Two-Carrier Transport Induced Hall Anomaly and Large Tunable Magnetoresistance in Dirac Semimetal Cd₃As₂ Nanoplates

Abstract

Cd 3 As 2 is a model material of Dirac semimetal with a linear dispersion relation along all three directions in the momentum space. The unique band structure of Cd 3 As 2 makes it with both Dirac and topological properties. It can be driven into a Weyl semimetal by the symmetry breaking or a topological insulator by enhancing the spin-orbit coupling. Here we report the temperature and gate voltage dependent magnetotransport properties of Cd 3 As 2 nanoplates with Fermi level near the Dirac point. The Hall anomaly demonstrates the two-carrier transport accompanied by a transition from n-type to p-type conduction with decreasing temperature. The carrier-type transition is explained by considering the temperature dependent spin-orbit coupling. The magnetoresistance exhibits a large non-saturating value up to 2000% at high temperatures, which is ascribed to the electron-hole compensation in the system. Our results are valuable for understanding the experimental observations related to the two-carrier transport in Dirac/Weyl semimetals, such as Na 3 Bi, ZrTe 5 , TaAs, NbAs, and HfTe 5 .KEYWORDS: Dirac semimetal, magnetoresistance, two-band transport, temperature dependence, Hall resistance Three-dimensional (3D) Dirac semimetal 1-3 is a quantum material, where the conduction bands and valence bands touch at discrete points, known as Dirac points.In momentum space, it has linear dispersion along all three directions near the Dirac points, which are protected by the rotational crystalline symmetry. 3,4 Upon breaking of time-reversal symmetry or spatial inversion symmetry, the Dirac point splits into a pair of Weyl nodes with opposite chiralities, thus the Dirac semimetal changes into Weyl semimetal. 5,6 The distinct electronic structures of Dirac semimetal give rise to many other topological phases, for examples, topological insulator 7,8 and topological superconductor. 9 Recently, the negative magnetoresistance (MR) has been observed in Dirac semimetal 10-13 and Weyl semimetal, 14 which is attributed to the chiral anomaly in the presence of parallel electric field and magnetic field. 15,16 In the family of 3D Dirac semimetal, Cd 3 As 2 is a model material that has a pair of Dirac points near the Γ point in the Brillouin zone. 3,[17][18][19] Angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy both reveal the linear dispersion near the Dirac ResultsNanoplate Characterizations. The as-grown Cd 3 As 2 nanoplates are single crystalline. 31 As shown in Figure 1a, the scanning electron microscopy (SEM) image indicates that the lateral dimension of the nanoplates ranges from several micrometers to tens of micrometers. A corner of a typical nanoplate is shown by the transmission electron microscopy (TEM) image in Figure 1b. The high-resolution TEM image in Si substrate with 285 nm SiO 2 thin layer serves as the back gate. Figure 2b shows the temperature dependence of the longitudinal resistivity, which exhibits a semiconducting behavior at high temperatures and a metallic behavi...

Charge Transfer and Built-in Electric Fields between a Crystalline Oxide and Silicon

“…The non-linear behavior and crossover in sign of Rxy are consistent with the emergence of parallel conduction from a hole-gas in the silicon near the interface. To quantify the sheet density and mobility of the hole-gas, we analyze the Rxy data using a 2-carrier model that is parameterized by the sheet carrier densities nh , ne and mobilities µh, µe of the hole and electron carriers in the Si and SNTO, respectively (see Supporting Information) [15]. observed for the x = 0.20 heterojunction at T > 320 K. An average µh of ~ 500 cm 2 V -1 s -1 is derived from the fits for the heterojunctions that exhibit a hole gas, which is consistent with the bulk hole mobility of Si.…”

Ultrafast relaxation dynamics of photoexcited Dirac fermions in the three-dimensional Dirac semimetalCd3As2

“…Cd3As2 nanoplates were synthesized from Cd3As2 powders (Alfa Aesar 99.99% purity) by chemical vapor deposition with a silicon substrate placed at downstream to collect the products [38,[60][61][62]. Before the growth, the system was flushed several times with Argon gas to thoroughly remove the oxygen in the tube.…”

Dirac Semimetal Heterostructures: 3D Cd3As2 on 2D Graphene

“…A typical HRTEM image shown in Figure a demonstrates the single crystalline nature of the Cd 3 As 2 nanoplates. The selected area electron diffraction (SAED) pattern (see the inset of Figure a) shows the crystal planes of tetragonal structure (space group: I4 1 /acd ), and indicates the hexagonal symmetry of the (112) surface plane . According to our previous work, the Cd 3 As 2 nanoplates show electron mobility ≈1.3 × 10 4 cm 2 V −1 s −1 and hole mobility ≈9 × 10 2 cm 2 V −1 s −1 at 1.5 K .…”

“…The Cd 3 As 2 nanoplates were synthesized by chemical vapor deposition method with the thickness ranging from 200 to 700 nm . The nanoplates are with high crystal quality as characterized by statistic high‐resolution transmission electron microscopy (HRTEM) analysis of more than 50 samples.…”