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Universal superlinear power law



universal repsonse A zoo of techniques, covering the exceptional broad range from ultra-low, over radio- and microwave frequencies up to the frequencies of visible light has been used to measure the frequency dependence of the real part of the dielectric constant and the real part of the conductivity (proportional to the absorbtivity), and hence to study the interaction of electromagnetic radiation with disordered condensed matter. The authors provide convincing experimental evidence that the interaction is universal for as different materials as molecular and ionic liquids, supercooled liquids and glasses, ionic conductors and doped or disordered semiconductors. Specifically at high frequencies, from the microwave to the visible regime, all materials reveal the same universal superlinear power law (SLPL) of the conductivity with a frequency exponent between one and two (see Fig.). This observation is of prime importance for different fields in natural sciences: An increasing number of electronic devices, e.g. in wireless communications or computer techniques operate at progressively higher frequencies and the knowledge of the absorption processes is an important input parameter for the design of new devices or the use of new materials. But this observation also helps to understand the interaction of electromagnetic waves with biological matter. The frequency range investigated covers the complete range of non-ionising radiation. Its biological effects can only be estimated on the basis of this observation of universal absorption processes in molecular liquids.

To learn more, see: P. Lunkenheimer and A. Loidl, Phys. Rev. Lett. 91, 207601 (2003).