Large shift current, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>π</mml:mi></mml:math> Zak phase, and the unconventional nature of Se and Te

Recently, unconventional materials (or obstructed atomic insulators) have attracted much attention owing to the feature of mismatch between Wannier centers and positions. In this paper, we demonstrate that trigonal selenium tellurium host an nature in both electronic phonon spectra. band structures, representation (BR) decomposition for occupied bands has contain essential BR $A@3b$, real-space invariant is $\delta_1@3b=-1$. The $\pi$ Zak phase suggests one-dimensional Se/Te chain a chiral Su-Schrieffer-Heeger chain. effective magnetism can be induced by $p$ states at ends. More importantly, large shift current obtained Se quantum well. addtion, spectra, three sets are well separated assigned $B@3b$, $B@3a$, $A@3b$ BRs, respectively. Thus, predicted on (0001) surface. As prototypes our findings could create interest study surface these novel materials.