Easily Accessible Topologically Protected Charge Carriers in Pure and Robust α‐Sn Films

Experimental evidence of topological Dirac fermion charge carriers in pure and robust α‐Sn thin films grown on InSb substrates is reported. This evidence is acquired using standard macroscopic four‐point contact resistance measurements, conducted on uncapped films with a significantly reduced bulk mobility. The electrical characteristics of the constituting components of the α‐Sn/InSb sample are analyzed and compared and a three‐band drift velocity model is proposed accordingly. A surface band, with low carrier density and high mobility, is identified as the origin of the observed Shubnikov – de Haas (SdH) oscillations. The analysis of these quantum oscillations results in a nontrivial value of the phase shift γ0, characteristic of topologically protected Dirac fermions. The momentum relaxation time τ ≈ 300 fs in pure, undoped α‐Sn thin films is estimated. Herein, the existence of topological Dirac fermion charge carriers, detected by standard electronic transport measurements, in strained elemental α‐Sn is shown unambiguously. The detection of these kinds of exotic carriers in quantum materials by transport measurements is extremely rare. Moreover, the detected topologically protected charge carriers example an exceptionally long momentum relaxation time.