A mechanism for the strange metal phase in rare-earth intermetallic compounds
稀土族金屬間化合物中奇異金屬相的形成機制

Jiangfan Wang, Yung-Yeh Chang, and Chung-Hou Chung*
Proceedings of the National Academy of Sciences (PNAS), 119, Vol. 10 , 1-9 (2022)
DOI: https://www.pnas.org/doi/10.1073/pnas.2116980119

The elusive strange metal phase (ground state) was observed in a variety of strongly correlated quantum materials at low temperatures, notably in f-electron–based rare-earth intermetallic compounds, showing quasi-linear-in-temperature resistivity and logarithmic-in-temperature specific heat coefficient. Its emergence has remained unclear, and constitutes one of the major outstanding open problems in condensed matter physics. Here, we propose a generic mechanism for this phenomenon driven by the interplay of the gapless fermionic short-ranged antiferromagnetic spin correlation and critical bosonic charge fluctuations near a Kondo breakdown quantum phase transition. It is manifested as a fluctuating Kondo scattering–stabilized critical (gapless) fermionic spin liquid. It shows ω/T scaling in dynamical electron scattering rate, a signature of quantum criticality. Our results on quasi-linear-in temperature scattering rate and logarithmic-in-temperature divergence in specific heat coefficient as temperature vanishes were recently observed in CePd1−xNixAl (Nat. Phys. 15, 1261–1266 (2019)).

近年來，一種令人費解的”奇異金屬相(量子基態)”已經廣泛地出現在各種低溫強關聯量子材料中,特別是在有局域化電子的稀土族金屬化合物中。這些奇異金屬現象的共同特點為: 隨溫度降低其電阻率呈現與溫度接近線性的方式下降,而比熱係數則以溫度的對數方式上升。目前此種奇異金屬態的形成原因與機制至今仍是凝態物理界公認的一大尚待解決的謎團。我們在本研究中提出了奇異金屬相形成的理論機制，此機制是基於在近藤消失量子相變點附近的無能隙費米子短程反鐵磁自旋關聯和臨界電荷玻色子擾動間的交互作用。 其基態表現出一種藉由近藤交互作用而穩定的”量子臨界(無能隙)費米自旋液體相”。 經由我們計算得到的動態電子散射率顯示出 ω/T 標度行為，這是典型的量子臨界特徵。在低溫時，我們預測此系統之比熱係數以對數形式發散以及電子散射率與溫度呈準線性關係。這兩種理論結果成功地解釋最近於 CePd1-xNixAl 的實驗中被觀察到的奇異金屬相 (Nat. Phys. 15, 1261–1266 (2019))。