High-temperature superconductivity in topological insulators

Interest in the superconducting proximity effect has been reinvigorated recently by novel optoelectronic applications as well as by the possible emergence of the elusive Majorana fermion. However, all previously studied structures were based on low-T$_{\mathrm{c}}$ materials. We have produced high-temperature superconductivity in topological insulators Bi$_2$Se$_3$ and Bi$_2$Te$_3$ via proximity to Bi$_2$Sr$_2$CaCu$_2$O$_{\mathrm{8+\delta}}$, using our new mechanical bonding technique. We have shown proximity-induced superconductivity up to a temperature of at least 80K -- an order of magnitude higher than any previous observations. We have also demonstrated hybrid high-Tc-superconductor-semiconductor tunnel junctions combining Bi$_2$Sr$_2$CaCu$_2$O$_{\mathrm{8+\delta}}$ with graphite, with bulk semiconductors and with semiconductor quantum wells. Our approach provides a simple method of constructing high-T$_{\mathrm{c}}$ tunnel junctions which can conceptually facilitate tunneling spectroscopy studies of novel materials.