Thursday, January 24, 2013

PhD position available: A carbon nanotube as a moving weak link

The combination of localized states within carbon nanotubes and superconducting contact materials leads to a manifold of fascinating physical phenomena and is a very active area of current research. An additional bonus is that the carbon nanotube can be suspended, i.e. the quantum dot between the contacts forms a nanomechanical system. In this research field a PhD position is immediately available; the working title of the project is "A carbon nanotube as a moving weak link".

You will develop and fabricate chip structures combining various superconductor contact materials with ultra-clean, as-grown carbon nanotubes. Together with your colleagues, you will optimize material, chip geometry, nanotube growth process, and measurement electronics. Measurements will take place in one of our ultra-low temperature setups.

Good knowledge of superconductivity is required. Certainly helpful is knowledge of semiconductor nanostructures and low temperature physics, as well as basic familiarity with Linux. The starting salary is 1/2 TV-L E13.

Interested? Contact Andreas K. Hüttel (e-mail:, web: ) for more information!

PhD position available: Gigahertz nanomechanics with carbon nanotubes

We are currently working on integrating carbon nanotube nanomechanical systems into superconducting radio-frequency electronics. Overall objective is the detection and control of nanomechanical motion towards its quantum limit. In this project, we've got a PhD position with project working title "Gigahertz nanomechanics with carbon nanotubes" available immediately.

You will design and fabricate superconducting on-chip structures suitable as both carbon nanotube contact electrodes and gigahertz circuit elements. In addition, you will build up and use - together with your colleagues - two ultra-low temperature measurement setups to conduct cutting-edge measurements.

Good knowledge of electrodynamics and possibly superconductivity are required. Certainly helpful is low temperature physics, some sort of programming experience, as well as basic familiarity with Linux. The starting salary is 1/2 TV-L E13.

Interested? Contact Andreas K. Hüttel (e-mail:, web: ) for more information!

Tuesday, January 1, 2013

JAP accepted: Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips

Right at the start the new year 2013 brings the pleasant news that our manuscript "Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips" has found its way into Journal of Applied Physics. The background of this work is - once again - spin injection and spin-dependent transport in carbon nanotubes. (To be more precise, the manuscript resulted from our ongoing SFB 689 project.) Control of the contact magnetization is the first step for all the experiments. Some time ago we picked Pd0.3Ni0.7 as contact material since the palladium generates only a low resistance between nanotube and its leads. The behaviour of the contact strips fabricated from this alloy turned out to be rather complex, though, and this manuscript summarizes our results on their magnetic properties.
Three methods are used to obtain data - SQUID magnetization measurements of a large ensemble of lithographically identical strips, anisotropic magnetoresistance measurements of single strips, and magnetic force microscopy of the resulting domain pattern. All measurements are consistent with the rather non-intuitive result that the magnetically easy axis is perpendicular to the geometrically long strip axis. We can explain this by maneto-elastic coupling, i.e., stress imprinted during fabrication of the strips leads to preferential alignment of the magnetic moments orthogonal to the strip direction.

"Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips"
D. Steininger, A. K. Hüttel, M. Ziola, M. Kiessling, M. Sperl, G. Bayreuther, and Ch. Strunk
Journal of Applied Physics 113, 034303 (2013); arXiv:1208.2163 (PDF[*])
[*] Copyright American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.