Quantum octets in high mobility pentagonal two-dimensional PdSe2.

Two-dimensional (2D) materials have drawn immense interests in scientific and technological communities, owing to their extraordinary properties and their tunability by gating, proximity, strain and external fields. For electronic applications, an ideal 2D material would have high mobility, air stability, sizable band gap, and be compatible with large scale synthesis. Here we demonstrate air stable field effect transistors using atomically thin few-layer PdSe₂ sheets that are sandwiched between hexagonal BN (hBN), with large saturation current > 350 μA/μm, and high field effect mobilities of ~ 700 and 10,000 cm²/Vs at 300 K and 2 K, respectively. At low temperatures, magnetotransport studies reveal unique octets in quantum oscillations that persist at all densities, arising from 2-fold spin and 4-fold valley degeneracies, which can be broken by in-plane and out-of-plane magnetic fields toward quantum Hall spin and orbital ferromagnetism. Here, the authors report the characterization of stable few-layer PdSe₂ transistors encapsulated in hexagonal boron nitride, showing field effect mobilities up to 700 cm²/Vs at room temperature and signatures of an 8-fold spin-valley degeneracy of the magnetotransport quantum oscillations at cryogenic temperatures. [ABSTRACT FROM AUTHOR]