Cyclotron Resonance in Extremely Low Carrier-Density System of Yb₄As₃

We report on the cyclotron resonance (CR) measurements performed on Yb₄As₃ using the cavity perturbation (TE₁₀₁ and TE₁₀₂) and simple transmission techniques without a cavity for microwaves (16-110 GHz) at 22 ≥ T ≥ 0.55 K and H ≤ 10 T. CR and electron spin resonance (ESR) have identified each other by the systematic comparison of the data obtained from the three different measurement techniques performed. The CR that is symmetric and strongly temperature-dependent has a CR mass of 0.72m₀, while the ESR which is rather antisymmetric and very weakly temperature-dependent, has g = 2.04. The comparison of the CR mass with the recent band structure calculations based on the LAPW method concludes that the observed CR is caused by the light 4p-holes of As ions centered at the г point, the band mass of which is calculated to be about 0.7m₀. We discuss the temperature dependence of the electron relaxation time obtained by the linewidth analysis performed for the CR.