Scholarlink

<p>Heavy fermions are commonly observed in <i>f</i>-electron Kondo systems. Several <i>d</i>-electron materials have been proposed as candidates for heavy fermion systems described by similar Kondo physics. In such systems, the flat <i>d</i>-orbital band near the Fermi energy (<i>E</i><sub><i>F</i></sub>) is considered to play a role analogous to that of the <i>f</i>-orbital band. However, the near-<i>E</i><sub><i>F</i></sub> flat band that induces Kondo coupling in a <i>d</i>-electron system has not been observed so far. Here, we investigate the electronic structure of a van der Waals ferromagnet Fe<sub>5−<i>x</i></sub>GeTe<sub>2</sub> with a transition temperature of about 300 K using angle-resolved photoemission spectroscopy. Our data demonstrates flat bands adjacent to the <i>E</i><sub><i>F</i></sub> in both quenched and slow-cooled samples. In the slow-cooled sample, we find two flat bands with quasiparticle peaks that develop below a specific temperature of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({T}^{{\prime} }\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi>T</mi> </mrow> <mrow> <mo>′</mo> </mrow> </msup> </math></EquationSource> </InlineEquation> (~100 K). Most importantly, one of these two flat bands develops an additional coherent spectral peak with heavy mass below 40 K, indicating that another transition occurs well below <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({T}^{{\prime} }\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi>T</mi> </mrow> <mrow> <mo>′</mo> </mrow> </msup> </math></EquationSource> </InlineEquation>. Around this temperature (~40 K), we find a transition from the non-Fermi-liquid to the Fermi-liquid state and a suppression of magnetization. Furthermore, STM measurements revealed a Fano line shape, signifying a resonant interaction between localized and itinerant channels. Our data consistently indicate that Fe<sub>5−<i>x</i></sub>GeTe<sub>2</sub> forms a Kondo lattice in both slow-cooled and quenched samples.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Observation of a d-orbital flat band near the Fermi level realizing a Kondo lattice in a van der Waals material

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年12月31日

查看全文
  • Soonsang Huh,
  • Kaishu Kawaguchi,
  • Masahiro Haze,
  • Yukio Hasegawa,
  • Yuyang Dong,
  • Kohei Aido,
  • Ayumi Harasawa,
  • Barnaby R. M. Smith,
  • Kohei Yamagami,
  • Yuita Fujisawa,
  • Chia-Hsiu Hsu,
  • Kenta Kuroda,
  • Hyun Jun Shin,
  • Jae Yeon Seo,
  • Nara Lee,
  • Young Jai Choi,
  • Yuto Kinoshita,
  • Masashi Tokunaga,
  • Makoto Hashimoto,
  • Donghui Lu,
  • Yoshinori Okada,
  • Takeshi Kondo

摘要

Heavy fermions are commonly observed in f-electron Kondo systems. Several d-electron materials have been proposed as candidates for heavy fermion systems described by similar Kondo physics. In such systems, the flat d-orbital band near the Fermi energy (EF) is considered to play a role analogous to that of the f-orbital band. However, the near-EF flat band that induces Kondo coupling in a d-electron system has not been observed so far. Here, we investigate the electronic structure of a van der Waals ferromagnet Fe5−xGeTe2 with a transition temperature of about 300 K using angle-resolved photoemission spectroscopy. Our data demonstrates flat bands adjacent to the EF in both quenched and slow-cooled samples. In the slow-cooled sample, we find two flat bands with quasiparticle peaks that develop below a specific temperature of \({T}^{{\prime} }\) T ′ (~100 K). Most importantly, one of these two flat bands develops an additional coherent spectral peak with heavy mass below 40 K, indicating that another transition occurs well below \({T}^{{\prime} }\) T ′ . Around this temperature (~40 K), we find a transition from the non-Fermi-liquid to the Fermi-liquid state and a suppression of magnetization. Furthermore, STM measurements revealed a Fano line shape, signifying a resonant interaction between localized and itinerant channels. Our data consistently indicate that Fe5−xGeTe2 forms a Kondo lattice in both slow-cooled and quenched samples.