Thickness-dependent electronic structure in layered ZrTe5 down to the two-dimensional limit

Abstract

Zirconium pentatelluride (${\mathrm{ZrTe}}_{5}$) has recently attracted intense research interest, mainly due to its potential topological nontriviality and the extraordinary quantum phenomena it displays. As an exemplary layered compound, ${\mathrm{ZrTe}}_{5}$ is expected to exhibit thickness-sensitive physical properties that vary with thinning towards the two-dimensional (2D) limit, which has not been thoroughly investigated yet. In this work, we successfully prepare sizable ${\mathrm{ZrTe}}_{5}$ thin flakes down to the monolayer for the first time. By examining the evolution of magnetotransport properties and the Shubnikov--de Haas effect in ${\mathrm{ZrTe}}_{5}$ flakes with various layer numbers, we reveal a pronounced thickness dependence of the electronic structure of ${\mathrm{ZrTe}}_{5}$ characterized by a downward shift of the Fermi level as large as \ensuremath{\sim}160 meV upon thickness reduction from bulk to two-unit cells (four atomic layers). Furthermore, an external electric field effectively modifies the magnetoresistance and quantum oscillation frequency in the few-layered ${\mathrm{ZrTe}}_{5}$. Our study proves that ${\mathrm{ZrTe}}_{5}$ thin flake can be an excellent platform for exploring the novel properties proposed for 2D topological materials as well as their tunability.