Arai Y, Kuroda Kenta, Nomoto T, Tin Z H, Sakuragi S, Bareille C, Akebi S, Kurokawa K, Kinoshita Y, Zhang W-L, Shin S, Tokunaga M, Kitazawa H, Haga Y, Suzuki H S, Miyasaka S, Tajima S, Iwasa K, Arita R, Kondo Takeshi
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Japan.
Graduate School of Advanced Science and Engineering, Hiroshima University, Higashihiroshima, Japan.
Nat Mater. 2022 Apr;21(4):410-415. doi: 10.1038/s41563-021-01188-9. Epub 2022 Feb 10.
Rare-earth intermetallic compounds exhibit rich phenomena induced by the interplay between localized f orbitals and conduction electrons. However, since the energy scale of the crystal-electric-field splitting is only a few millielectronvolts, the nature of the mobile electrons accompanied by collective crystal-electric-field excitations has not been unveiled. Here, we examine the low-energy electronic structures of CeSb through the anomalous magnetostructural transitions below the Néel temperature, 17 K, termed the 'devil's staircase', using laser angle-resolved photoemission, Raman and neutron scattering spectroscopies. We report another type of electron-boson coupling between mobile electrons and quadrupole crystal-electric-field excitations of the 4f orbitals, which renormalizes the Sb 5p band prominently, yielding a kink at a very low energy (7 meV). This coupling strength is strong and exhibits anomalous step-like enhancement during the devil's staircase transition, unveiling a new type of quasiparticle, named the 'multipole polaron', comprising a mobile electron dressed with a cloud of the quadrupole crystal-electric-field polarization.
稀土金属间化合物展现出由局域f轨道与传导电子之间相互作用所引发的丰富现象。然而，由于晶体电场分裂的能量尺度仅为几毫电子伏特，伴随集体晶体电场激发的移动电子的本质尚未被揭示。在此，我们利用激光角分辨光电子能谱、拉曼光谱和中子散射光谱，通过在奈尔温度（约17 K）以下被称为“魔鬼阶梯”的反常磁结构转变，研究了CeSb的低能电子结构。我们报道了移动电子与4f轨道的四极晶体电场激发之间的另一种电子 - 声子耦合，这种耦合显著重整了Sb 5p能带，在非常低的能量（约7毫电子伏特）处产生一个扭折。这种耦合强度很强，并且在魔鬼阶梯转变过程中呈现出反常的阶梯状增强，揭示了一种新型的准粒子，名为“多极极化子”，它由一个被四极晶体电场极化云包裹的移动电子组成。
