Robert Zielke
ContactDepartment of PhysicsUniversity of Basel Klingelbergstrasse 82 CH4056 Basel, Switzerland

Short CV
2009  present  PhD student at the University of Basel 
2009  M.Sc. in Physics, University of Basel 
Publications
Show all abstracts.1.  Anisotropic g factor in InAs selfassembled quantum dots 
Robert Zielke, Franziska Maier, and Daniel Loss. Phys. Rev. B 89, 115438 (2014); arXiv:1311.0908.
We investigate the wave functions, spectrum, and gfactor anisotropy of lowenergy electrons confined to selfassembled, pyramidal InAs quantum dots (QDs) subject to external magnetic and electric fields. We present the construction of trial wave functions for a pyramidal geometry with hardwall confinement. We explicitly find the ground and first excited states and show the associated probability distributions and energies. Subsequently, we use these wave functions and 8band $k\cdot p$ theory to derive a Hamiltonian describing the QD states close to the valence band edge. Using a perturbative approach, we find an effective conduction band Hamiltonian describing lowenergy electronic states in the QD. From this, we further extract the magnetic field dependent eigenenergies and associated g factors. We examine the g factors regarding anisotropy and behavior under small electric fields. In particular, we find strong anisotropies, with the specific shape depending strongly on the considered QD level. Our results are in good agreement with recent measurements [Takahashi et al., Phys. Rev. B 87, 161302 (2013)] and support the possibility to control a spin qubit by means of gtensor modulation.
 
2.  Cotunneling in the ν= 5/2 fractional quantum Hall regime 
Robert Zielke, Bernd Braunecker, and Daniel Loss. Phys. Rev. B 86, 235307 (2012); arXiv:1204.4400.
We show that cotunneling in the 5/2 fractional quantum Hall regime allows us
to test the MooreRead wave function, proposed for this regime, and to probe
the nature of the fractional charge carriers. We calculate the cotunneling
current for electrons that tunnel between two quantum Hall edge states via a
quantum dot and for quasiparticles with fractional charges e/4 and e/2 that
tunnel via an antidot. While electron cotunneling is strongly suppressed, the
quasiparticle tunneling shows signatures characteristic of the MooreRead
state. For comparison, we also consider cotunneling between Laughlin states,
and find that electron transport between MooreRead states and between Laughlin
states at filling factor 1/3 have identical voltage dependences.
