Robin Nicholas

Abstract:

Cyclotron resonance measurements in the highly polar (α = 0.29) semiconductor InSe are reported in pulsed magnetic fields up to 37 T. For B > 18 T two cyclotron branches are found which are a consequence of the resonant polaron interaction. This is the first time that both branches have been observed simultaneously in 2D, and both are observed over a range of more than 10 T. The splitting is approximately 40% of the optical phonon energy which results in a change in effective mass of a factor of two between the upper and lower branches. A detailed comparison is made with a theory for the cyclotron resonance spectrum. A second, much weaker resonant interaction is found for B ≈ 18 T. This is due to a resonant interaction with homopolar phonons and a theory is constructed for this interaction. At resonance the splitting is a very sensitive function of the interaction strength, allowing accurate determination of the coupling constant g2 = 0.001. © 1992.

Abstract:

Resonant polaron coupling has been observed by cyclotron resonance of two-dimensional electrons in the polar semiconductor InSe. Both upper and lower branches of the magnetopolaron are seen over a wide range of field (B=18-34 T), allowing an accurate test of polaron theories. A homopolar phonon is also observed to give resonant coupling, via a deformation potential, and we present a theoretical treatment of this coupling mechanism. This gives an accurate value of g2=0.001 0.0005 for the coupling constant. © 1992 The American Physical Society.