Riassunto analitico
When materials are subjected to a magnetic field, electrons occupy orbits with discrete energy levels which are referred to as Landau levels (LLs). In case the magnetic field is very high, a material enters the so-called quantum limit, where all the charge carriers are confined in the lowest LL while the kinetic energy is quenched.
In this regime, various electronic transitions and field-induced many-body phenomena may occur. In narrow-gap semiconductors and quantum materials, a metal-insulator transition (MIT), a magnetic freeze-out and the Anomalous Hall Effect (AHE) have been observed.
In this thesis, we study the behaviour of low-doped, narrow-gap semiconductors InAs and InSb with different doping concentrations, and the topological material ZrTe5 in magnetic fields up to 35 T. In particular, we focus on the effects of uniaxial strain on the electronic properties of these materials to investigate how this affects the MIT and the AHE.
For InAs and InSb, we observe a distinct behaviour in the magnetic freeze-out regime, while the response of the MIT to strain is qualitatively similar. In particular, in InSb, we see a sign change that could be explained in terms of AHE and compensation of charge carriers in high fields. In ZrTe5, we measure a maximum in the Hall Signal that displays a sign change at low temperatures, which is highly sensitive to the application of uniaxial strain. Furthermore, we show that the absolute value of the AHE of ZrTe5 is not affected by strain.
The experiments performed on these samples allow us to gain a deeper insight into the physics of the field-induced states that take place in the quantum limit of the investigated materials and to understand the underlying mechanisms that drive these physical phenomena. Moreover, we show that uniaxial strain can be employed to tune the electronic structure of materials, thus being a promising tool to probe and investigate the behaviour of electronic transitions in different materials.
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