Datensatz

Zusammenfassung

The complex optical conductivity of the half-Heusler compound GdPtBi is measured in a frequency range from 20 to 22 000 cm(-1) (2.5 meV-2.73 eV) at temperatures down to 10 K in zero magnetic field. We find the real part of the conductivity, sigma(1) (omega), to be almost perfectly linear in frequency over a broad range from 50 to 800 cm(-1) (similar to 6-100 meV) for T <= 50 K. This linearity strongly suggests the presence of three-dimensional linear electronic bands with band crossings (nodes) near the chemical potential. Band-structure calculations show the presence of triple points, where one doubly degenerate and one nondegenerate band cross each other in close vicinity of the chemical potential. From a comparison of our data with the optical conductivity computed from the band structure, we conclude that the observed nearly linear sigma(1)(omega) originates as a cumulative effect from all the transitions near the triple points.