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We study one-dimensional chains of superconducting islands with a particular emphasis on the regime in which every second island is switched into its normal state, thus forming a superconductor-insulator-normal metal (S-I-N) repetition pattern. As is known since Giaever tunneling experiments, tunneling charge transport between a superconductor and a normal metal becomes exponentially suppressed, and zero-bias resistance diverges, as the temperature is reduced and the energy gap of the superconductor grows larger than the thermal energy. Here we demonstrate that this physical phenomenon strongly impacts transport properties of inhomogeneous superconductors made of weakly coupled islands with fluctuating values of the critical temperature. We observe a nonmonotonous dependence of the chain resistance on both temperature and magnetic field, with a pronounced resistance peak at temperatures at which some but not all islands are superconducting. We explain this phenomenon by the inhomogeneity of the chains, in which neighboring superconducting islands have slightly different critical temperatures. We argue that the Giaever’s resistance divergence can also occur in the zero-temperature limit. Such quantum transition can occur if the magnetic field is tuned such that it suppresses superconductivity in the islands with the weaker critical field, while the islands with stronger energy gap remain superconducting. In such a field, the system acts as a chain of S-I-N junctions.
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This content will become publicly available on January 7, 2026
Evidence for a metal–bosonic insulator–superconductor transition in compressed sulfur
The abrupt drop of resistance to zero at a critical temperature is a key signature of the current paradigm of the metal–superconductor transition. However, the emergence of an intermediate bosonic insulating state characterized by a resistance peak preceding the onset of the superconducting transition has challenged this traditional understanding. Notably, this phenomenon has been predominantly observed in disordered or chemically doped low-dimensional systems, raising intriguing questions about the generality of the effect and its underlying fundamental physics. Here, we present a systematic experimental study of compressed elemental sulfur, an undoped three-dimensional (3D) high-pressure superconductor, with detailed measurements of electrical resistance as a function of temperature, magnetic field, and current. The anomalous resistance peak observed in this 3D system is interpreted based on an empirical model of a metal–bosonic insulator–superconductor transition, potentially driven by vortex dynamics under magnetic field and energy dissipation processes. These findings offer a fresh platform for theoretical analysis of the decades-long enigmatic of the underlying mechanism of this phenomenon.
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- Award ID(s):
- 2104881
- PAR ID:
- 10582587
- Publisher / Repository:
- PNAS
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 122
- Issue:
- 1
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- e2420904122
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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