Heavy fermion superconductor
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Heavy fermion superconductors are a type of unconventional superconductor.
The first heavy fermion superconductor, CeCu2Si2, was discovered by Frank Steglich in 1978.[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]
| Material | TC (K) |
|---|---|
| CeCu2Si2 | 0.7 |
| CeCoIn5 | 2.3 |
| CeIn3 | 0.2 |
| UPt3 | 0.48 |
| URu2Si2 | 1.3 |
| UPd2Al3 | 2.0 |
| UNi2Al3 | 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.[citation needed]
From specific heat measurements (ΔC/C(TC) one knows that the Cooper pairs in the superconducting state are also formed by the heavy quasiparticles.[3] In contrast to normal superconductors it cannot be described by BCS-Theory. Due to the large effective mass,[4] 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.[citation needed]
Some heavy fermion superconductors are candidate materials for the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase.[5] In particular there has been evidence that CeCoIn5 close to the critical field is in an FFLO state.[6]
References
- ^ Steglich, F.; Aarts, J.; Bredl, C.D.; Lieke, W.; Meschede, D.; Franz, W.; Schäfer, H. (1979). "Superconductivity in the Presence of Strong Pauli Paramagnetism: CeCu2Si2". Physical Review Letters. 43: 1892–1896. Bibcode:1979PhRvL..43.1892S. doi:10.1103/PhysRevLett.43.1892.
- ^ Petrovic, C.; Pagliuso, P.G.; Hundley, M.F.; Movshovich, R.; Sarrao, J.L.; Thompson, J.D.; Fisk, Z.; Monthoux, P. (2001). "Heavy-fermion superconductivity in CeCoIn5 at 2.3 K". Journal of Physics: Condensed Matter. 13: L337. arXiv:cond-mat/0103168. Bibcode:2001JPCM...13L.337P. doi:10.1088/0953-8984/13/17/103.
- ^ Neil W. Ashcroft and N. David Mermin, Solid State Physics
- ^ Pfleiderer, C. (2009). "Superconducting phases of f -electron compounds". Reviews of Modern Physics. 81: 1551–1624. arXiv:0905.2625. Bibcode:2009RvMP...81.1551P. doi:10.1103/RevModPhys.81.1551.
- ^ Matsuda, Yuji; Shimahara, Hiroshi (2007). "Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors". J. Phys. Soc. Jpn. 76: 051005. arXiv:cond-mat/0702481. Bibcode:2007JPSJ...76e1005M. doi:10.1143/JPSJ.76.051005.
- ^ Bianchi, A.; Movshovich, R.; Capan, C.; Pagliuso, P.G.; Sarrao, J.L. (2003). "Possible Fulde-Ferrell-Larkin-Ovchinnikov State in CeCoIn5". Phys. Rev. Lett. 91: 187004. arXiv:cond-mat/0304420. Bibcode:2003PhRvL..91r7004B. doi:10.1103/PhysRevLett.91.187004.