magnetic field – of NbSe₂. In contrast to the conventional, quadratic magnetoresistance, that in NbSe₂ is quadratic-to-linear. Using a recently published model, we link this to the influence of the charge-density-wave state that forms in NbSe₂ at low temperatures, by postulating that this causes a strong increase in electron scattering at specific locations on the Fermi surface. Finally, we study the exotic material Li₀.₉Mo₆O₁₇, which is a candidate for realising a conductive Tomonaga–Luttinger liquid state. Following a comprehensive introduction, we discuss a measurement of the angular dependence of the Hall effect, and the effect of uniaxial strain along different crystal axes on the resistance. We interpret our data in the context of a recently published model based on the formation of dark excitons.
Arwin Kool is a fourth-year PhD student at HFML-FELIX, supervised by Nigel Hussey and Steffen Wiedmann. He obtained his Bachelor’s degree in Physics and Astronomy (2019) and his Master’s degree in Physics of Molecules and Materials (2021) at Radboud University. His research focuses on investigating the electronic state of solids by measuring their electrical resistance in high magnetic fields and under uniaxial strain. He has also assisted various visiting researchers in carrying out their experiments in the high-field facility at the HFML, including work on measuring quantum oscillations, thin-film devices and materials under high hydrostatic pressure.