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Singular charge fluctuations at a magnetic quantum critical point
Science ( IF 56.9 ) Pub Date : 2020-01-16 , DOI: 10.1126/science.aag1595
L Prochaska 1 , X Li 2 , D C MacFarland 1, 3 , A M Andrews 3 , M Bonta 4 , E F Bianco 5 , S Yazdi 6 , W Schrenk 7 , H Detz 7 , A Limbeck 4 , Q Si 8 , E Ringe 6 , G Strasser 3, 7 , J Kono 2, 6, 8 , S Paschen 1, 8
Affiliation  

Spin-charge entanglement Many physical properties follow characteristic scaling laws near quantum critical points, which are associated with phase transitions at absolute zero temperature. The material YbRh2Si2 has an antiferromagnetic quantum critical point, where spin-related properties are expected to follow such a scaling. Unexpectedly, Prochaska et al. found that charge fluctuations follow a critical scaling as well. The researchers fabricated high-quality thin films of YbRh2Si2 and used transmission spectroscopy to measure the optical conductivity of the film and infer the scaling. Their findings point to a highly entangled state of charge and spin, which may also be responsible for the strangemetal phase in this material. Science, this issue p. 285 Optical conductivity measurements on thin films of YbRh2Si2 point to entanglement of spin and charge in this material. Strange metal behavior is ubiquitous in correlated materials, ranging from cuprate superconductors to bilayer graphene, and may arise from physics beyond the quantum fluctuations of a Landau order parameter. In quantum-critical heavy-fermion antiferromagnets, such physics may be realized as critical Kondo entanglement of spin and charge and probed with optical conductivity. We present terahertz time-domain transmission spectroscopy on molecular beam epitaxy–grown thin films of YbRh2Si2, a model strange-metal compound. We observed frequency over temperature scaling of the optical conductivity as a hallmark of beyond-Landau quantum criticality. Our discovery suggests that critical charge fluctuations play a central role in the strange metal behavior, elucidating one of the long-standing mysteries of correlated quantum matter.

中文翻译:

磁量子临界点处的奇异电荷涨落

自旋电荷纠缠 许多物理性质遵循量子临界点附近的特征标度定律,这与绝对零温度下的相变有关。材料 YbRh2Si2 具有反铁磁量子临界点,预计与自旋相关的特性将遵循这样的比例。出乎意料的是,Prochaska 等人。发现电荷波动也遵循临界缩放。研究人员制造了高质量的 YbRh2Si2 薄膜,并使用透射光谱来测量薄膜的光导率并推断缩放比例。他们的发现指出了高度纠缠的电荷和自旋状态,这也可能是这种材料中奇异金属相的原因。科学,这个问题 p。285 YbRh2Si2 薄膜的光导率测量表明该材料中的自旋和电荷纠缠。奇怪的金属行为在相关材料中无处不在,从铜酸盐超导体到双层石墨烯,并且可能来自于朗道级参数量子涨落之外的物理学。在量子临界重费米子反铁磁体中,这种物理可以实现为自旋和电荷的临界近藤纠缠,并用光导率探测。我们在分子束外延生长的 YbRh2Si2 薄膜上展示了太赫兹时域透射光谱,YbRh2Si2 是一种模型奇异金属化合物。我们观察到光导率随温度变化的频率作为超越朗道量子临界性的标志。
更新日期:2020-01-16
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