We present a combined study of the thermal expansion and the thermal conductivity of the perovskite series RCoO_3 with R = La, Nd, Pr and Eu. The well-known spin-state transition in LaCoO_3 is strongly affected by the exchange of the R ions due to their different ionic radii, i.e. chemical pressure. This can be monitored in detail by measurements of the thermal expansion, which is a highly sensitive probe for detecting spin-state transitions. The Co ions in the higher spin state act as additional scattering centers for phonons, therefore suppressing the phonon thermal conductivity. Based on the analysis of the interplay between spin-state transition and heat transport, we present a quantitative model of the thermal conductivity for the entire series. In PrCoO_3, an additional scattering effect is active at low temperatures. This effect arises from the crystal field splitting of the 4f multiplet, which allows for resonant scattering of phonons between the various 4f levels.
Phonon renormalization effects accompanying the 6 K anomaly in the Quantum Spin Liquid Candidate $κ$-(BEDT-TTF)$_{2}$Cu$_{2}$(CN)$_{3}$
量子自旋液体候选物$κ$ -（BEDT-TTF）$_{2}$ Cu $_{2}$（CN）$_{3}$的低温状态通过$T^{*}\sim6$ K处的异常出现。虽然这种异常现象的特征已被揭示出不同的数量，但其起源仍不清楚。本文报道了$κ$ -（BEDT-TTF）$_{2}$ Cu $_{2}$（CN）$_{3}$单晶的非弹性中子散射测量，旨在研究$T^{*}$的声子重整化效应。在$E=4.7$ meV的BEDT-TTF二聚体的呼吸模式下，在$T^{*}$上观察到声子阻尼的急剧变化。声子阻尼的突变是由于相变成价键固态的基础上描述的自旋-电荷耦合在这个二聚体-莫特系统的有效模型。
Spinons and damped phonons in spin-1/2 quantum-liquid Ba$_{4}$Ir${}_3$O${}_{10}$ observed by Raman scattering
在自旋为1/2的莫特绝缘体中，当系统没有表现出磁性有序时，通常会出现非磁性量子液相，但识别这些相或相关自旋准粒子的正签名可能是难以捉摸的。本文利用Raman散射研究了自旋轨道量子液体材料Ba ${}_4$ Ir ${}_3$ O ${}_{10}$中自旋子的三个特征：（1）在Raman散射中，当Luttinger液体自旋子的光子极化方向平行于一维链时，会产生一个宽峰;以及（3）当2%的Ba被Sr取代时产生的磁有序相（（Ba ${}_{0.98}$ Sr ${}_{0.02}$）${}_4$ Ir ${}_3$ O ${}_{10}$）中不存在（1）和（2）。在这种量子液体绝缘体中看到的通过巡回自旋的声子阻尼表明了一种新的机制，通过中性量子液体来增强强相关导体中的热电性，而不需要影响电子输运。
Exciton interacting with the phonons of an electronic Wigner crystal
Aarhus University（奥胡斯大学）；University of Copenhagen（哥本哈根大学）；University of California, Santa Barbara（加州大学圣巴巴拉分校）；Accademia di Danimarca – The Danish Academy for Science and Art in Rome（丹麦艺术与科学院）
