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원자제어 저차원 전자계 연구단
원자제어 저차원 전자계 연구단
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Layer-Confined Excitonic Insulating Phase in Ultrathin Ta2NiSe5 Crystals

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Title
Layer-Confined Excitonic Insulating Phase in Ultrathin Ta2NiSe5 Crystals
Author(s)
Kim S.Y.; Kim Y.; Kang C.-J.; An E.-S.; Hyoung Kug Kim; Eom M.J.; Minkyung Lee; Chibeom Park; Tae-Hwan Kim; Hee Cheul Choi; Min B.I.; Kim J.S.
Publication Date
2016-09
Journal
ACS NANO, v.10, no.9, pp.8888 - 8894
Publisher
AMER CHEMICAL SOC
Abstract
Atomically thin nanosheets, as recently realized using van der Waals layered materials, offer a versatile platform for studying the stability and tunability of the correlated electron phases in the reduced dimension. Here, we investigate a thickness-dependent excitonic insulating (EI) phase on a layered ternary chalcogenide Ta2NiSe5. Using Raman spectroscopy, scanning tunneling spectroscopy, and in-plane transport measurements, we found no significant changes in crystalline and electronic structures as well as disorder strength in ultrathin Ta2NiSe5 crystals with a thickness down to five layers. The transition temperature, Tc, of ultrathin Ta2NiSe5 is reduced from its bulk value by ΔTc/Tc bulk ≈ -9%, which strongly contrasts the case of 1T-TiSe2, another excitonic insulator candidate, showing an increase of Tc by ΔTc/Tc bulk ≈ +30%. This difference is attributed to the dominance of interband Coulomb interaction over electron-phonon interaction and its zero-ordering wave vector due to the direct band gap structure of Ta2NiSe5. The out-of-plane correlating length of the EI phase is estimated to have monolayer thickness, suggesting that the EI phase in Ta2NiSe5 is highly layer-confined and in the strong coupling limit. © 2016 American Chemical Society
URI
https://pr.ibs.re.kr/handle/8788114/3276
ISSN
1936-0851
Appears in Collections:
Center for Artificial Low Dimensional Electronic Systems(원자제어 저차원 전자계 연구단) > Journal Papers (저널논문)
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