New bi-epitaxial Grain boundary Josephson Junction of FeSe$_{0.3}$Te$_{0.7}$

We have successfully fabricated epitaxial FeSe$_{0.3}$Te$_{0.7}$films on MgO substrate with its in-plane crystalline axis either parallel to or rotated 45$^{\circ}$ with respect to the MgO lattice. We use this technique to fabricate the 45$^{\circ}$ grain-boundary Josephson junction. The IV-curve measured at 4.2 K can be fitted with the RSJ model, and the measured I$_{c}$R$_{n}$value is 9.24$\mu$V, which is in general agreement with the values obtained by previous results for Fe-based grainboundary junctions on bi-crystal substrates. We have also measured the dc Josephson current as a function of applied magnetic fields, which shows a clear Fraunhofer-like pattern. Hence we can rule out the possibility of d-wave symmetry in FeSe$_{0.3}$Te$_{0.7}$ superconductor. Upon applying 6 GHz microwave irradiation, the junction IV curve exhibits clear Shapiro steps. Thus we have demonstrated our ability to fabricate high quality grain-boundary Josephson junctions of this new class of material. Further physical properties, such as the noise power spectrum, are currently being investigated.