Thermodynamic signatures of topological spin-texture transitions in magnetic field gradients
- Topological phases are commonly characterized by a non-trivial Chern number which is related in many cases to non-trivial topological spin-textures. There are measurable quantities, such as the transverse Hall conductivity, being proportional to the Chern number. The transverse Hall conductivity is a transport quantity depending on edge state physics. In contrast to these transport quantities, thermodynamic response signatures unequivocally indicating topological spin-texture transitions are investigated in this thesis. These signatures are bulk properties, analyzed in two dimensional electronic systems where the information about non-trivial topological phase transitions are manifest in the second order response of the spin polarization to external in-plane magnetic field gradients. This response is shown to directly provide topological information.In addition, the change in the spin magnetization due to the magnetic field gradients shows a clear increase in its amplitude towards theTopological phases are commonly characterized by a non-trivial Chern number which is related in many cases to non-trivial topological spin-textures. There are measurable quantities, such as the transverse Hall conductivity, being proportional to the Chern number. The transverse Hall conductivity is a transport quantity depending on edge state physics. In contrast to these transport quantities, thermodynamic response signatures unequivocally indicating topological spin-texture transitions are investigated in this thesis. These signatures are bulk properties, analyzed in two dimensional electronic systems where the information about non-trivial topological phase transitions are manifest in the second order response of the spin polarization to external in-plane magnetic field gradients. This response is shown to directly provide topological information.In addition, the change in the spin magnetization due to the magnetic field gradients shows a clear increase in its amplitude towards the phase boundary with a sign change across the phase transition. The results demonstrate that the magnetization response can in principle be in measurable ranges and therefore appropriate to gain qualitative information about changes in topological invariants across the phase transitions.…
