Thermoelectric power and its correlation with conductivity in NbS3 whiskersстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 15 августа 2019 г.
Аннотация:We report studies of the Seebeck coefficient S(T) of the quasi-one-dimensional compound NbS3, together with the temperature dependence of its specific conductivity and heat capacity. The monoclinic phase (NbS3-II) is studied over the temperature range T=80–400 K, which covers two charge density wave (CDW) transitions at TP1=360 K (CDW-1) and TP2=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 σs(300K): The increase of S below TP1 in the high-Ohmic samples reveals a complete dielectrization of the electronic spectrum, while in the low-Ohmic samples S decreases below TP1 and even becomes negative below TP2. The magnitude of S in low-Ohmic samples at T<TP2 is well below kB/e≈86μV/K, kB being the Boltzmann constant and e the elementary charge, which is surprisingly low for a usual CDW semiconducting state. Our results suggest that at TP1 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 TP2. We also report
S for the triclinic dielectric phase of NbS3 (NbS3−I). Its low absolute value, ∼kB/e, and the anomalous temperature dependence demonstrate that NbS3−I is neither a semiconductor nor a CDW conductor in the usual sense.