Transport Signatures of Amorphous 3D Topological Insulator

In recent years, with the increasing potential for new solid state devices, there has been an increasing interest in exploring the transport signatures of 3D topological insulators (TIs). In particular, as longitudinal magnetic flux is varied, the conductance through 3D TI nanoribbons oscillates. These oscillations are of the Aharonov-Bohm type, i.e, with period h/e, as opposed to the Sharvin-Sharvin type oscillations with period h/2e. In the crystalline case it is known that such a sample would produce coherent oscillations and this has been demonstrated experimentally with BiSbTe3 (5) samples. It has also been shown that adding disorder to the surface of the sample preserves these oscillations (3,4). However, the extension of this result to a sample with complete geometrical/topological disorder pervading through the bulk of the sample is unknown. This is of special interest due to the relative ease of production of amorphous materials over crystalline ones and the resulting increased applicability, the most immediate example of which is the use of amorphous silicon in solar panels. Recent theoretical work has shown that topological phases can emerge in amorphous 2D systems (6). We consider here the transport signature of a finite amorphous 3D Fu-Kane-Mele type system with varying magnetic field. We construct an amorphous system with an algorithm (2) resulting in a constant coordination number for each site and employ a modified version of the Fu-Kane-Mele Hamiltonian to characterize the effects of the deviating bond angles and bonding lengths from the crystalline lattice structure. We explore the regimes under which a robust topological phase exists for this system and gauge the presence and quality of the coherent Aharanov Bohm oscillations.

1. (1) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.98.106803
   
   (2) https://www.researchgate.net/publication/334413849_Fast_algorithm_for_topologically_disordered_lattices_with_constant_coordination_number
   
   (3) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.206601
   
   (4) https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.156803
   
   (5) https://aip.scitation.org/doi/10.1063/1.5023812
   
   (6) https://arxiv.org/abs/2003.13701