Detailed study on the Fermi surfaces of the type-II Dirac semimetallic candidates PdTe2 and PtTe2

TL;DR

This study investigates the Fermi surfaces of PdTe2 and PtTe2, revealing their high mobilities, light effective masses, and the presence of Dirac type-II nodes, with experimental results largely aligning with theoretical predictions for PdTe2.

Contribution

It provides detailed quantum oscillation measurements and compares experimental Fermi surfaces with band-structure calculations, supporting the existence of Dirac type-II nodes in PdTe2 and suggesting their probable presence in PtTe2.

Findings

PdTe2 shows excellent agreement between experiment and calculations.

PtTe2 exhibits poor agreement, indicating more complex electronic structure.

Both materials display high mobilities and light effective masses.

Abstract

We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe$_{2}$ and PtTe$_{2}$ \emph{via} the temperature and the angular dependence of the de Haas-van Alphen (dHvA) and Shubnikov-de Haas (SdH) effects. In high quality single crystals of both compounds, i.e. displaying carrier mobilities between $10^3$ and $10^4$ cm$^2$/Vs, we observed a large non-saturating magnetoresistivity (MR) which in PtTe$_2$ at a temperature $T = 1.3$ K, leads to an increase in the resistivity up to $5 \times 10^{4}$ % under a magnetic field $\mu_0 H = 62$ 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 PdTe$_{2}$ the experimentally determined Fermi surface cross-sectional areas show an excellent agreement with those resulting from band-structure calculations. Surprisingly, this is not the case for PtTe$_{2}$ whose agreement between calculations and experiments is relatively poor even when electronic correlations are included in the calculations. Therefore, our study provides a strong support for the existence of a Dirac type-II node in PdTe$_2$ and probably also for PtTe$_2$. Band structure calculations indicate that the topologically non-trivial bands of PtTe$_2$ do not cross the Fermi-level ($\varepsilon_F$). In contrast, for PdTe$_2$ the Dirac type-II cone does intersect $\varepsilon_F$, 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 the one of the Dirac type-II node. Therefore it should yield a trivial Berry-phase.