Transition-metal dichalcogenides showing type-II Dirac fermions are emerging as innovative materials for nanoelectronics. However, their excitation spectrum is mostly unexplored yet. By means of high-resolution electron energy loss spectroscopy and density functional theory, here, we identify the collective excitations of type-II Dirac fermions (3D Dirac plasmons) in PtTe 2 single crystals. The observed plasmon energy in the long-wavelength limit is∼ 0.5 eV, which makes PtTe 2 suitable for near-infrared optoelectronic applications. We also demonstrate that interband transitions between the two Dirac bands in PtTe 2 give rise to additional excitations at∼ 1 and∼ 1.4 eV. Our results are crucial to bringing to fruition type-II Dirac semimetals in optoelectronics.
American Physical Society
22 Aug 2018
Volume: 121 Issue: 8 Pages: 086804
Physical review letters