Towards a better understanding of the unique ultra-low thermal conductivity in SnSe thermoelectric from constraints of its bond anharmonicit

SnSe is a new key thermoelectric material that exhibits an ultra-low lattice thermal conductivity. This is a unique phenomenon among reported TE materials; however, its origin remains highly debated. Several scenarios have been proposed among the most likely one, but not completely accepted, relates the low κT to a highly anisotropy in the phonon scattering. This may be related to the Sn–Se bond anharmonicity and anisotropy. This kind of information with a local character and dependence on the solid's vibrational properties could be only accessed by spectroscopies at local-range, as the case of EXAFS or Raman. We propose to study the bond anharmonicity and anisotropy in binary SnSe using high-quality EXAFS under isobaric condition in DAC and cryostat from 2 to 300 K at HP (100 GPa). These data will improve our knowledge on the features of the intrinsic low thermal conductivity in SnSe at non-ambient conditions and will have a high impact for further developments in thermoelectrics.