Low-temperature heat capacity of Sr 8 Ga 16 Ge 30 and Ba 8 Ga 16 Ge 30 : Tunneling states and electron-phonon interaction in clathrates
Low-temperature heat capacity of Sr 8 Ga 16 Ge 30 and Ba 8 Ga 16 Ge 30 : Tunneling states and electron-phonon interaction in clathrates
复制标题
DOI：
10.1103/physrevb.82.085206
复制
发表时间：
2010-08
影响因子：
3.7
通讯作者：
Jingtao Xu;Jun Tang;Kazumi Sato;Y. Tanabe;H. Miyasaka;M. Yamashita;S. Heguri;K. Tanigaki
中科院分区：
文献类型：
--
作者：
Jingtao Xu;Jun Tang;Kazumi Sato;Y. Tanabe;H. Miyasaka;M. Yamashita;S. Heguri;K. Tanigaki
Tunneling states of ${\text{Sr}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$ (SGG) and ${\text{Ba}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$ (BGG) are studied in detail using single crystals with a variety of carrier concentrations from the view point of heat capacity $({C}_{p})$. An important excessive contribution $\ensuremath{\alpha}T$ due to the tunneling states is found besides ${\ensuremath{\gamma}}_{e}T$ of the conduction electrons. The value of $\ensuremath{\alpha}$ is accurately deduced to be $10.1\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{mJ}/\text{mol}\text{ }{\text{K}}^{2}$ for SGG while such a value is as small as $0.8\ifmmode\pm\else\textpm\fi{}0.4\text{ }\text{mJ}/\text{mol}\text{ }{\text{K}}^{2}$ for BGG. From the temperature evolution of ${C}_{p}$ as a function of carrier concentration, the effective masses, one of the most important physical parameters for evaluating electron-phonon interactions ${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}ph}$, are accurately estimated to be $1.68{m}_{0}$ and $1.01{m}_{0}$ for SGG and BGG, respectively. The ${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}ph}$ seems to be enhanced when the anharmonic rattling modes are involved.
Tunneling states of ${\text{Sr}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$ (SGG) and ${\text{Ba}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$ (BGG) are studied in detail using single crystals with a variety of carrier concentrations from the view point of heat capacity $({C}_{p})$. An important excessive contribution $\ensuremath{\alpha}T$ due to the tunneling states is found besides ${\ensuremath{\gamma}}_{e}T$ of the conduction electrons. The value of $\ensuremath{\alpha}$ is accurately deduced to be $10.1\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{mJ}/\text{mol}\text{ }{\text{K}}^{2}$ for SGG while such a value is as small as $0.8\ifmmode\pm\else\textpm\fi{}0.4\text{ }\text{mJ}/\text{mol}\text{ }{\text{K}}^{2}$ for BGG. From the temperature evolution of ${C}_{p}$ as a function of carrier concentration, the effective masses, one of the most important physical parameters for evaluating electron-phonon interactions ${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}ph}$, are accurately estimated to be $1.68{m}_{0}$ and $1.01{m}_{0}$ for SGG and BGG, respectively. The ${\ensuremath{\lambda}}_{e\text{\ensuremath{-}}ph}$ seems to be enhanced when the anharmonic rattling modes are involved.