Detailed study of the Fermi surfaces of the type-II Dirac semimetallic candidates X Te 2 ( X =Pd, Pt)

Abstract

We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates ${\mathrm{PdTe}}_{2}$ and ${\mathrm{PtTe}}_{2}$ via the temperature and the angular dependence of the de Haas--van Alphen and Shubnikov--de Haas effects. In high-quality single crystals of both compounds, i.e., displaying carrier mobilities between ${10}^{3}$ and ${10}^{4}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}$/Vs, we observed a large nonsaturating magnetoresistivity which in ${\mathrm{PtTe}}_{2}$ at a temperature $T=1.3$ K leads to an increase in the resistivity up to ($5\ifmmode\times\else\texttimes\fi{}{10}^{4}$)% under a magnetic field ${\ensuremath{\mu}}_{0}H=62$ T. These high mobilities correlate with their light effective masses in the range of 0.04 to 1 bare electron mass according to our measurements. For ${\mathrm{PdTe}}_{2}$ the experimentally determined Fermi surface cross-sectional areas show excellent agreement with those resulting from band structure calculations. Surprisingly, this is not the case for ${\mathrm{PtTe}}_{2}$, whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides strong support for the existence of a Dirac type-II node in ${\mathrm{PdTe}}_{2}$ and probably also for ${\mathrm{PtTe}}_{2}$. Band structure calculations indicate that the topologically nontrivial bands of ${\mathrm{PtTe}}_{2}$ do not cross the Fermi level ${\ensuremath{\varepsilon}}_{F}$. In contrast, for ${\mathrm{PdTe}}_{2}$ the Dirac type-II cone does intersect ${\ensuremath{\varepsilon}}_{F}$, although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct ${k}_{z}$ plane with respect to that of the Dirac type-II node. Therefore, it should yield a trivial Berry phase.