arXiv subjects
Publications and source records attributed to D. Staresinic.
In the present work we reply to the Comment by Catalan and Scott (cond-mat/0607500) on two of our papers. This Comment has been rejected from publication in Physical Review Letters and, hence, our Reply is based on the cond-mat version.
We present measurements of the dielectric response of quasi one-dimensional (TMTTF)2AsF6 in a wide temperature and frequency range. We provide a thorough characterization of the relaxational dynamics observed close to the ferroelectric-like transition at Tc = 100 K. Our measurements, extending up to 100 MHz, reveal a continuous slowing down of the mean relaxation time when approaching Tc from high as well as from low temperatures. The simultaneous critical rise of dielectric constant and relaxation time point to an explanation of the transition in terms of a classic ferroelectric scenario.
We show that the low temperature ($T<0.5$ K) time dependent non-exponential energy relaxation of quasi-one-dimensional (quasi-1D) compounds strongly differ according to the nature of their modulated ground state. For incommensurate ground states, such as in (TMTSF)$_2$PF$_6$ the relaxation time distribution is homogeneously shifted to larger time when the duration of the heat input is increased, and exhibits in addition a scaling between the width and the position of the peak in the relaxation time distribution, $w^{2}\sim\ln{(τ_{m})}$. For a commensurate ground state, as in (TMTTF)$_2$PF$_6$, the relaxation time spectra show a bimodal character with a weight transfer between well separated slow and fast entities. Our interpretation is based on the dynamics of defects in the modulated structure, which depend crucially on the degree of commensurability.
We report on broadband dielectric spectroscopy on the one-dimensional semiconductor (NbSe4)3I. Below the structural phase transition close to 270 K we observe colossal dielectric constants with a frequency and temperature dependence very similar to what is observed in canonical charge-density wave systems. Guided by structural details we interpret this structural phase transition as driven by complex charge-order processes.
Measurements of the magnetic susceptibility and its anisotropy in the quasi-one-dimensional system o-TaS_{3} in its low-T charge density wave (CDW) ground state are reported. Both sets of data reveal below 40 K an extra paramagnetic contribution obeying a power-law temperature dependence χ(T)=AT^{-0.7}. The fact that the extra term measured previously in specific heat in zero field, ascribed to low-energy CDW excitations, also follows a power law C_{LEE}(0,T)=CT^{0.3}, strongly revives the case of random exchange spin chains. Introduced impurities (0.5% Nb) only increase the amplitude C, but do not change essentially the exponent. Within the two-level system (TLS) model, we estimate from the amplitudes A and C that there is one TLS with a spin s=1/2 localized on the chain at the lattice site per cca 900 Ta atoms. We discuss the possibility that it is the charge frozen within a soliton-network below the glass transition T_{g}~40 K determined recently in this system.