Experimental investigation of a regime of Wigner ergodicity in microwave rough billiards

We study experimentally a new regime of Wigner ergodicity [K.M. Frahm and D.L. Shepelyansky, Phys. Rev. Lett. 79, 1833 (1997)] in a microwave rough billiard. We show that in the Wigner regime, eigenstates are extended over the whole energy surface but have a strongly peaked nonergodic structure. The Shannon width of the eigenstate distributions is calculated to estimate their spreads and to find their departure from the ergodic distributions.