T-square resistivity without Umklapp scattering in dilute metallic Bi<sub>2</sub>O<sub>2</sub>Se.

Wang, Jialu; Wu, Jing; Wang, Tao; Xu, Zhuokai; Wu, Jifeng; Hu, Wanghua; Ren, Zhi; Liu, Shi et al. · Nat Commun · 2020

basic_science · Level V

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Abstract

Fermi liquids (FLs) display a quadratic temperature (T) dependent resistivity. This can be caused by electron-electron (e-e) scattering in presence of inter-band or Umklapp scattering. However, dilute metallic SrTiO<sub>3</sub> was found to display T<sup>2</sup> resistivity in absence of either of the two mechanisms. The presence of soft phonons as possible scattering centers raised the suspicion that T<sup>2</sup> resistivity is not due to e-e scattering. Here, we present the case of Bi<sub>2</sub>O<sub>2</sub>Se, a layered semiconductor with hard phonons, which becomes a dilute metal with a small single-component Fermi surface upon doping. It displays T<sup>2</sup> resistivity well below the degeneracy temperature in absence of Umklapp and inter-band scattering. We observe a universal scaling between the T<sup>2</sup> resistivity prefactor (A) and the Fermi energy (E<sub>F</sub>), an extension of the Kadowaki-Woods plot to dilute metals. Our results imply the absence of a satisfactory understanding of the ubiquity of e-e T<sup>2</sup> resistivity in FLs.