Incommensurate systems as model compounds for disorder revealing low-temperature glasslike behavior.

We show that the specific heat of incommensurately modulated crystals with broken translational periodicity presents similar features at low temperatures to those of amorphous and glass materials. Here we demonstrate that the excess to the constant C_{p}(T)/T^{3} law (or Debye limit) is made up of an upturn below 1 K and of a broad bump at T≈10 K that directly originates from the gapped phase and amplitude modes of the incommensurate structure. We argue that the low-energy dynamics of incommensurate systems constitute a plausible simplification of the landscape of interactions present in glasses, giving rise to their low-temperature anomalies.

The influence of temperature and electric field history on the conductivity of the charge density wave system o-TaS3.

We have studied the dependence of the low electric field conductivity of the charge density wave (CDW) system o-TaS(3) on the temperature and applied electric field history. Without the application of high electric fields, the conductivity is higher on cooling than on heating in a wide temperature range below the CDW transition. With the application of increasing field at a given temperature the conductivity evolves towards a stable, history-independent value situated between the cooling and heating values. The evolution is gradual but most pronounced around the threshold field for nonlinear conductivity. The relative change of conductivity after the application of high field is asymmetric in respect of the temperature history. We discuss the results within the model of quantized changes of the CDW wavelength induced by the variation of the temperature and the electric field.

Freezing of low energy excitations in charge density wave glasses.

Thermally stimulated discharge current measurements were performed to study slow relaxation processes in two canonical charge density wave systems K(0.3)MoO(3) and o-TaS(3). Two relaxation processes were observed and characterized in each system, corroborating the results of dielectric spectroscopy. Our results are consistent with the scenario of the glass transition on the charge density wave superstructure level. In particular, the results directly prove the previously proposed criterion of charge density wave freezing based on the interplay of charge density wave pinning by impurities and screening by free carriers. In addition, we obtained new information on distribution of relaxation parameters, as well as on nonlinear dielectric response both below and above the threshold field for charge density wave sliding.

Giant dielectric response in the one-dimensional charge-ordered semiconductor (NbSe4)3I.

We report on broadband dielectric spectroscopy on the one-dimensional semiconductor (NbSe4)3I. Below the structural phase transition close to 270 K, which is accompanied by complex charge-order processes, we observe colossal dielectric constants with a frequency and temperature dependence very similar to what is observed in charge-density wave systems.