Experimental aspects of the specific heat of superconductors derived from topological insulators

The expectation for topological superconductors to have an unconventional pairing symmetry makes them promising hosts for Majorana fermions. Recently the topological insulators Bi₂Se₃ (BS) and (PbSe)₅(Bi₂Se₃)₆ (PSBS) were reported to become superconducting when intercalating them with copper. Literature data of specific heat on both, Cu_xBS and Cu_xPSBS, indicate an unusual temperature dependence not described by standard BCS theory. This makes them promising candidates of topological superconductors but in order to clarify these issues it is necessary to perform c_p measurements below 250 mK using a ³He/⁴He dilution cryostat. Because c_p of superconductors becomes very small far below T_c the addendum contribution of the setup has to be minimized. This demand together with other complications e.g. nuclear Schottky contributions to c_p, leads to a drastic increase of the experimental effort. In this contribution experimental aspects of c_p measurements with respect to the topological superconductor materials will be discussed in detail.