ANOMALOUS DIELECTRIC-PROPERTIES OF AMORPHOUS SOLIDS AT LOW-TEMPERATURES

The dielectric response, epsilon'(omega) + i epsilon ''(omega), of amo rphous and glassy systems at low temperatures has been explained with considerable success by relaxation and resonant tunneling of independe nt tunneling two level systems (TLS) in response to an AC electric fie ld. However, recent measurements have shown an AC response to the appl ication of large DC electric fields which does not appear explicable i n terms of independent TLS, but instead may result from the formation of a hole in the density of states of the TLS at zero effective local electric field, similar to that postulated to exist in spin glasses. T his paper reports new studies of this response at very low temperature s which further support this interpretation, again suggesting that int eractions are important in understanding the dynamics of such systems at low temperatures.