In the tutorials, we see that MgB2 has a well separated superconducting gaps in both delta vs T plot and quasiparticle density of state plot. However, in case of NbSe2 (S. Das et. al. npj Computational Materials (2023) 66) and MoTe2 (Hari Paudyal et. al. PHYSICAL REVIEW B 101, 214515 (2020)) , the papers seem to indicate the presence of multiple gaps although not directly evident from the plots (may be its just me).
Is there any thumb rule or any characteristic features which we need to see in the plots to decide whether a material has single or multiple gaps? Any leads would be of great help.
understanding the superconducting gap vs T plot
Moderator: stiwari
Re: understanding the superconducting gap vs T plot
Hi Ashwath,
In MgB2, the two superconducting gaps are well separated, whereas in MoTe2, the gaps are not as clearly distinct. This difference largely depends on the Fermi surface of the material.
For MgB2, the σ and π bands give rise to two well-separated gaps. In contrast, for MoTe2, the gaps are more closely spaced, although at 0 GPa, you can still observe signatures of a two-gap structure.
You may also want to look at the NaC4 system (Phys. Rev. B 110, 174508), where a two-gap feature is present as well, but the magnitude of the second gap is smaller.
Overall, the presence and separation of multiple gaps depend strongly on the topology of the Fermi surface.
Best,
Shashi
In MgB2, the two superconducting gaps are well separated, whereas in MoTe2, the gaps are not as clearly distinct. This difference largely depends on the Fermi surface of the material.
For MgB2, the σ and π bands give rise to two well-separated gaps. In contrast, for MoTe2, the gaps are more closely spaced, although at 0 GPa, you can still observe signatures of a two-gap structure.
You may also want to look at the NaC4 system (Phys. Rev. B 110, 174508), where a two-gap feature is present as well, but the magnitude of the second gap is smaller.
Overall, the presence and separation of multiple gaps depend strongly on the topology of the Fermi surface.
Best,
Shashi