Domain walls are 2D interfaces separating regions with different direction of the order parameter in 3D materials. Atomically sharp conductive domain walls, emering in otherwise insulating materials, show fascinating electronic functionalities not present in the bulk. In spite of the great interest in such domain walls, our knowledge about the microscopic mechanisms behind their conduction is rather superficial. In addition to the information obtained from its mean value, the fluctuations of the conductance can give further insight into nature of the charge transport. Along this line, the PhD student will perform noise spectroscopy measurements to determine the frequency dependence of the conductance noise both in the linear and non-linear response regimes. In the target material class, the ferroelectric lacunar spinels, the density of the conductive domain walls can be controlled by either electric or magnetic fields. This gives a unique possibility to distinguish the electrical noise of the domain walls from noise from other sources. We expect that the analysis of the noise spectra can reveal fundamental aspects of the domain-wall conduction in this material class. Since domain-wall kinetics, namely thermal fluctuations, slow rearrangements and pinning of the wall, can strongly influence the conduction properties, we shall also get insight into these microscopic processes.
 

The PhD research is planned as a bilateral project taking place in part time at Budapest University of Technology and Economics and at University of Augsburg, under the supervisions of A. Halbritter and I. Kézsmárki, respectively.