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Computational Modeling of Quantum Resonances in Nanostructures

Computational Modeling of Quantum Resonances in Nanostructures. Chao-Cheng Kaun. New. engineering. science. Research Center for Applied Sciences, Acadamia Sinica, Taiwan Department of Physics, National Tsing Hua University, Taiwan. April 11, 2019 NCTU. Outline:. Introduction

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Computational Modeling of Quantum Resonances in Nanostructures

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  1. Computational Modeling of Quantum Resonances in Nanostructures Chao-Cheng Kaun New engineering science Research Center for Applied Sciences, Acadamia Sinica,Taiwan Department of Physics, National Tsing Hua University, Taiwan April 11, 2019 NCTU

  2. Outline: • Introduction 2.Conductance of single-molecule junctions Gold nanowires: Alkanedithiol, benzenedithiol, and peptide Carbon nanowires: Polyacene and graphene-nanoflake 3. Coupling in thin films Interlayer exchange coupling in Fe/Ag/Fe films Magnetic anisotropy in Fe/Ag films 4. Summary

  3. 1. Introduction: Micro-Electronics Modeling: SPICE (Simulation Program with Integrated Circuit Emphasis) Input: a schematic circuit Output: the simulated circuit behaviors. Device parameters Obtain these parameters empirically: send designs to Taiwan semiconductor foundry; make many devices; do measurements; extract parameters.

  4. Commercial TCAD tool: 1328 pages of parameter and physics descriptions

  5. The molecule-electrode coupling calculated self-consistently LUMO HOMO The charge transfer & the energy level alignment

  6. How to calculate current? 2.Conductance of single-molecule junctions Our method: Landauer formula: DFT plus non-equilibriumGreen’s functions: Taylor, Guo, Wang, PRB 63, 245407(2001); Waldron, Haney, Larade, MacDonald, Guo, PRL 96, 166804 (2006) Nanodcal (http://nanoacademic.ca/)

  7. Measured conductance: Benzenedithiol N. J. Tao et. al., Nano Lett. 4, 267 (2004)

  8. Our modeling for Alkanedithiol Gold nanowires Au (100) Au (111) D. Ugarte et. al., PRL 85, 4124 (2000) Sen & Kaun, ACS Nano, 4, 6404 (2010)

  9. Helical gold nanotubes K. Takayanagi et. al., PRL 91, 205503 (2003)

  10. Our modeling: (Unit: G0) Conductance Alkanedithiol Benzenedithiol Au (5,3) 0.0018 0.017 0.0020 0.015 Au (100) Sen, Lin & Kaun, J. Phys. Chem. C 117, 13676 (2013) Experiments0.0012 0.011 N. J. Tao et. al., JACS 128, 2135 (2006) N. J. Tao et. al., Nano Lett 4, 267 (2004)

  11. Conductance 0.0018 G0 HDT 0.017 G0 BDT Sen, Lin & Kaun, J. Phys. Chem. C 117, 13676 (2013)

  12. Peptide:

  13. Experimental data

  14. 2.

  15. Our results: Huang, Su & Kaun, ACS Omega 3, 9191 (2018)

  16. Huang, Su & Kaun, ACS Omega 3, 9191 (2018)

  17. Carbon nanowires: Polyacene Dou, Chang & Kaun, J. Phys. Chem. C 123, 4605 (2019)

  18. Graphene nanoflake Dou, Kaun & Zhang, Nanoscale 10, 4861 (2018)

  19. 3. Coupling in thin films Quantum well states (2D) Important for developing nanoscale magnetic devices!

  20. Interlayer exchange coupling in magnetic trilayers

  21. One puzzle

  22. Our calculations DFT Chang, Dou, Chen, Hong, & Kaun, Scientific Reports 5, 16844 (2015)

  23. The Fe3/Ag6/Fe3 trilayer

  24. Chang, Dou, Chen, Hong, & Kaun, ScientificReports 5, 16844 (2015)

  25. Magnetic anisotropy in ferromagnetic films

  26. The Co/Cu(001) system The Fe/Ag(001) system “No theoretical calculations available”

  27. Our calculations (comparing with experiment): Dabrowski et al.,PRL 113, 067203 (2014) DFT Chang, Dou, Guo, & Kaun, NPGAsia Materials 9, e424 (2017)

  28. Spin-orbit interaction (SOI)

  29. Controlling magnetic anisotropy electronically Chang, Dou, Guo, & Kaun, NPG Asia Materials 9, e424 (2017)

  30. 4. Sumary: Conductance of single-molecule junctions Coupling in thin films

  31. Acknowledgements: • Prof. G.-Y. Guo (National Taiwan Univ.) • Prof. T.-M. Hong (National Tsing Hua Univ.) • Prof. R. Q. Zhang (City Univ. of Hong Kong) • Former members • Prof. A. Sen (SRM Univ.) • Prof. Y.-H. Su (National Cheng Kung Univ.) • Prof. K.-P. Dou (Ocean Univ. of China) • Prof. C.-H. Chang (National Cheng Kung Univ.) • Dr. Y.-C. Chen (McGill Univ.) • C.-J. Lin • L.-W. Huang

  32. Experiment 0.011 G0

  33. Tight-binding modeling: 1.

  34. Rashba SOI field

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