Nodeless superconductivity in the type-II Dirac semimetal PdTe2: London penetration depth and pairing-symmetry analysis*

London penetration depth and normal-state resistivity were measured in single crystals of type-II Dirac semimetal PdTe2. Superfluid density is exponential at low temperatures and follows single-gap BCS model with weak-coupling Delta(0)/Tc = 1.76 in the whole temperature range. Electrical resistivity is compatible with a classical metal with dominant electron-phonon scattering obtained from the fit to Bloch-Grüneisen formula with a Debye temperature of 207 K from specific heat data. We compare these experimental results with expectations from a detailed theoretical symmetry analysis and reduce the number of possible superconducting pairing states in PdTe2 to only three nodeless candidates: a regular, topologically trivial s-wave pairing, and two distinct odd-parity triplet states that both can be topologically nontrivial depending on the microscopic interactions driving the superconducting instability. Finally, we theoretically discuss the effect of disorder on the different pairing states.