Field-induced suppression of the pi-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB 2 at temperatures near T c - Condensed Matter > SuperconductivityReport as inadecuate




Field-induced suppression of the pi-band superconductivity and magnetic hysteresis in the microwave surface resistance of MgB 2 at temperatures near T c - Condensed Matter > Superconductivity - Download this document for free, or read online. Document in PDF available to download.

Abstract: We report on the magnetic-field-induced variations of the microwave surfaceresistance, R s, in a polycrystalline MgB 2 sample, at different values oftemperature. We have detected a magnetic hysteresis in R s, which exhibits anunexpected plateau on decreasing the DC magnetic field below a certain value.In particular, at temperatures near T c the hysteresis manifests itself onlythrough the presence of the plateau. Although we do not quantitatively justifythe anomalous shape of the magnetic hysteresis, we show that the resultsobtained in the reversible region of the R sH curve can be quite wellaccounted for by supposing that, in this range of magnetic field, the pi-gap isalmost suppressed by the applied field and, consequently, all the pi-bandcharge carriers are quasiparticles. On this hypothesis, we have calculatedR sH supposing that fluxons assume a conventional single core structure andthe flux dynamics can be described in the framework of conventional models.From the fitting of the experimental results, we determine the values ofH {c2}^piT at temperatures near T c. In our opinion, the most importantresult of our investigation is that, at least at temperatures near T c, thevalue of the applied field that separates the reversible and irreversibleregions of the R sH curves is just H {c2}^piT; a qualitative discussion ofthe possible reason of this finding is given.



Author: M. Bonura, A. Agliolo Gallitto, M. Li Vigni, G. A. Ummarino

Source: https://arxiv.org/



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