Lysine based dipeptides-molecular rectifiers with very high rectification ratio and their application towards designing logic gates

Abstract

In this research paper, we have enquired the dipeptides (i.e., smallest peptides) consisting of oppositely charged amino acids namely, Lysine-Aspartic and Lysine-Glutamic, where l-Lysine is positively charged, and both L-Aspartic and L-Glutamic are negatively charged amino acids. The l-Glutamic acid has only one extra CH2 chain as compared with l-Aspartic acid. These two dipeptides are stringed to Au, Ag and Cu electrodes, to form molecular devices. Distinct parameters including conductance, Homo-Lumo gap, dipole moment, current-voltage characteristics are intrigued using NEGF-DFT technique. Au-Lysine-Aspartic-Au offers the negative differential resistance regime with the highest peak-to-valley current ratio of 28.79. Lysine-Aspartic with Cu electrodes and Lysine-Glutamic with Au electrodes offers the highest rectification ratio of 146.96 and 34.31 respectively, as compared with other electrodes. Lysine-Aspartic based dipeptides offer higher rectification ratio as compared with Lysine-Glutamic based dipeptides. Moreover, these two dipeptides offer opposite correlation between dipole moment, coupling strength and switching regimes. The reason behind rectification ratio and negative differential resistance is elaborated using transmission spectra, molecular projected self-Hamiltonian states and transmission pathway. The OR, AND and XOR logic gates are proposed using switching regimes of Au-Lysine-Aspartic-Au. We have also detected the thermal stability of one of the heterostructure using ab initio molecular dynamics simulation.