Frontier orbitals of molecule systems can be modulated to tune the performance of electron/spin transport [1]. The transport phenomena in molecular devices can be understood based on density functional theory (DFT) coupled to non-equilibrium Green function theory (NEGF) [2]. Graphene nanoribbons (GNRs) can be exploited for the use of spin valves [3]. A single nucleobase interacting with the GNR via pi-pi stacking interaction [4] gives a sharp conductance change due to Fano resonance [5]. These unique resonance profiles reflect the characteristic features of frontier molecular orbitals of physisorbed molecules. The differential conductance with respect to bias and gate voltages not only distinguishes different types of nucleobases for DNA sequencing but also recognizes cancerous methylated nucleobases. This two-dimensional molecular electronics spectroscopy (2D MES) [6] could recognize single molecule signatures at atomic resolution. The advantages of the 2D MES over the one-dimensional (1D) current analysis can be comparable to those of 2D NMR over 1D NMR analysis. The GNR can be utilized as devices such as diodes and transistors. Finally, the development of attosecond spectroscopy to detect electronic motions in attosecond timescale is addressed. Using our code for real-time electron dynamics coupled to nuclear motion [7], we have investigated optical band gap, excitation energy, real time electronic motions, and Berry phase [8]. 1. W. Y. Kim et al. Acc. Chem. Res. 43, 111 (2010). 2. W. Y. Kim et al. J. Comput. Chem. 29, 1073 (2008). 3. W. Y. Kim et al. Nature Nanotech. 3, 408 (2008). 4. Y. Cho et al. Acc. Chem. Res. 47, 3321 (2014). 5. S. K. Min et al. Nature Nanotech. 6, 162 (2011). 6. A. C. Rajan et al. ACS Nano 8, 1827 (2014). 7. S. K. Min et al. J. Chem. Phys. 135, 24412 (2011). 8. S. K. Min et al. Phys. Rev. Lett. 113, 263004 (2014).

Electronic/spintronic transport, spectroscopy, and dynamics

251st National Meeting (2016)

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