Microscopic origin of density-of-states reduction in irradiated YBCO weak links

Identify the microscopic mechanism responsible for the reduction in the local effective density of states in helium-ion-irradiated YBCO weak links.

Background

The paper interprets the exponential increase in the normal-state resistance and the suppression of the characteristic voltage in terms of a decreasing effective density of states within the helium-ion-irradiated weak-link region. This interpretation follows from an Einstein-relation analysis in which the extracted Thouless energy varies only weakly with irradiation dose, while the normal-state resistance increases strongly.

The authors suggest that a pseudogap-like suppression of the density of states induced by nanoscale disorder could account for the observations, but they explicitly state that the microscopic mechanism producing this reduction has not been conclusively identified. Determining that mechanism remains an unresolved issue for understanding the electronic structure and transport of irradiated YBCO weak links.

References

Although the microscopic mechanism responsible for such a reduction in the local effective density of states in YBCO weak links cannot be identified conclusively at present, the observed behavior is consistent with the suppression of the density of states associated with the pseudogap phase universaly observed in underdoped cuprate high-temperature superconductors, including YBCO.

— Josephson transport in YBa${}_{2}$Cu${}_{3}$O${}_{7}$ weak links created by focused-helium-ion-beam irradiation: Analysis based on diffusive-SNS-junction model  (2608.20109 - Misawa et al., 20 Aug 2026) in Section “Phenomenological description of the YBCO weak links”