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) comments original reference
CeCu2Si2 0.7 first unconventional superconductor [1]
CeCoIn5 2.3 highest TC of all Ce-based heavy fermions [2]
CeIn3 0.2 superconducting only at high pressures [3]
UPt3 0.48 several distinct superconducting phases [4]
URu2Si2 1.3 mysterious 'hidden-order phase' below 17 K
UPd2Al3 2.0 antiferromagnetic below 14 K [5]
UNi2Al3 1.1 antiferromagnetic below 5 K [6]

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.[7] In contrast to normal superconductors it cannot be described by BCS-Theory. Due to the large effective mass,[8] 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.[9] In particular there has been evidence that CeCoIn5 close to the critical field is in an FFLO state.[10]

References[edit]

  1. ^ a b 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. 
  2. ^ a b 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/0103168free to read. Bibcode:2001JPCM...13L.337P. doi:10.1088/0953-8984/13/17/103. 
  3. ^ Mathur, N.D.; Grosche, F.M.; Julian, S.R.; Walker, I.R.; Freye, D.M.; Haselwimmer, R.K.W.; Lonzarich, G.G. (1998). "Magnetically mediated superconductivity in heavy fermion compounds". Nature. 394: 39. doi:10.1038/27838. 
  4. ^ Stewart, G.R.; Fisk, Z.; Willis, J.O.; Smith, J.L. (1984). "Possibility of Coexistence of Bulk Superconductivity and Spin Fluctuations in UPt3". Phys. Rev. Lett. 52: 679. doi:10.1103/PhysRevLett.52.679. 
  5. ^ Geibel, C.; Schank, C.; Thies, S.; Kitazawa, H.; Bredl, C.D.; Böhm, A.; Rau, M.; Grauel, A.; Caspary, R.; Helfrich, R.; Ahlheim, U.; Weber, G.; Steglich, F. (1991). "Heavy-fermion superconductivity at Tc=2K in the antiferromagnet UPd2Al3". Z. Phys. B. 84: 1. doi:10.1007/BF01453750. 
  6. ^ Geibel, C.; Thies, S.; Kaczorowski, D.; Mehner, A.; Grauel, A.; Seidel, B.; Ahlheim, U.; Helfrich, R.; Petersen, K.; Bredl, C.D.; Steglich, F. (1991). "A new heavy-fermion superconductor: UNi2Al3". Z. Phys. B. 83: 305. doi:10.1007/BF01313397. 
  7. ^ Neil W. Ashcroft and N. David Mermin, Solid State Physics
  8. ^ Pfleiderer, C. (2009). "Superconducting phases of f -electron compounds". Reviews of Modern Physics. 81: 1551–1624. arXiv:0905.2625free to read. Bibcode:2009RvMP...81.1551P. doi:10.1103/RevModPhys.81.1551. 
  9. ^ Matsuda, Yuji; Shimahara, Hiroshi (2007). "Fulde-Ferrell-Larkin-Ovchinnikov State in Heavy Fermion Superconductors". J. Phys. Soc. Jpn. 76: 051005. arXiv:cond-mat/0702481free to read. Bibcode:2007JPSJ...76e1005M. doi:10.1143/JPSJ.76.051005. 
  10. ^ 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/0304420free to read. Bibcode:2003PhRvL..91r7004B. doi:10.1103/PhysRevLett.91.187004.