标题： 间隙滑动声子在非共格复合晶体Sr$_{14}$Cu$_{24}$O$_{41}$中的过量比热 显示英文标题

标题： Excess speicific heat of the gapped sliding phonons in the incommensurate composite crystal Sr$_{14}$Cu$_{24}$O$_{41}$

摘要： 我们证明，非共格链梯系统Sr$_{14}$Cu$_{24}$O$_{41}$在低温下的比热（C$_p$）由于存在一个相当大的非磁起源的额外贡献而得到增强。 在铜位点的稀释铝掺杂或在O$_2$气氛中退火晶体显著抑制了这一特征。 使用太赫兹时域光谱技术，我们证明额外比热的出现与非常低能量（$\sim$1 meV）的禁带声子模式的存在有关，这些模式是由于相反电荷的相互非共格链和梯层之间的滑动运动产生的。 显示英文摘要

摘要： We show that low temperature specific heat (C$_p$) of the incommensurate chain-ladder system Sr$_{14}$Cu$_{24}$O$_{41}$ is enriched by the presence of a rather large excess contribution of non-magnetic origin. Diluted Al doping at the Cu site or annealing the crystal in an O$_2$ atmosphere suppresses this feature considerably. Using the THz time-domain spectroscopy, we show that the occurrence of excess specific heat is associated with the presence of very low-energy ($\sim$ 1 meV) gapped phonon modes that originate due to the sliding motion of oppositely charged mutually incommensurate chain and ladder layers.