Shubnikov–de Haas oscillations in bulk ZrTe5 single crystals: Evidence for a weak topological insulator

Abstract

The study of $\mathrm{ZrT}{\mathrm{e}}_{5}$ crystals is revived because of the recent theoretical prediction of topological phase in bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$. However, the current conclusions for the topological character of bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$ are quite contradictory. To resolve this puzzle, we here identify the Berry phase on both $b$- and $c$ planes of high-quality $\mathrm{ZrT}{\mathrm{e}}_{5}$ crystals by the Shubnikov--de-Hass (SdH) oscillation under tilted magnetic field at 2 K. The angle-dependent SdH oscillation frequency, both on $b$- and $c$ planes of $\mathrm{ZrT}{\mathrm{e}}_{5}$, demonstrates the two-dimensional feature. However, phase analysis of SdH verifies that a nontrivial \ensuremath{\pi}-Berry phase is observed in the $c$-plane SdH oscillation, but not in the $b$-plane one. Compared to bulk Fermi surface predicted by the first-principle calculation, the two-dimensional-like behavior of SdH oscillation measured at $b$ plane comes from the bulk electron. Based on these analyses, it is suggested that bulk $\mathrm{ZrT}{\mathrm{e}}_{5}$ at low temperature (\ensuremath{\sim}2 K) belongs to a weak topological insulator, rather than Dirac semimetal or strong topological insulator as reported previously.