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Dr. Ang Chen's Lab                  

Research Interests

Landau – Ginzburg – Devonshire Phenomenal Theory

      It is well known that the electric-field dependence of the dielectric response can provide very useful information on the basic physics of dielectric polarization. However, dielectric response in polar dielectrics with respect to electric-fields, especially up to high field levels has been studied less. One main reason is lack of a theory (for instance a simple explicit function) to deal with dielectric spectra as a function of electric field.

      We have adopted the Landau-Ginzsburg-Devonshire (LGD) theory to treat the dc electric-field dependence of the relative dielectric constant er(E)  in polar dielectrics. It is found that the LGD theory works well in the case of a single polarization mechanism existing in the dielectrics and Johnson relation er(E)=er(0) / [1+ l(e0er(0))3E2]1/3 is a reasonable approximate expression describing er(E).

            Many polar dielectrics, however, exhibit more than one polarization mechanism contributing to the total dielectric constant. The dielectric response of such polar dielectrics under external dc electric field cannot be purely described by LGD theory. Hence, we introduce a “re-orientational polarization” to describe the “extrinsic” contribution to the dielectric constant, such as might arise from polar clusters, domain-wall motions, fluctuation of micro-clusters boundaries, defects, etc. A “multi-polarization-mechanism” model is proposed. For the details, please see the following paper.

CHEN Ang and ZHI Yu, DC electric-field dependence of the dielectric constant in polar dielectrics: “multi-polarization-mechanism” model, Physical Review B69, 174109 (2004) (8 pages).



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