Features of a Low-Temperature Charge Density Wave in the Monoclinic Phase of NbS3 Manifested in the NMR and in Transport Properties

Abstract

<p>The relaxation of the transverse nuclear magnetization in the monoclinic phase of NbS₃ has been studied by the ⁹³Nb nuclear magnetic resonance method near the temperature <em>T</em>_P2 = 150 K, at which a low-temperature charge density wave is formed. It has been shown that the critical slowing down of one of the vibrational modes of the lattice, which is quite slow even above <em>T</em>_P2, occurs slightly below <em>T</em>_P2. The transition at <em>T</em>_P2 occurs not only in low-resistance samples, as thought previously, but also in high-resistance ones, and involves Nb atoms in the bulk of a sample. The transport properties of high-resistance samples, namely, the smearing of the depinning threshold for the charge density wave below <em>T</em>_P2, confirm that the phase transition in them occurs at <em>T</em>_P2. It has been concluded that the distortion of the lattice at <em>T</em>_P2 is not due to the Peierls mechanism and can be attributed to the Keldysh–Kopaev transition. Another possible mechanism is the fluctuation distortion of the lattice above <em>T</em>_P2 that prevents the sliding of the charge density wave.<br></p>