What Is The Effect Of Ce3+ Ion Substitution On The Fermi Surface Topology And Superconducting Gap Symmetry In A CeCoIn5 Single Crystal, When Subjected To A Uniaxial Pressure Of 1 GPa Along The C-axis, And How Does This Influence The Emergence Of A Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) State At Low Temperatures?

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The effect of Ce³+ ion substitution and uniaxial pressure on CeCoIn5 can be understood through their impact on the electronic structure, Fermi surface topology, and superconducting gap symmetry, which collectively influence the emergence of the FFLO state. Here's a structured summary:

  1. Ce³+ Substitution:

    • Substituting Ce³+ ions with other rare-earth ions alters the electronic structure by changing lattice constants, electron interactions, and the density of states. This affects the hybridization between conduction and f-electrons, potentially modifying the Fermi surface and superconducting gap symmetry.

  2. Uniaxial Pressure Along the c-axis:

    • Applying pressure along the c-axis modifies the crystal structure, likely making the system more two-dimensional. This changes the electronic band structure, altering the Fermi surface's shape and possibly its nesting properties.

  3. Fermi Surface Topology and Superconducting Gap Symmetry:

    • Changes in Fermi surface topology due to substitution and pressure can affect the pairing symmetry. A more cylindrical Fermi surface might favor line nodes in the superconducting gap, potentially altering from d-wave to a different symmetry.

  4. Emergence of the FFLO State:

    • The FFLO state is favored under conditions that allow spatial modulation of the superconducting order parameter. Substitution and pressure tune the electronic structure, potentially creating conditions conducive to FFLO, especially if the modified Fermi surface and gap symmetry support the necessary pairing conditions.

In conclusion, Ce³+ substitution and uniaxial pressure along the c-axis modify CeCoIn5's electronic structure, influencing Fermi surface topology and gap symmetry. These changes create conditions favorable for the FFLO state to emerge at low temperatures, particularly if the modified electronic properties support the required pairing conditions.