Yu-Jie Hao

TL;DR: The temperature-dependent interplay of three separate electronic bands in hole-doped tin sulfide (SnS) crystals leads to synergistic optimization between effective mass and carrier mobility and can be boosted through introducing selenium (Se), enhancing the power factor and lowering the thermal conductivity after Se alloying.

TL;DR: A topological insulator with magnetic elements shows surprising conductive behavior on its surface, presenting either a hurdle to realizing exotic quantum phenomena or a boon to devices with new charge transport mechanisms as mentioned in this paper.

TL;DR: In this paper, a gapless Dirac cone at the (0001) surface of MnBi$_2$Te$_4$ exists between the bulk band gap and the surface state remains unchanged across the bulk Neel temperature, and is even robust against severe surface degradation.

Abstract: Tin selenide (SnSe), a simple binary compound with low-cost, earth-abundant and eco-friendly elements, has aroused extensive interest in the thermoelectric community on account of its promising power generation. Herein, we report a much more advantageous SnS crystal with promising thermoelectric performance, as an alternative to SnSe. We found that the maximum ZT > 1.0 at 873 K and high device ZT (ZTdev) > 0.57 from 300 to 873 K can be achieved in hole-doped SnS crystals, projecting a conversion efficiency of ∼10.4%. We attribute the excellent performance of SnS to its remarkable electron and phonon band structures. SnS possesses multiple valence bands, which can be activated by hole doping through pushing the Fermi level deep into the valence band structure, and activating several Fermi pockets to produce enhanced Seebeck coefficients and high power factors ∼30 μW cm−1 K−2 at 300 K. Meanwhile, the anharmonic and anisotropic bonding of SnS leads to a low thermal conductivity, which ranges from 0.65 to 0.85 W m−1 K−1 at 873 K. Our results indicate that SnS is a promising thermoelectric material for energy conversion applications in low and moderate temperature ranges.

TL;DR: In this paper, it was shown that unusual surface behavior at the terminations of a recently discovered magnetic topological insulator depends on the interplay between different building blocks within the material.