High Field Magnetic White Dwarfs vs. phosphorus in silicon: spectroscopy of hydrogenic orbitals under extreme field conditions

When?

Thursday 29 March 2012, 13:00

Where?

02ATI02

Open to:

Staff, Students

Speaker:

Professor Ben Murdin, Advanced Technology Institute, University of Surrey

In astronomy, although it sounds oxymoronic, “extreme” environments are commonplace.  Here I mean conditions difficult or impossible to reproduce terrestrially, and good examples of this are the very high magnetic fields that are by now well known to exist on the surfaces of white dwarfs and neutron stars, way beyond the few tens of tesla that can be produced in the laboratory. I will describe a measurement of hydrogenic states produced by phosophorus impurities in silicon, under the same conditions that are experienced on the surface of the highest field white dwarf known, equivalent to 100,000T.  

Under these extreme conditions, there are major changes in well known physics effects.  Nearly everyone who has ever studied magnetic resonance, a technique pervasive across all the sciences and engineering, has been taught that the Zeeman splitting is linear with the applied field.  At high field it becomes quadratic, but the conditions under which this is relevant have been limited mainly to the astronomical situations mentioned above.  I shall show that strongly quadratic Zeeman splittings are now relatively easy to obtain using laboratory high field facilities.