Intermetallic clathrates are materials characterized by a large cage structure where guest atoms can move anharmonically,providing these materials exotic thermoelectric properties.Unfortunately,the dynamical and atomi...Intermetallic clathrates are materials characterized by a large cage structure where guest atoms can move anharmonically,providing these materials exotic thermoelectric properties.Unfortunately,the dynamical and atomic nature of the rattling phonons,and their interactions with the electronic structure,are not fully understood.Here,we report that a germanium isotope effect can trigger an inherent guest rattling and cage distortion in clathrate Ba8Ga16Ge30(BGG).Raman-scattering spectroscopy and advanced electron microscopy demonstrate that the atomic germanium isotope effect induces an offcentre rattling at the 6d sites as well as a tetrakaidecahedron deformation which is anisotropic for ntype BGG but isotropic for p-type BGG.The present findings indicate that the large n-type germanium isotope effect arises from the strong electron-phonon coupling,which opens up a novel avenue for manipulating dynamical motions of phonons via atomic isotope engineering.展开更多
基金National Natural Science Foundation of China(NSFC)(grant no.11274234)R.A.thanks the financial supports from NSFC(grant no.51771126)+4 种基金Youth Foundation of Science&Technology Department of Sichuan Province(grant no.2016JQ0051)Sichuan University Talent Introduction Research Funding(grant no.YJ201537)Sichuan University Outstanding Young Scholars Research Funding(grant no.2015SCU04A20)P.R.and S.-F.W.acknowledge support from NSFC(grant nos.11274362 and 11674371)the Ministry of Science and Technology of China(grant nos.2015CB921000,2016YFA0401000 and 2016YFA0300300).J.T.thank Xiangjun Wei and Xiaolong Li for their useful discussion on PXRD data.
文摘Intermetallic clathrates are materials characterized by a large cage structure where guest atoms can move anharmonically,providing these materials exotic thermoelectric properties.Unfortunately,the dynamical and atomic nature of the rattling phonons,and their interactions with the electronic structure,are not fully understood.Here,we report that a germanium isotope effect can trigger an inherent guest rattling and cage distortion in clathrate Ba8Ga16Ge30(BGG).Raman-scattering spectroscopy and advanced electron microscopy demonstrate that the atomic germanium isotope effect induces an offcentre rattling at the 6d sites as well as a tetrakaidecahedron deformation which is anisotropic for ntype BGG but isotropic for p-type BGG.The present findings indicate that the large n-type germanium isotope effect arises from the strong electron-phonon coupling,which opens up a novel avenue for manipulating dynamical motions of phonons via atomic isotope engineering.
