Department of Magnetic Reseach Seminar

Dirac states in Pd-Bi superconductors: on the hunt for Majorana modes

prof. Dr hab. Dariusz Kaczorowski

Topological superconductor (TSC) hosting Majorana fermions has been established as a milestone that might shift our scientific trajectory from fundamental research to practical applications in topological quantum computing. Recently, superconducting Pd-Bi binaries, due to their inherently large spin-orbit coupling strength, have attracted much attention as a possible platform for realization of the TSC phase.

Here, we present the electrical transport and thermodynamic properties of two such binaries, namely α-PdBi₂ (T_c = 1.7 K), crystallizing with a monoclinic centrosymmetric unit cell (space group C2/m) [1], and PdBi (T_c = 3.7 K), forming with a monoclinic noncentrosymmetric crystal structure (space group P12₁1) [2]. Then, we discuss the results of our comprehensive studies on the electronic structures of these compounds by means of high-resolution angle- and spin-resolved photoemission spectroscopy (ARPES) and ab-initio band structure calculations [1,2].

In each material we observed Dirac states at high binding energy with a Dirac node located at about 0.7 and 1.26 eV below the chemical potential for mono- and dibismuthide, respectively. In the case of PdBi, the absence of spin-polarized surface states near the Fermi level negates the possibility that this system might host topological superconductivity on the surface. In turn, for α-PdBi₂, multiple surface Rashba states were found in the vicinity of the chemical potential, which might be utilized to realize Majorana fermions [4].

This research was supported by the National Science Centre (Poland) under grant no. 2015/18/A/ST3/00057.

[1] K. Dimitri, et al., Phys. Rev. B 97, 144514 (2018).
[2] M. Neupane, et al., Nat. Comm. 7, 13315 (2016).
[3] A. C. Potter and P. A. Lee, Phys. Rev. B 85, 094516 (2012).