What decides whether disorder destroys pairing or only phase coherence? · revision history
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Accepted · first revision · record
- Title
- What decides whether disorder destroys pairing or only phase coherence?
- Plain
- Disorder can end superconductivity in two ways: by breaking the electron pairs, or by leaving the pairs intact but stopping them from moving together in step. Some films, such as amorphous indium oxide and titanium nitride, keep a pairing gap into the insulator, while in others the gap seems to close together with the transition temperature, and what selects the route is not known.
- Precise
- Near the disorder-tuned 2D superconductor-insulator transition, the fermionic route (Coulomb-enhanced suppression of the pairing amplitude, Finkel'stein) has the gap $\Delta\to 0$ together with $T_c$, while the bosonic route keeps a finite $\Delta$ and a pseudogap above $T_c$, with $T_c\to 0$ from phase fluctuations or localization of preformed pairs (Sacepe et al., Nature Physics 2011, in InOx). Identify the material parameter that selects the route (for example $k_F\ell$, the ratio of Coulomb to pairing strength, or the Debye energy relative to the level spacing in a localization volume) and give a criterion that predicts the route for a given film.
- Settled by
- Tunneling measurements of $\Delta(T)$ and $T_c$ across disorder series in several material families, matched to a theory whose criterion predicts each family's route in advance.
- Kind
- well-posed
- Answer type
- classification
- References
- (empty)
- Literature status
- open
- Status note
- A 2020 review describes both routes and granular behavior without a predictive criterion (Sacepe, Feigel'man and Klapwijk, Nature Physics 16, 734, 2020); a first-order disorder-driven transition was reported in InOx in 2025 (Charpentier et al., Nature Physics 21, 104).
- Posed since
- (empty)