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Rob KieflMy research interests are in
condensed matter physics and in particular the area of so called quantum
materials and their interfaces. In general the properties of an
interface (or surface region) are different that the properties of the two
constituent materials in the same way a molecule has different properties
than its constituent atoms. Our goals are to discover exactly how these
differences arise near surfaces and interfaces . Our group has been
developing a new technique called low
energy beta- detected NMR, in which a spin polarized beam of
radioactive nuclei produced at the TRIUMF ISAC facility is used a probe
of local magentic and electronic properties of quantum materials
and their interfaces. Much
of condensed matter physics is concerned with the collective state of
electrons in a crystals or solid. Many solids (e.g. semiconductors and
simple metals) can be understood primarily within models where the effective
interactions between electrons can be neglected or treated as a perturbation.
However there are a growing number of materials being discovered with
remarkable properties where the effective interactions are strong and new
theoretical approaches are required. One prominent example is the High Tc
superconductors. Our understanding of such materials is far less
advanced and is guided by an ongoing interplay between experiment and theory.
The low temperature properties of such materials are particularly interesting
since that is where we expect effects due to quantum coherence to be largest.
Materials which exhibit interesting quantum phenomena at low
temperatures (e.g. superconductivity) are called “quantum
materials”. A Heisenberg coupled spin ½ chain is an
example of a quantum magnetic material which is particularly
important since it can be treated precisely from a theory point
of view. One striking quantum effect is that a Heisenberg spin ½ chain has a
gapless excitations spectrum whereas the spin 1 chain has a
Haldane gap [1]. Another example is a geometrically
frustrated Heisenberg antiferromagnet where the dominant near neighbor
interaction is frustrated by the spatial arrangement of the magnetic ions.
This leads to a ground state with a macroscopic degeneracy called
a cooperative paramagnet.
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