Gate-tuned Aharonov-Bohm interference of surface states in a quasiballistic Dirac semimetal nanowire

Abstract

Dirac semimetals [1], such as Cd 3 As 2 or Na 3 Bi [2][3][4][5][6][7][8][9][10], show a linear electronic dispersion in three dimensions described by two copies of the Weyl equation. Applying a magnetic field can break the time reversal symmetry, and the Dirac semimetal is transformed into a Weyl semimetal with the two Weyl nodes separated in the momentum space [10,11]. Chiral charge pumping between the Weyl nodes with different chirality is predicted, which brings the Weyl fermions into the experimental realm. Recently, anomalous transport properties signaled by a pronounced negative magnetoresistance are observed as the evidence for the chiral anomaly effect [10,12].Besides this, the surface dispersion-relation of a Weyl semimetal is topologically equivalent to a non-compact Riemann surface without equal-energy contour that encloses the projection of the Weyl point [13], leading to the emergence of surface Fermi arcs [14]. Lots of angle-resolved photoemission spectroscopy (ARPES) experiments [7,[15][16][17][18] [16,19,[32][33][34][35][36][37][38]. Although the one-dimensional helical transport has been demonstrated in topological insulator nanowires through measuring the AB oscillations is the flux quantum and , where is the measured magnetic field periodicity ( in this case) and S is the cross-sectional area.From the magnetic field periodicity, we can deduce the cross-sectional area to be , which is consistent with the nanowire diameter ~58 nm. In To further clearly present the conductance oscillations, we plot the mapping of ∆G versus gate voltage and magnetic field in Fig. 1d. Clearly there are two kinds of phase modulations on the interference. One is tuned by gate voltage, and the other is influenced by the magnetic field. At a fixed gate voltage, if the conductance reaches the minimum at zero magnetic field, the conductance will be the maximum at half integer multiple of ; if the conductance is maximum at zero magnetic field, the conductance will be the maximum at integer multiple of . The phase of the AB interference is strongly dependent on gate voltage. while when the chirality is -1, the energy dispersion has a similar form with a sign 6 change. This physics picture is depicted in Fig. 2. At zero magnetic field, that is =0, the original linear energy dispersion becomes gapped with a series of sub-bands, as shown in Fig. 2a. The red and blue lines represent the chirality to be +1 and -1, respectively. According to the surface band splitting, there should emerge a periodic oscillation when the Fermi level crosses the sub-bands continuously. This is what happens in our Cd 3 As 2 nanowires, as shown in Fig. 1b.When a magnetic field is applied, the corresponding AB oscillation term should be considered. The surface energy band diagrams at the magnetic flux and are depicted in Fig. 2b, where the letter L and R denote the chirality of Weyl nodes to be +1 or −1. Apparently, when the magnetic flux is half integer of Ф 0 , the linear energy band with specified chirality emerges. The quantum transport can be...

4π -Periodic Supercurrent from Surface States in Cd3As2 Nanowire-Base

“…Because of the large surface-to-volume ratio, the contribution of surface state transport is significant and A-B oscillations are commonly observed in Cd 3 As 2 nanowires [21,22]. As mentioned before, the 4π-periodic supercurrent is closely linked with surface gapless Andreev bound states.…”

“…With nontrivial Fermi-arc surface states [8][9][10][11], Dirac semimetals have also been predicted to possess both intrinsic and extrinsic (proximity effect-induced) topological superconductivity [12][13][14][15].Cd 3 As 2 , as a stable 3D Dirac semimetal, has been identified to have unique bulk Dirac cones and nontrivial topological surface states [14,[16][17][18]. Many exotic transport properties, such as ultrahigh carrier mobility [19], chiral anomaly induced negative magnetoresistance [20], the π-Aharonov-Bohm (A-B) effect [21,22], and Weyl orbit related quantum oscillations [23,24], have been demonstrated in Cd 3 As 2 . Unconventional superconductivity has also been observed in Cd 3 As 2 through specific experiments, including the point-contact technique, high-pressure condition, etc.…”

“…The Cd 3 As 2 nanowires were synthesized via the chemical vapor deposition method, which are of high-crystal quality [20]. The nanowire has large surface-to-volume ratio and demonstrates abundant surface-related transport properties [21,22]. Synthesized Cd 3 As 2 nanowires were then transferred on silicon substrate with 285 nm-thick SiO 2 layer, which serves as a back gate to modulate the carrier density.…”

“…4(b). For the Fermi level in the valance band, the bulk related transport is restrained due to low mobility of holes, while the surface state transport is amplified in view of its high mobility, benefiting from the topologically protected Fermi Step size (nA) RF power (dBm) Step size (nA) RF power (dBm) Step size(nA) Step size(nA) Step size (nA) RF power (dBm) PHYSICAL REVIEW LETTERS 121, 237701 (2018) arcs [21,22,38]. Therefore, the significant contribution of surface state transport produces the notable 4π-periodic supercurrent, resulting in the missing of the n ¼ 1 step.…”

Observation of an Odd-Integer Quantum Hall Effect from Topological Surface States in Cd3As2

“…The three-dimensional (3D) Dirac semimetal Cd 3 As 2 has linear energy dispersion in bulk states and topologically protected surface states [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. This protection is due to the C 4 rotation symmetry that prohibits a gap near the Dirac point [1,2].…”