Heavy fermion superconductor
Encyclopedia
Heavy fermion superconductors are a type of Unconventional superconductor.
The first heavy fermion
superconductor, CeCu2Si2, was discovered by Frank Steglich
in 1978.
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).
Heavy Fermions 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 mass.
From specific heat measurements (ΔC/C(TC) one knows that the Cooper pair
s in the superconducting state are also formed by the heavy quasiparticles.
In contrast to normal superconductors it cannot be described by BCS-Theory. Due to the large effective mass, the
Fermi velocity is reduced and comparable to the inverse Debye frequency. This leads to the failing of the picture of electrons polarizing the lattice as an attractive force.
Some heavy fermion superconductors are candidate materials for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase
. In particular there has been evidence that CeCoIn5 close to the critical field is in an FFLO state.
The first heavy fermion
Heavy Fermion
In solid-state physics, heavy fermion materials are a specific type of intermetallic compound, containing elements with 4f or 5f electrons. Electrons, a kind of fermion, found in such materials are sometimes referred to as heavy electrons...
superconductor, CeCu2Si2, was discovered by Frank Steglich
Frank Steglich
Frank Steglich is a German physicist.He received the Gottfried Wilhelm Leibniz Prize by the Deutsche Forschungsgemeinschaft in 1986 and a number of other recognitions...
in 1978.
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).
| Material | TC (K) |
|---|---|
| CeCu2Si2 | 0.7 |
| CeCoIn5 | 2.3 |
| CeIn3 | 0.2 |
| UPt3 | 0.48 |
| URu2Si2 | 1.3 |
| UPd2Al3 | 2.0 |
| UPd2Al3 | 1.1 |
Heavy Fermions 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 mass.
From specific heat measurements (ΔC/C(TC) one knows that the Cooper pair
Cooper pair
In condensed matter physics, a Cooper pair or BCS pair is two electrons that are bound together at low temperatures in a certain manner first described in 1956 by American physicist Leon Cooper...
s in the superconducting state are also formed by the heavy quasiparticles.
In contrast to normal superconductors it cannot be described by BCS-Theory. Due to the large effective mass, the
Fermi velocity is reduced and comparable to the inverse Debye frequency. This leads to the failing of the picture of electrons polarizing the lattice as an attractive force.
Some heavy fermion superconductors are candidate materials for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase
Fulde-Ferrell-Larkin-Ovchinnikov phase
The Fulde-Ferrell-Larkin-Ovchinnikov phase can arise in a superconductor in large magnetic field. Among its characteristics are Cooper pairs with nonzero total momentum and a spatially non-uniform order parameter.- History :...
. In particular there has been evidence that CeCoIn5 close to the critical field is in an FFLO state.