Critical current density and vortex phase diagram in the superconductor Sn0.55In0.45Te

Abstract

Critical current density and vortex pinning dynamics have been studied in the superconductor ${\mathrm{Sn}}_{0.55}{\mathrm{In}}_{0.45}\mathrm{Te}$. Analysis of the temperature-dependent lower critical field shows that it has a weakly anisotropic single energy gap. The critical current density ${J}_{c}(0)$ and pinning potential ${U}_{0}(H)$ values reach as high as $2.56\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{0.16em}{0ex}}\mathrm{A}/{\mathrm{cm}}^{2}$ at 1.8 K and $2.1\ifmmode\times\else\texttimes\fi{}{10}^{3}$ K at ${\ensuremath{\mu}}_{0}H=0.01\phantom{\rule{3.33333pt}{0ex}}\mathrm{T}$, respectively. Based on the collective pinning model, we demonstrate the coexistence of vortex pinning regimes in ${\mathrm{Sn}}_{0.55}{\mathrm{In}}_{0.45}\mathrm{Te}$. One is a $\ensuremath{\delta}{T}_{\mathrm{c}}$ pinning regime induced by the spatial fluctuations of the transition temperature in a low field. The other is a dominantly $\ensuremath{\delta}l$ pinning regime associated with the spatial variations of the charge-carrier mean free path in a higher field. This causes a nonconstant exponent of the power-law behavior ${J}_{c}(T)\ensuremath{\propto}{H}^{n}$. A very weak vortex fluctuation is unveiled by a narrow separation between the irreversibility field ${\ensuremath{\mu}}_{0}{H}_{\mathrm{irr}}(T)$ and upper critical field ${\ensuremath{\mu}}_{0}{H}_{\mathrm{c}2}(T)$ in the vortex phase diagram. We discuss the potential application in superconducting electronics like the single-photon detector in thin film form.