Detailed study of the Fermi surfaces of the type-II Dirac semimetallic candidates XTe2 ( X =Pd, Pt)

Abstract

We present a detailed quantum oscillatory study on the Dirac type-II semimetallic candidates PdTe2 and PtTe2 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 PtTe2 at a temperature T = 1.3 K, leads to an increase in the resistivity up to 5 × 10 4 % under a magnetic field µ0H = 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 PdTe2 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 PtTe2 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 PdTe2 and probably also for PtTe2. Band structure calculations indicate that the topologically non-trivial bands of PtTe2 do not cross the Fermi-level (εF). In contrast, for PdTe2 the Dirac type-II cone does intersect εF , although our calculations also indicate that the associated cyclotron orbit on the Fermi surface is located in a distinct kz plane with respect to the one of the Dirac type-II node. Therefore it should yield a trivial Berry-phase.

Topological Type-II Dirac Fermions Approaching the Fermi Level in a Transition Metal Dichalcogenide NiTe2

“…More recently, the transition metal dichalcogenides (TMDs) TMX 2 (TM=Pd, Pt; X=Se, Te) were proposed to host type-II Dirac fermions and were soon verified in angle-resolved photoemission spectroscopy (ARPES) experiments. [17][18][19][20][21][22][23][24][25][26][27][28] Interestingly, PdTe 2 also superconducts below T c =2 K and the Au substitution can boost T c to a maximum value of 4.7 K, making this family of TMDs a promising platform to search for topological superconductors. [29][30][31][32][33][34] However, the Dirac points reported in these materials are located deeply below the Fermi level, with a binding energy of 0.6 eV in PdTe 2 , 0.8 eV in PtTe 2 , and 1.2 eV in PtSe 2 .…”

Single full gap with mixed type-I and type-II superconductivity on surface of the type-II Dirac semimetal PdTe2 by point-contact spectroscopy

“…Recently, the transition-metal dichalcogenide compound PdTe 2 has been confirmed to be a type-II Dirac semimetal with a tilted Dirac cone below the Fermi energy by the angle resolved photoemission spectroscopy (ARPES) and there exists a spin-polarized topological surface state [29,30]. De Haas-van Alphen (dHvA) experiments also evidence the nontrivial Berry phase for one of the Fermi-surface pockets, probably a hole pocket from the tilted Dirac cone [31,32]. On the other hand, superconductivity in PdTe 2 with a transition temperature T c ∼ 1.7 K has been known for a long time, serving as a promising candidate for stoichiometric TSCs [33].…”

Anomalous charge transport of superconducting Cu$_{x}$PdTe$_2$ under high pressure

“…relating the frequency F of the quantum oscillations to the extremal Fermi surface area normal to the magnetic field, A(E F ), we estimate A(E F ) and, consequently, k F . Assuming circular cross sections of the Fermi surface, SdH and dHvA measurements [11,15,19] unveil a low frequency at ∼ 8 T, a group of medium frequencies in the 110 T < F < 140 T range and a high frequency of ∼450 T corresponding to k F values of 0.016, 0.057 -0.062 and 0.12 Å −1 , respectively. Evidently, these values are small as compared to the size of the first BZ, so the model of acoustic phononlimited scattering is applicable.…”

“…On one hand, the existence of type-II Dirac cones have been predicted by ab initio calculations and confirmed experimentally by angle resolved photoemission spectroscopy (ARPES) and by Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) quantum oscillations. The latter measurements further indicate that PdTe 2 is a multi-band semimetal with a nontrivial Berry phase for one of these bands [11,15,19]. On the other hand, scanning tunneling microscopy and spectroscopy studies [20][21][22] support a picture of conventional BCS superconductivity contrasting the scenario of topological states at the Fermi surface.…”