[1] Since then over 30 heavy fermion superconductors were found (in materials based on Ce, U), with a critical temperature up to 2.3 K (in CeCoIn5).
[2] Heavy fermion materials are intermetallic compounds, containing rare earth or actinide elements.
The f-electrons of these atoms hybridize with the normal conduction electrons leading to quasiparticles with an enhanced effective mass.
Due to the large effective mass,[11] the Fermi velocity is reduced and comparable to the inverse Debye frequency.
[citation needed] Some heavy fermion superconductors are candidate materials for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase.