九州大学大学院理学研究院物理学部門
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Superconductivity and CDW

The RPt2Si2 compounds, where R stands for a rare-earth element, have the tetragonal CaBe2Ge2-type structure. YPt2Si2 and LaPt2Si2 are superconductors with TC of 2 K. On the other hand, the compounds with R = La and Pr show anomalies at around 100 K in the temperature dependence of electrical resistivity (left panel). Previous studies have suggested the occurrence of charge density wave (CDW). Therefore, LaPt2Si2 is a possible material in which CDW and superconductivity coexist. To elucidate the origin of the first-order phase transition of LaPt2Si2, we have performed diffraction measurements on LaPt2Si2 at low temperatures.
Low temperature X-ray diffraction measurements have revealed that
LaPt2Si2 has an orthorhombic symmetry below T*. Moreover, he selected area electron diffraction patterns show (n/3 0 0) superlattice reflections with n = 1 and 2 at 10 K (light panel). These results are convincing evidence of the CDW formation in LaPt2Si2. The compounds with R = Y, La, Lu show a superconducting transition with Tc = 1.5 ~ 1.9 K. T­hese results indicate that superconductivity coexists with CDW in LaPt2Si2 but not in YPt2Si2 and LuPt2Si2. We found that the CDW formation is closely correlated with the interatomic distance in the basal plane. To explain no significant relation between CDW and superconductivity in RPt2Si2 , we propose that CDW takes place in different PtSi block layers. In order to clarify this point, further experiments are in progress.  

References

Charge Density Wave and Superconductivity of RPt2Si2 (R = Y, La, Nd, and Lu), Yutaro Nagano, Nobutaka Araoka, Akihiro Mitsuda, Hideki Yayama, Hirofumi Wada, Masaki Ichihara, Masahiko Isobe and Yutaka Ueda, J. Phys. Soc. Jpn. vol. 82 (2013) 064715 (5 pages).

 
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