Fig. 3

Shapiro steps. a Shapiro steps response of the structure No. 4 to the application of an external RF-field for various frequencies of the same amplitude 400 mV at B = 20T and T = 4.2 K. b Variation of the interchain voltage ΔV vs. frequency of an external radiation f for all measured structures. c dI/dV(I) for different temperatures at B = 16T and the external frequency f = 176 MHz (sample No. 7). Temperature increases from 7 K (lower curve) up to 29 K (upper curve) with the step ΔT = 1 K. d Temperature variation of ΔV