Enhanced superconductivity originating from f -electron doping in topologically nontrivial YPdBi half-Heusler thin films

Journal article, 2024

YPdBi is a well-studied diamagnetic topologically trivial half-Heusler alloy that is superconducting with Tc∼1 K. When strained or in thin-film form, it shows a topologically nontrivial surface state with Tc ∼1.25K. ErPdBi is a well-studied topologically nontrivial half Heusler with Tc ∼1.22K. In this work, we demonstrate that the f-electron doping in YPdBi provides a unique way to selectively tune the electronic structure and aid in increasing the superconducting transition temperature of YPdBi. This work presents systematic measurements of electrical resistivity and magnetotransport on half-Heusler thin films of Y(1-x)ErxPdBi (x=0.2, 0.5, and 0.8), prepared using the pulsed laser deposition technique. All the films were observed to be semimetallic, with a sharp downturn in resistivity at low temperatures T < 5 K; the E5 film (Tc∼4.4 K) and E8 film (Tc∼3.7 K) reach a zero-resistivity value, within the experimental limit. The doping of f electron on Y+3 sites possibly gives rise to the improved Fermi parameters and an increase in Tc. Magnetoresistance measurements and first-principle calculations support that Y(1-x)ErxPdBi are topologically nontrivial semimetals. The first-principle calculations also show that with an increase in the doping concentration (x), more f bands start to appear near Fermi level (EF), giving rise to an increase in the band-inversion strength due to s-f exchange interaction. The nontrivial band structure, odd-parity Cooper pair, and noncentrosymmetric crystal structure suggest the presence of unconventional superconductivity in the E5 and E8 films.