Journal of the Korean Magnetics Society (한국자기학회지)

The Korean Magnetics Society (한국자기학회)
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ARPES Study of Quasi-Two Dimensional CDW System CeTe2

준이차원 전하밀도파 CeTe2의 각분해 광전자 분광 연구

  • Kim, D.H. (Department of Physics, The Catholic University of Korea) ;
  • Lee, H.J. (Department of Physics, The Catholic University of Korea) ;
  • Kang, J.S. (Department of Physics, The Catholic University of Korea) ;
  • Kim, H.D. (Pohang Accelerator Laboratory, POSTECH) ;
  • Min, B.H. (Department of Physics, Sungkyunkwan University) ;
  • Kwon, Y.S. (Department of Physics, Sungkyunkwan University) ;
  • Kim, J.W. (Department of Physics, POSTECH) ;
  • Min, B.I. (Department of Physics, POSTECH)
  • Received : 2010.09.07
  • Accepted : 2010.10.08
  • Published : 2010.10.31
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Abstract

The electronic structure of charge-density-wave (CDW) system $CeTe_2$ has been investigated by using angle-resolved photoemission spectroscopy (ARPES). The clearly dispersive band structures are observed in the measured ARPES spectra, indicating the good quality of the single-crystalline sample employed in this study. The four-fold symmetric patterns are observed in the constant energy (CE) mappings, indicating the $2{\times}2$ lattice deformation in the Te(1) sheets. The observed CE images are similar to those of $LaTe_2$, suggesting that Ce 4f states have the minor contribution to the CDW formation in $CeTe_2$. This study reveals that the carriers near the Fermi level should have mainly the Te(1) 5p and Ce 5d character, that the Te(1) 5p bands contribute to the CDW formation, and that the Ce 5d bands cross the Fermi level even in the CDW state.

이 연구에서는 각분해 광전자 분광법(angle-resolved photoemission spectroscopy: ARPES)을 시용하여 전하밀도파(chargedensity-wave: CDW)를 형성하는 물질인 $CeTe_2$의 전자구조를 연구하였다. $CeTe_2$의 ARPES 데이터에서는 분산적인 띠들이 분명하게 관찰되었다. $CeTe_2$의 일정에너지(constant energy: CE) 맵에서는 4중 대칭성(fourfold symmetry)이 관찰되었으며, 그 형태가 문헌에 있는 $CeTe_2$의 CE 맵과 유사하였다. 이러한 발견은 $CeTe_2$의 CDW 형성이 $2{\times}2$ 형태의 살창 변형에 의한 것임과 4f 전자들이 $CeTe_2$의 CDW 형성에 별다른 기여를 하지 않는다는 것을 나타낸다. 이 연구로부터 $CeTe_2$에서 페르미 준위 근처의 전자들은 주로 Te(1) 5p와 Ce 5d 전자들이며 Te(1) 5p 전자들에 의한 띠가 CDW 형성에 기여하고 Ce 5d 전자들에 의한 띠는 CDW 상태에서도 페르미 준위를 가로지르는 금속성을 나타낸다는 것을 알 수 있었다.

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