Heavy Fermion Materials
A prominent class of strongly correlated electron systems is heavy-fermion materials. The softness, i.e. “responsiveness”, of these materials to external control parameters makes them a prototype model setting for investigating the type of quantum phases and fluctuations that are created by strong correlations, which is the key question in correlated electron materials in particular and quantum systems in general.
Our focus has been/is in several systems, including the members of the homologous series CemTnIn3m+2n, where m = 1, 2; n = 0, 1; T = Co, Rh, Ir and doped derivatives thereof. We investigated the crystal structure of all members of the series by using, in addition to conventional X-ray diffraction and electron diffraction/microscopy, single crystal and powder neutron and synchrotron X-ray diffraction (including reciprocal space mapping) and combinations thereof. Our aim was/is to accurately probe the structure of the various phases at various sample environments, but more importantly to define the structural signatures associated with the magnetic or superconducting transitions that these systems undergo as a function of a control parameter. The key tuning parameters to unravel the behavior of these systems are temperature, pressure, magnetic field, structural disorder, dimensionality and strain. Examples of this area of research are shown below.
Synchrotron X-ray Reciprocal Space Maps (i) and the corresponding peak profiles (ii) of the (023) reflection at: (a) room temperature and (b) 10 K.