Topological insulator-metal transition and molecular electronics device based on zigzag phagraphene nanoribbon

Abstract

In this work, we investigate the electronic transport properties of a graphene allotrope composed of 5–6-7 carbon aromatic rings called phagraphene and compare with the results of the transition-voltage spectroscopy (TVS) and propose the behavior at low voltage characteristic of a topological insulator. Phagraphene properties were compared to those of graphene in a zigzag nanoribbon configuration, zigzag graphene vs zigzag phagraphene nanoribbon (zzGNR and zzPGNR). The molecular geometry and the electronic properties were calculated by density functional theory (DFT) without spin, and the electronic transport and TVS were obtained by means of DFT combined with non-equilibrium Green´s function when we couple the optimized geometry of zzGNR and zzPGNR to the leads (left and right), forming the molecular junction that will be subjected to the action of an external bias voltage (Ve) to generate the molecular device. The results exhibit (i) a metal-insulator transition when Ve is increased until Ve = 1.4 V which corresponds to the nonlinear region (resonance), showing the field effect transistor behaviour for zzGNR junctions; and (ii) two nonlinear regions (two negative differential resistances), showing a resonant tunnel diode behaviour with two operation windows (Ve = 0.5 V and Ve = 1.7 V) for the zzPGNR junction. In addition, the zzPGNR junction exhibits topological insulator characteristics upon introducing topological defects such as pentagons and heptagons in the hexagonal lattice of graphene, and when Ve = 1.7 V, there occurs a topological insulator-metal transition that can be seen in the behaviour of the density of states, transmittance, and frontier molecular orbitals with Ve.

Electronic, optical, vibrational and thermodynamic properties of phaBN structure: a first principles study

“…This flat carbon allotrope is energetically comparable to graphene and more favorable than other carbon allotropes Email address: jonas.lima@ufrpe.br (Jonas R. F. Lima) proposed in previous works due to its hybridization in sp 2 . Since its proposal, phagraphene attracted great deal of attention, which can be confirmed by the number of works addressed to this subject [20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36].…”

Topological phase transition associated with structural phase transition in ternary half Heusler compound LiAuBi

“…The discovery of a novel quantum state of matter having bulk band gap but conducting surface states led to the introduction of topological insulators (TIs) in the condensed matter physics [1][2][3][4][5][6][7]. The observation of unique property of TIs forbid the backscattering of electrons under zero magnetic field received strong attention from the community of spintronics and quantum computing [8][9][10][11].…”

Strain effect on topological and thermoelectric properties of half Heusler compounds XPtS (X = Sr, Ba)

“…In recent years, the topological insulators (TIs) and topological semi-metals (TSMs) has gathered considerable recognition in the fields of condensed matter physics [1][2][3][4]. The bulk band gap and topologically protected conducting surface states in non-trivial insulators (TIs) makes them a unique quantum state of matter which has potentials in spintronics, nanoelectronics, and many more [5,6].…”