The Theory Study Of Surface Bound States In Fe-pnictide Superconductors

Fe-pnictide superconductor is an innormal second superconductor with high Tc (56K).It has multiple characteristics of high Tc copper-oxide superconductor，but the cristal andelectron structure are different. The key problem of Fe-pnictide superconductor is toensure its pairing symmetry. Different Fe-pnictide superconductor materials has shownthat the similar characteristics of superconductor, the same samples of Fe-pnictidesuperconducting is measured in different experiments with different symmetry, even thesame sample in the same experiments have different results by different classes. Thetranditional theory can’t explain these experiments result, how to explain theseexperiments result by theory frame, which is the goal of this paper. Our study used thetheory of Blonder-Tinkham-Klapwijk(BTK) to solve the surface bound states of thesuperconductor, on the base of appreciating zero-energy surface bound states are shown itexist in Fe-pnictide superconductor with s~±-wave pairing. The clued about this paper isfollow:Firstly, we introduced the basics theory of the superconductor: copper pair、the pairpotential of the different superconductors、Resonating Valence Bounds (RVB)theory andBogoliubov-deGennes(BdG) equation，and introduced the Andreev reflection and thetheory of BTK.Secondly, we introduced the bound states of the superconductor, and used the theoryof BTK and BdG equations solving the Andreev equation, then came to the condition ofzero-energy surface bound states exsisting of the d-wave superconductor.Finally, we compared the experiment date to the above theory formular we had taking,and explained the why we observed different zero-bias conductance peaks in the deferentexperiment. We discussed the different zero-energy surface bound states existing ins~±-wave pairing Fe-pnictide superconductor with different N FSinterfae orientationand discussed the relationship between the orientation and zero-energy surface boundstates form three cases, giving the best fitting of the theory and the measurement.