Unexpected superconductivity at nanoscale junctions made on the topological crystalline insulator Pb0.6Sn0.4Te

Abstract

Discovery of exotic phases of matter from the topologically non-trivial systems not only makes the research on topological materials more interesting but also enriches our understanding of the fascinating physics of such materials. Pb 0.6 Sn 0.4 Te was recently shown to be a topological crystalline insulator. Here we show that by forming a mesoscopic point-contact using a normal nonsuperconducting elemental metal on the surface of Pb 0.6 Sn 0.4 Te a novel superconducting phase is created locally in a confined region under the point-contact. This happens while the bulk of the sample remains to be non-superconducting and the superconducting phase emerges as a nanodroplet under the point-contact. The superconducting phase shows a high transition temperature T c that varies for different point-contacts and falls in a range between 3.7 K and 6.5 K. Therefore, this Letter presents the discovery of a new superconducting phase on the surface of a topological crystalline insulator and the discovery is expected to shed light on the mechanism of induced superconductivity in topologically non-trivial systems in general.

Coexistence of type-I and type-II superconductivity in topological superconductor PdTe$_2$

“…For example, it has been argued that TSC can be induced by designing proximity-coupled heterostructures in topological surface states by interfacing with conventional superconductors [16][17][18], and by applying pressure on topological systems [19]. Likewise, superconductivity emerges in a confined dimension by forming a mesoscopic point con-tact between the pure element and topological materials [20][21][22]. All these methods work towards a common goal to realize an ideal system in which topology and superconductivity can be studied unambiguously.…”

Mesoscopic superconductivity and high spin polarization coexisting at metallic point contacts on Weyl semimetal TaAs

“…Therefore, the point contact spectra presented above hint to the possible existence of a tipinduced superconducting (TISC) phase on TaAs -similar to what was observed on the 3D Dirac semimetal Cd 3 As 2 [25,30] and the topological crystalline insulator Pb 0.6 Sn 0.4 Te. [26] In order to further confirm the existence of a TISC, we have measured the temperature dependence of the point contact resistance (Figure 1(e)) corresponding to the spectrum presented in Figure 1(b). A resistive transition, similar to a superconducting transition, is clearly seen at 7K.…”

“…Such experiments can reveal mesoscopic superconducting phases like a TISC that emerge only under point contacts on exotic materials. [25,26] Furthermore, by driving the point contacts to the ballistic regime of transport, it is also possible to extract spectroscopic information of the superconducting phase. [27] In Figure 1 (a) we show the schematic of point contacts made on single crystals of TaAs.…”

Chiral $p-$wave superconductivity in Pb$_{1-x}$Sn$_{x}$Te: signatures from bound-state spectra and wavefunctions

“…On the experimental front, recent point-contact spectroscopy measurements have confirmed the existence of superconductivity of the (001) surface of this system, but the nature of the superconducting order is yet to be ascertained. The superconductivity is indicated by a sharp fall in the resistance of the point contact below a characteristic temperature (3.7-6.5 K) 31 and the appearance of a spectral gap with coherence peak-like features, and zero-bias anomalies. 31,32 However, contrary to the claim in Ref.…”

“…The superconductivity is indicated by a sharp fall in the resistance of the point contact below a characteristic temperature (3.7-6.5 K) 31 and the appearance of a spectral gap with coherence peak-like features, and zero-bias anomalies. 31,32 However, contrary to the claim in Ref. 32, these zero-bias peaks are not necessarily signatures of Majorana bound states.…”