Unusual electronic properties of a low-temperature phase of Ag₄SSe

Titelangaben

Matteppanavar, Shidaling ; Bui, Nguyen Hai An ; Ramakrishnan, Srinivasan ; Vagadia, Megha ; Thamizhavel, Arumugam ; Paul, Arpita ; Waghmare, Umesh V. ; Schönleber, Andreas ; van Smaalen, Sander:
Unusual electronic properties of a low-temperature phase of Ag₄SSe.
In: Physical Review Materials. Bd. 2 (2018) . - 113606.
ISSN 2475-9953
DOI: https://doi.org/10.1103/PhysRevMaterials.2.113606

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Abstract

The superionic electrical conductor Ag4SSe is reported to undergo an unusual first-order structural phase transition at ∼260K with concomitant anomalous electronic properties. Single-crystal x-ray diffraction reveals that the crystal undergoes a structural transition from monoclinic α−Ag4SSe to an orthorhombic crystal structure below 260 K. The new low-temperature phase is denoted as δ−Ag4SSe, and it is found to be isostructural to α−Ag2Se. The diamagnetic magnetic susceptibility is of larger magnitude in the low-temperature δ phase than in α−Ag4SSe. A diamagnetic susceptibility of larger magnitude is usually related to a lower density of states at the Fermi level which leads to a decrease in the Pauli paramagnetic susceptibility. However, we find δ−Ag4SSe to be metallic with a much lower resistivity than semiconducting α−Ag4SSe. As a consequence, the α−δ structural phase transition of Ag4SSe causes an unusual Fermi surface reconstruction with an increased mobility of charge carriers and unexpected metallic behavior in δ−Ag4SSe. Band structure calculations substantiate such a claim. In addition, we also observe spontaneous voltage generation (SVG) at the phase transition, which has previously been observed only in a few magnetic materials.