Effects of disorder on superconductivity of systems with coexisting itinerant electrons and local pairs

G. Pawłowski; R. Micnas; S. Robaszkiewicz

doi:10.1103/PhysRevB.81.064514

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Effects of disorder on superconductivity of systems with coexisting itinerant electrons and local pairs

G. Pawłowski, R. Micnas, S. Robaszkiewicz

DOI 10.1103/PhysRevB.81.064514 · Physical Review B

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Abstract

We study the influence of diagonal disorder (random site energy) of local pair (LP) site energies on the superconducting properties of a system of coexisting local pairs and itinerant electrons described by the (hardcore) boson-fermion model. Our analysis shows that the properties of such a model with s-wave pairing can be very strongly affected by the diagonal disorder in LP subsystem (the randomness of the LP site energies). This is in contrast with the conventional s-wave BCS superconductors, which according to the Anderson’s theorem are rather insensitive to the diagonal disorder (i.e., to nonmagnetic impurities). It has been found that the disorder effects depend in a crucial way on the total particle concentration n and the LP level position Δo and depending on the parameters the system can exhibit various types of superconducting behavior, including the LP-like, intermediate (MIXED), and the “BCS”-like. In the extended range of {n,Δo} the superconducting ordering is suppressed by the randomness of the LP site energies and the increasing disorder induces a changeover from the MIXED-like behavior to the BCS-like one, connected with abrupt reduction in Tc and energy gap to zero. However, there also exists a definite range of {n,Δo} in which the increasing disorder has a quite different effect: namely, it can substantially enhance Tc or even lead to the phenomenon which can be called disorder-induced superconductivity. Another interesting effect is a possibility of a disorder-induced bound pair formation of itinerant electrons, connected with the changeover to the LP-like regime.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
BaBixPb1-xO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ba1-xKxBiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Pb1-xTlxTe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Pb1-xSnxSe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Cs2SbCl3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
CsAgCl3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ti4O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ti4-xVxO7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
WO3-x Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
PbHx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Li1-xTi2-xO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
EuxMo6S8 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
NbC Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
BaBiO3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown