Ultrafast quasiparticle dynamics in the heavy-fermion compound YbRh2Si2
Ultrafast quasiparticle dynamics in the heavy-fermion compound YbRh2Si2
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DOI：
10.1103/physrevb.86.085139
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发表时间：
2012-08
影响因子：
3.7
通讯作者：
K. Kummer;D. Vyalikh;Laurenz Rettig;R. Cortés;Y. Kucherenko;C. Krellner;C. Geibel;U. Bovensiepen
中科院分区：
文献类型：
--
作者：
K. Kummer;D. Vyalikh;Laurenz Rettig;R. Cortés;Y. Kucherenko;C. Krellner;C. Geibel;U. Bovensiepen
了解强相关稀土金属间化合物需要了解费米能级 ${E}_{\mathrm{F}}$ 附近状态下费米子准粒子的性质。我们报告了使用飞秒时间和角度分辨光电子能谱来确定重费米子化合物 YbRh${}_{2}$Si${}_{2}$ 中热准粒子寿命的泵浦探针实验。在 $\overline{\ensuremath{\Gamma}}$ 处发现了一个具有类电子色散的未占据能带，其带底高于 ${E}_{\mathrm{F}}$ 0.2 eV，与地下区域的能带结构计算一致。对于高于 ${E}_{\mathrm{F}}$ 0.4 至 $0.1$ eV 的能量，发现热准粒子寿命为 30 至 80 fs。这些寿命通常遵循典型的向 ${E}_{\mathrm{F}}$ 单调增加的规律，与早期对 Yb 和 Rh 元素金属的研究一致。然而，在正常发射时，0.2 eV 左右的寿命超出了这一趋势约 $+20$ fs。这种差异随着光电发射角的增加而减小，并且可以分配给在 YbRh${}_{2}$Si${}_{2}$ 中探测的特定带。讨论了潜在的微观场景。
Understanding strongly correlated rare-earth intermetallic compounds requires knowledge of the nature of the fermionic quasiparticles in states near the Fermi level ${E}_{\mathrm{F}}$. We report on a pump-probe experiment using femtosecond time- and angle-resolved photoemission spectroscopy to determine lifetimes of hot quasiparticles in the heavy-fermion compound YbRh${}_{2}$Si${}_{2}$. An unoccupied band with electronlike dispersion and a band bottom 0.2 eV above ${E}_{\mathrm{F}}$ was identified at $\overline{\ensuremath{\Gamma}}$, in agreement with band structure calculations for the subsurface region. Hot quasiparticle lifetimes from 30 to 80 fs were found for energies between 0.4 and $0.1$ eV above ${E}_{\mathrm{F}}$. These lifetimes generally follow the typical monotonous increase towards ${E}_{\mathrm{F}}$, in agreement with earlier studies on Yb and Rh elemental metals. However, at normal emission the lifetimes at around 0.2 eV exceed this trend by about $+20$ fs. This difference decreases with increasing photoemission angle and can be assigned to the particular band that is probed in YbRh${}_{2}$Si${}_{2}$. Potential microscopic scenarios are discussed.