Graduate Student Silvia Kusminskiy Models Heavy Fermion Effect

August 07, 2008

Heavy fermions are materials which, at low temperatures, behave like metals with unusually high specific heat and magnetic susceptibility coefficients. These materials can be modeled as a lattice of magnetic impurities embedded in a metallic host. The magnetic interaction between the impurities and the conduction electrons gives rise to new collective entities, called quasi-particles, which behave as very massive electrons.

It is known that an applied magnetic field will eventually destroy the heavy fermion state, however the exact mechanism for this has been debated. In a recent paper published in Physical Review B, graduate student Silvia Viola Kusminskiy and collaborators have proposed a model for the evolution of the Fermi surface of heavy fermion materials in the presence of a magnetic field. Opposite to what is generally argued, they find that the Fermi surface fully polarizes well before the heavy fermion state is destroyed. This manifests itself as a crossover to a phase that they call the “locked state,” which can be confused with the collapse of the heavy fermion state.

Kusminskiy et al. claim that this model can explain the metamagnetic behavior of the heavy fermion compound YbRh2Si2 that has previously been attributed to the aforementioned collapse. Recent experimental results have provided strong evidence for this prediction. You can read more about those results here.