The realization of a spintronic device using topological insulators is not trivial, because there are inherent difficulties in achieving the surface transport regime
[1].
The majority of 3D topological insulators materials (3DTI) despite of support
helical metallic surface states on an insulating bulk, forming topological Dirac
fermions protected by the time-reversal symmetry
[2,6],
exhibit electronic scattering
channels due to the presence of residual continuous bulk states near the Dirac-point
[3].
From
ab initio calculations, we studied the microscopic origin of the
continuous bulk states in rhombohedral topological insulators materials with the
space group \(D^{5}_{3d}(R\bar{3}m)\), showing that it is possible to understand the
emergence of residual continuous bulk states near the Dirac-point into a six bands
effective model, where the breaking of the \(R_{3}\) symmetry beyond the \(\Gamma\) point
has an important role in the hybridization of the \(px\), \(py\) and \(pz\) atomic
orbitals, which leads to a band repulsion that depends on only one parameter, as shown in the figure.
Within this model, the mechanisms known to eliminate the bulk
backscattering, for instance: the stacking faults
[4],
electric field
[5]
and alloy
[7],
generated a similar effect in the effective states of the 3DTI.
Finally, we studied the surface electronic transport in the 3DTI with staking
faults, showing how the surface electronic transport is modified by perturbations of bulk.
Projected surface band structure for 20 Qls calculated using the six bands effective model varying the repulsion parameter.
The color scale is related to the contribution of the Qls in the surface.
The blue and red colors indicate the major and null contributions, respectively
Joint with
Antônio J. R. da Silva,
Instituto de Física, Universidade de São Paulo y Laboratório Nacional de Luz Síncrotron, Campinas, Brasil y A. Fazzio, Laboratório Nacional de Luz Síncrotron, Campinas, Brasil
References
[1]
L. Barreto et al.
"Surface-Dominated Transport on a Bulk Topological Insulator".
Nano Letters 14 (7 June 2014), pp. 3755-3760.
[2]
B. A. Bernevig.
Topological insulators and topological superconductors.
With Taylor L. Hughes. Princeton University Press, Princeton, NJ, 2013, pp. xii+247.
[3]
S. Kim et al.
"Surface Scattering via Bulk Continuum States in the 3D Topological Insulator Bi2Se3 ".
Phys. Rev. Lett. 107 (5 July 2011), p. 056803.
[4]
L. Seixas, L. B. Abdalla, T. M. Schmidt, A. Fazzio, and R. H. Miwa.
"Topological states ruled by stacking faults in Bi2Se3 and Bi2Te3".
Journal of Applied Physics
113.2, 023705 (2013), pages.
[5]
O. V. Yazyev, J. E. Moore, and S. G. Louie.
"Spin Polarization and Transport of Surface States in the Topological Insulators Bi2 Se3 and Bi2 Te3 from First Principles".
Phys. Rev. Lett. 105 (26 Dec. 2010), p. 266806.
[6]
H. Zhang, C.-X. Liu, X.-L. Qi, X. Dai, Z. Fang, and S.-C. Zhang.
"Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface".
Nature Physics 5 (May 2009), p. 438.
[7]
J. Zhang et al.
"Band structure engineering in (Bi1-xSbx)2Te3 ternary topological insulators".
Nature Communications 2.574 (2011).