Polytypism, polymorphism, and superconductivity in TaSe2 - XTex

Huixia Luo, Weiwei Xie, Jing Tao, Hiroyuki Inouec, András Gyenis, Jason W. Krizan, Ali Yazdani, Yimei Zhu, Robert Joseph Cava

Research output: Contribution to journalArticlepeer-review

95 Scopus citations


Polymorphism in materials often leads to significantly different physical properties - the rutile and anatase polymorphs of TiO2 are a prime example. Polytypism is a special type of polymorphism, occurring in layered materials when the geometry of a repeating structural layer is maintained but the layer-stacking sequence of the overall crystal structure can be varied; SiC is an example of a material with many polytypes. Although polymorphs can have radically different physical properties, it is much rarer for polytypism to impact physical properties in a dramatic fashion. Here we study the effects of polytypism and polymorphism on the superconductivity of TaSe2, one of the archetypal members of the large family of layered dichalcogenides. We show that it is possible to access two stable polytypes and two stable polymorphs in the TaSe2-xTex solid solution and find that the 3R polytype shows a superconducting transition temperature that is between 6 and 17 times higher than that of the much more commonly found 2H polytype. The reason for this dramatic change is not apparent, but we propose that it arises either from a remarkable dependence of Tc on subtle differences in the characteristics of the single layers present or from a surprising effect of the layer-stacking sequence on electronic properties that are typically expected to be dominated by the properties of a single layer in materials of this kind.

Original languageEnglish (US)
Pages (from-to)E1174-E1180
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
StatePublished - Mar 17 2015

All Science Journal Classification (ASJC) codes

  • General


  • Charge-density wave
  • Dichalcogenide
  • Polymorphism
  • Polytypism
  • Superconductivity


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