Cyclotron Phase-Resonance Transmission in Copper

In a field-normal microwave-frequency transmission experiment we observe strong resonant oscillatory bursts of microwave-field transmission through sheets of single-crystal copper. These bursts occur at field values appropriate to cyclotron resonance and its harmonics, but are not associated with Azbel'-Kaner cyclotron resonance. Instead we attribute the effect to a mechanism in which electrons propagating across the sample all arrive at the second surface with the same microwave phase, whenever the dc magnetic field satisfies the condition for cyclotron resonance.