Giant response to electric fields

in a one-dimensional semiconductor

We show that (NbSe4)3I, a one-dimensional semiconductor whose crystalline structure forces electrons to move only in one direction, exhibits an amazingly large dielectric constant, i.e. it has an extremely high ability to store electric charges when subjected to an electric field.
In contrast to most current reports of "colossal" dielectric constants in a variety of materials, the values up to 150000 found in our work are a truly intrinsic property and not due to surface polarization. In addition, in ac fields the dielectric constant of this material shows a strong frequency dependence, indicating relaxational processes, i.e. the polarization cannot follow the quickly varying field at high frequencies. These phenomena are surprisingly similar to the findings in the so-called "charge density wave" systems, where the electron density is arranged in wave-like patterns, but the theoretical models developed for this class of materials cannot easily be applied to this one-dimensional charge-ordered semiconductor. Thus it seems likely that a completely new mechanism of electric polarization prevails in this material and one may speculate about one-dimensional ferroelectricity and/or an important role of electronic degrees of freedom to explain the giant dielectric response of (NbSe4)3I. large dielectric constant

Temperature dependent dielectric constant of (NbSe4)3I for various frequencies exhibiting colossal values up to 150000.

To learn more, see: D. Starešinic, P. Lunkenheimer, J. Hemberger, K. Biljakovic, and A. Loidl, Giant dielectric response in the one-dimensional charge-ordered semiconductor (NbSe4)3I, Phys. Rev. Lett. 96, 046402 (2006), (cond-mat/0504675).