Thermoelectric power and its correlation with conductivity in NbS3 whiskers
| Autor: | Woei Wu Pai, A. N. Vasiliev, V. V. Pryadun, S. G. Zybtsev, Olga S. Volkova, V. Ya. Pokrovskii, S. V. Zaitsev-Zotov, V. F. Nasretdinova, Damir Starešinić, E. S. Kozlyakova |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
Condensed matter physics 02 engineering and technology Conductivity Triclinic crystal system Atmospheric temperature range 021001 nanoscience & nanotechnology Elementary charge 01 natural sciences Heat capacity Seebeck coefficient 0103 physical sciences 010306 general physics 0210 nano-technology Charge density wave Monoclinic crystal system |
| Zdroj: | Physical Review B. 99 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.99.235155 |
| Popis: | We report studies of the Seebeck coefficient $S$ of the quasi-one-dimensional compound $\mathrm{Nb}{\mathrm{S}}_{3}$, together with the temperature dependence of its specific conductivity ${\ensuremath{\sigma}}_{\mathrm{s}}$ and heat capacity ${c}_{p}$. The monoclinic phase $(\mathrm{Nb}{\mathrm{S}}_{3}$-II) is studied over the temperature range $T=80--400$ K, which covers two charge density wave (CDW) transitions at ${T}_{\mathrm{P}1}=360$ K (CDW-1) and ${T}_{\mathrm{P}2}=150$ K (CDW-2). The $S(T)$ curves show features in the vicinities of both CDW transitions and appear to be correlated with the value of ${\ensuremath{\sigma}}_{\mathrm{s}}(300\phantom{\rule{0.28em}{0ex}}\mathrm{K})$: The increase of $S$ below ${T}_{\mathrm{P}1}$ in the high-Ohmic samples reveals a complete dielectrization of the electronic spectrum, while in the low-Ohmic samples $S$ decreases below ${T}_{\mathrm{P}1}$ and even becomes negative below ${T}_{\mathrm{P}2}$. The magnitude of $S$ in low-Ohmic samples at $Tl{T}_{\mathrm{P}2}$ is well below ${k}_{\mathrm{B}}/e\ensuremath{\approx}86\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{V}/\mathrm{K},{k}_{B}$ being the Boltzmann constant and $e$ the elementary charge, which is surprisingly low for a usual CDW semiconducting state. Our results suggest that at ${T}_{\mathrm{P}1}$ the main electronic band with $p$-type carriers becomes gapped, while some $n$-type carriers can remain in a separate band with low density of states. These carriers, whose concentration is defined by the compositional doping, are gapped at ${T}_{\mathrm{P}2}$. We also report $S$ for the triclinic dielectric phase of $\mathrm{Nb}{\mathrm{S}}_{3}\phantom{\rule{4pt}{0ex}}(\mathrm{Nb}{\mathrm{S}}_{3}\text{\ensuremath{-}}\mathrm{I})$. Its low absolute value, $\ensuremath{\sim}{k}_{\mathrm{B}}/e$, and the anomalous temperature dependence demonstrate that $\mathrm{Nb}{\mathrm{S}}_{3}\text{\ensuremath{-}}\mathrm{I}$ is neither a semiconductor nor a CDW conductor in the usual sense. |
| Databáze: | OpenAIRE |
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