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Zero-gap semiconductor to excitonic insulator transition in Ta2NiSe5

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Rost_2017_NatComms_Zero_gap_CC.pdf (714.2Kb)
Date
16/02/2017
Author
Lu, Y. F.
Kono, H.
Larkin, T. I.
Rost, A. W.
Takayama, T.
Boris, A. V.
Keimer, B.
Takagi, H.
Keywords
QC Physics
NDAS
BDC
R2C
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Abstract
The excitonic insulator is a long conjectured correlated electron phase of narrow-gap semiconductors and semimetals, driven by weakly screened electron–hole interactions. Having been proposed more than 50 years ago, conclusive experimental evidence for its existence remains elusive. Ta2NiSe5 is a narrow-gap semiconductor with a small one-electron bandgap EG of <50 meV. Below TC=326 K, a putative excitonic insulator is stabilized. Here we report an optical excitation gap Eop ∼0.16 eV below TC comparable to the estimated exciton binding energy EB. Specific heat measurements show the entropy associated with the transition being consistent with a primarily electronic origin. To further explore this physics, we map the TC–EG phase diagram tuning EG via chemical and physical pressure. The dome-like behaviour around EG∼0 combined with our transport, thermodynamic and optical results are fully consistent with an excitonic insulator phase in Ta2NiSe5.
Citation
Lu , Y F , Kono , H , Larkin , T I , Rost , A W , Takayama , T , Boris , A V , Keimer , B & Takagi , H 2017 , ' Zero-gap semiconductor to excitonic insulator transition in Ta 2 NiSe 5 ' , Nature Communications , vol. 8 , 14408 . https://doi.org/10.1038/ncomms14408
Publication
Nature Communications
Status
Peer reviewed
DOI
https://doi.org/10.1038/ncomms14408
ISSN
2041-1723
Type
Journal article
Rights
© The Author(s) 2017. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/
Description
This work was partially supported by Grant-in-Aid for Scientific Research (S; grant no. 24224010) and by Grant-in-Aid for Scientific Research on Innovative Areas (grant no. JP15H05852). H.T. acknowledges support from the Alexander von Humboldt foundation.
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  • University of St Andrews Research
URI
http://hdl.handle.net/10023/12357

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