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

Abstract

The type-II Dirac semimetal PdTe2 was recently reported to be a type-I superconductor with a superconducting transition temperature Tc 1.65 K. However, the recent results from tunneling and point contact spectroscopy suggested the unusual state of a mixture of type-I and type-II superconductivity. These contradictory results mean that there is no clear picture of the superconducting phase diagram and warrants a detailed investigation of the superconducting phase. We report here the muon spin rotation and relaxation (µSR) measurements on the superconducting state of the topological Dirac semimetal PdTe2. From µSR measurements, we find that PdTe2 exhibits mixed type-I/type-II superconductivity. Using these results a phase diagram has been determined. In contrast to previous results where local type-II superconductivity persists up to Hc2 600 G, we observed that bulk superconductivity is destroyed above 225 G.

Electronic and topological properties of group-10 transition metal dichalcogenides

“…These studies have shown the mixed phase of type-I and type-II SC in PdTe 2 [124][125][126]. The critical field (H c ) is observed to vary from 0.0083 to 0.022 T for type-I SC and from 0.025 to 0.32 T for type-II SC [42,86,109,114,118,122,[124][125][126]. Besides, SC in PdTe 2 is quite anistropic [42].…”

“…Various SC parameters for PdTe 2 are shown in table 2. The T c in PdTe 2 is very sensitive to Te stoichiometry and changes from 1.5 to 1.97 K [86,93,109,[112][113][114][115][116][117][118][119][120][121][122][123][124][125][126]. It is observed that 5% Cu intercalation enhances T c up to maximum value of ∼2.6 K [113].…”

“…Although more studies need to be performed on the least studied compounds like NiTe 2 , PdS 2 , PdSe 2 , PtSe 2 and PtTe 2 to confirm the weakly or intermediately coupled BCS mechanism. Several research papers during last five years have appeared in the literature in order to understand the nature and mechanism of SC in PdTe 2 [86,93,109,[112][113][114][115][116][117][118][119][120][121][122][123][124][125][126]. Various SC parameters for PdTe 2 are shown in table 2.…”

“…The STM and STS are surface sensitive techniques. These techniques cannot map different regions of Meissner state, magnetic field distribution and dominant internal field component in the superconducting state [126]. The extraction of magnetic field distribution and mapping of different regions of Meissner state is quintessential to elucidate the commonality and differences of superconducting parameters in a mixed phase type I and type II SC of PdTe 2 [126].…”

“…These techniques cannot map different regions of Meissner state, magnetic field distribution and dominant internal field component in the superconducting state [126]. The extraction of magnetic field distribution and mapping of different regions of Meissner state is quintessential to elucidate the commonality and differences of superconducting parameters in a mixed phase type I and type II SC of PdTe 2 [126]. In this regard, the role of transverse field (TF) muon spin rotation (μSR) technique becomes important which can probe the magnetic field expulsion (Meissner states) and vortex core or flux-line lattice (FLL) formation due to mixed states [126].…”