Quantum oscillations and nontrivial topological state in a compensated semimetal TaP2

Abstract

topological insulator with the Z 2 indices of (0; 111), which exhibits topological surface states on the (001) surface.

Nontrivial topological states in the tantalum dipnictides TaX2 (X = As, P)

“…TaAs 2 crystal is usually grown using the chemical vapor transfer (CVT) method, which could be optimized via changing the transfer agent or growth time, thus yielding crystals with the size even larger than 2 mm, as seen in Fig. 1a [28,30,32]. In such a technique, the chemicals Ta (99.9%, Aladdin Chemicals, China) and As (99.999%, Alfa Chemicals, the United States) were mixed in a molar ratio of 1:2 and were placed into an Al 2 O 3 crucible.…”

“…The TaP 2 single crystal can also be grown by the CVT method, but it is needle-like with the length of only several hundred microns, which cannot meet the requirements for further characterizations. We, therefore, alternatively used the flux method to grow the crystal [28] by mixing the starting materials tantalum (99.9%, Aladdin Chemicals, China), phosphorus (99.9%, Aladdin Chemicals, China), and tellurium (99.9%, Aladdin Chemicals, China) in a molar ratio of 1:2:20 and placing the mixture into an alumina crucible. The crucible was sealed into a quartz tube under the vacuum of 10 -4 Pa and was then slowly heated up to 1000 °C within 20 h. After reacting for 20 h, the assembly was slowly cooled down to 600 °C at a temperature decreasing rate of 2-3 °C•h −1 .…”

“…The magneto-transport properties of TaP 2 had not been ever investigated before our work [28], because TaP 2 was not available at that time. The magneto-transport measurement results on TaP 2 crystals are presented in Fig.…”

“…The exciting discovery has arrested worldwide vast attentions on the exploration of new WSMs, which has expanded the family of materials with a considerable number very fast. Unlike the non-centrosymmetry crystal structure of TaAs, the tantalum dipnictide TaX 2 (X = As, P) crystallize in the monoclinic structure with a space group C2/m, which is centrosymmetric [27,28]. In such centrosymmetric nonmagnetic materials, the presence of both SI and TR symmetries only allows the formation of DPs, whereas WPs are not possible unless any one or both symmetries could be broken [29].…”

“…In such centrosymmetric nonmagnetic materials, the presence of both SI and TR symmetries only allows the formation of DPs, whereas WPs are not possible unless any one or both symmetries could be broken [29]. In the last several years, TaAs 2 and TaP 2 have gained a lot of attentions primarily owing to their extremely large magnetoresistance (XMR) as well as the n-LMR [27,28,[30][31][32]. The XMR, which has potential applications in magneto-electronic devices, can even exceed 1.2 × 10 6 % at the magnetic field B = 9 T and the temperature T = 2 K. It is attributed to their nearly perfectly compensated electrons and holes carriers according to both band-structure calculations and ARPES measurements.…”