Electronic conductance via atomic wires: a phase field matching theory approach

Abstract

A model is presented for the quantum transport of electrons, across finite atomic wire nanojunctions between electric leads, at zero bias limit. In order to derive the appropriate transmission and reflection spectra, familiar in the Landauer-Büttiker formalism, we develop the algebraic phase field matching theory (PFMT). In particular, we apply our model calculations to determine the electronic conductance for freely suspended monatomic linear sodium wires (MLNaW) between leads of the same element, and for the diatomic copper-cobalt wires (DLCuCoW) between copper leads on a Cu(111) substrate. Calculations for the MLNaW system confirm the correctness and functionality of our PFMT approach. We present novel transmission spectra for this system, and show that its transport properties exhibit the conductance oscillations for the odd-and even-number wires in agreement with previously reported first-principle results. The numerical calculations for the DLCuCoW wire nanojunctions are motivated by the stability of these systems at low temperatures. Our results for the transmission spectra yield for this system, at its Fermi energy, a monotonic exponential decay of the conductance with increasing wire length of the Cu-Co pairs. This is a cumulative effect which is discussed in detail in the present work, and may prove useful for applications in nanocircuits. Furthermore, our PFMT formalism can be considered as a compact and efficient tool for the study of the electronic quantum transport for a wide range of nanomaterial wire systems. It provides a trade-off in computational efficiency and predictive capability as compared to slower first-principle based methods, and has the potential to treat the conductance properties of more complex molecular nanojunctions.PACS number(s): 73.63. Nm, 03.65.Fd, 31.15.xf

The increase in conductance of a gold single atom chain during elastic elongation

“…7,25 After the formation of the SAC, small fluctuations (%15%) in the conductance were experimentally observed during elongation. 7 Several theoretical studies 21,28,29 demonstrated that these fluctuations occur when a single gold atom transitions from the 2D part of the nanowire to the SAC. This movement increases the number of atoms in the SAC by one and changes its state from even to odd and vice versa.…”

“…This movement increases the number of atoms in the SAC by one and changes its state from even to odd and vice versa. It was found 28 that these states have different transmission spectra that make the conductance higher for odd numbers of atoms in the SAC and lower for even numbers. Another effect that has been satisfactorily explained is the gradual decrease of conductivity within a "plateau" during elastic elongation, which has been attributed to bond stretching.…”

“…For the conductance calculations, we elongated chains of different lengths and investigated the corresponding changes in the conductance. It is well known 21,28,29 that odd-even oscillations in the conductance are observed as the number of atoms in the SAC increases. However, in this work, the primary interest is in how the conductance increases with elastic elongation, and this effect occurs equally for all chain lengths.…”

Quantum conductance of silicon-doped carbon wire nanojunctions

“…In the present work we investigate the electronic scattering processes on the basis of the phase field matching theory (PFMT) [53], [54], originally developed for the scattering of phonons and magnons in nanostructures [55], [56], [57], [58], [59]. Our theoretical method is based on the appropriate phase matching of the Bloch states of ideal leads to the local states in the scattering region.…”

“…Our theoretical method is based on the appropriate phase matching of the Bloch states of ideal leads to the local states in the scattering region. In this approach the electronic properties of the system are described in the framework of the tight-binding formalism (TB) which is widely exploited for electronic transport calculations [54], [60], [61], [62], [63], and for simulating the STM images of nanostructures [64], [65]. In particular, we employ the appropriate Slater-Koster [66] type Hamiltonian parameters calculated on the basis of the Harrison tight-binding theory (HTBT) [67].…”