Abstract
The quantum breakdown of superconductivity (QBS) is the reverse, comprehensive approach to the appearance of superconductivity. A quantum phase transition from superconducting to insulating states tuned by using nonthermal parameters is of fundamental importance to understanding the superconducting (SC) phase but also to practical applications of SC materials. However, the mechanism of the transition to a nonzero resistive state deep in the SC state is still under debate. Here, we report a systematic study of MgB2 bilayers with different thickness ratios for undamaged and damaged layers fabricated by low-energy iron-ion irradiation. The field-induced QBS is discovered at a critical field of 3.2 Tesla (=Hc), where the quantum percolation model best explains the scaling of the magnetoresistance near Hc. As the thickness of the undamaged layer is increased, strikingly, superconductivity is recovered from the insulating state associated with the QBS, showing that destruction of quantum phase coherence among Cooper electron pairs is the origin of the QBS.
Highlights
Disorder in materials is undesirable because it prevents investigations of the intrinsic properties of the material
We report magnetic-field-induced quantum breakdown of superconductivity in MgB2 thin films via irradiation with 140-keV Fe-ion beams
Because elastic scattering of the incident ions by nuclei in the materials is dominant for low-energy ion irradiation, lattice displacements, together with the formation of vacancies and interstitials, take place in the irradiated crystal, leading to changes in SC critical properties[15,16,17]
Summary
Disorder in materials is undesirable because it prevents investigations of the intrinsic properties of the material. Disorder can be useful in manipulating superconducting properties. Breaks the coherence of SC electron pairs and gives rise to a change from the SC ground state to an insulating or non-SC metallic state at the quantum breakdown of superconductivity (QBS)[3,4,5,6,7,8,9,10,11,12,13,14]. As disorder increases, superconducting islands may appear in the destroyed background of non-SC regions owing to inhomogeneous suppression of superconductivity[3,4,5,6,11].
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