Dr. Yong-Hoon Kim is an associate professor of School of Electrical Engineering at Korea Advanced Institute of Science and Technology (KAIST). He received the B.S. (1995) at Seoul National University, and the Ph.D. (2000) at University of Illinois at Urbana-Champaign. He was a Humboldt Fellow at Technische Universität München from 2000 and 2002, and a postdoctoral researcher at California Institute of Technology from 2002 to 2004. In 2004, he returned to Korea as an assistant professor at Korea Institute for Advanced Study, and since then affiliated with University of Seoul from 2006 to 2010 and with KAIST since 2010. Dr. Kim is an author of more than 80 peer-reviewed journal papers (H-index: 27, number of citations: > 2,450, according to Google Scholar), and has been awarded multiple awards including Research Innovation Minister Award at Nano Korea 2017. His research interests are mainly on the development of first-principles calculation approaches for nonequilibrium open quantum systems and their applications to nanodevices based on functional low-dimensional materials.

Electrified Electrochemical Interfaces from a Quantum Transport Viewpoint

Prof. Yong-Hoon Kim

School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea

In the effort to develop advanced energy and electronic devices based on novel low-dimensional materials, first-principles or ab initio simulations are playing an increasingly important role by providing atomistic information that are not easily accessible in experiments. In this respect, a key ingredient that is still immature and should be further developed is the capability to treat non-equilibrium open junction systems under finite bias in a first-principles manner. For example, for graphene electrode-based van der Waals 2D tunneling transistors, ab initio simulations are currently not possible due to the inherent limitations of the standard approach combining density functional theory (DFT) and non-equilibrium Green’s function (NEGF) formalisms [1-2]. In this talk, I will discuss the formulation and applications of the multi-space constrained-search DFT (MS-DFT) formalism we have been developing at KAIST for the past decade or so [1-4]. Seeking an alternative to the standard Landauer picture for quantum transport, we first propose a viewpoint that maps quantum transport processes to space-resolved (drain-to-source) optical excitation counterparts. The multi-space excitation picture for quantum transport then allows the formulation of microcanonical approaches for quantum transport, and the resulting MS-DFT provides unique opportunities in understanding and designing nanoscale devices in operando conditions. For example, unlike in the grand-canonical DFT-NEGF, the non-equilibrium total energy as well as quasi-Fermi level or voltage drop profile information can be obtained within the microcanonical MS-DFT [3,4]. As an appropriate thermodynamic potential for biased electrode/channel interfaces, I then establish the concept of electric enthalpy of formation. Key initial results obtained for electrified water/electrode interfaces will be outlined [5].

[1] H. S. Kim & Kim, Y.-H. “Constrained-search density functional study of quantum transport in two-dimensional vertical heterostructures”, arXiv:1808.03608 [cond-mat.mes-hall] (2018).

[3] T. H. Kim, J. Lee, R. Lee, & Y.-H. Kim, “Gate-versus defect-induced voltage drop and negative differential resistance in vertical graphene heterostructures”. Npj Comput. Mater. 8, 50 (2022).

[3] J. Lee, H. S. Kim, and Y.-H. Kim, "Multi-space excitation as an alternative to the Landauer picture for non-equilibrium quantum transport", Adv. Sci. 7, 2001038 (2020).

[4] J. Lee, H. Yeo, and Y.-H. Kim, "Quasi-Fermi level splitting in nanoscale junctions from ab initio", Proc. Natl. Acad. Sci. U. S. A. 117, 10142 (2020)

[5] J. Lee and Y.-H. Kim, “First-principles study of the hydrogen-bonding network in water at the biased electrode interface”, Bull. Amer. Phys. Soc. 65, F45.00006 (2020)