Unmasking the Hidden Doping Mechanisms in Misfit TMD Heterostructures—ARPES and Ab Initio Prediction of Incommensurate Electronic Structure Without Artificial Strain

Misfit heterostructures, such as (LaSe)_1.14(NbSe₂)₂, have been proposed as platforms for realizing heavily doped two-dimensional transition-metal-dichalcogenide (TMD) layers [1,2], which exhibit exotic quantum phases [2,3], including Ising superconductivity [4]. Despite significant interest, the existence, extent, and nature of TMD doping in these materials has been a subject of contention [5], with many attributing the doping to an interlayer charge transfer. Although theoretical tools like density functional theory (DFT) are typically equipped to address these problems, the incommensurate nature of these misfit heterostructures hinders the use of conventional <i>ab initio </i>techniques. In this presentation, we extend Mismatched Interface Theory (MINT) [6] from single two-dimensional interfaces to three-dimensional layered heterostructures (MINT-Sandwich). This new approach allows us to perform <i>ab initio</i> studies on the misfits without introducing the artificial strain present in previous techniques.<br/><br/>With our novel approach, we accurately predict the interlayer charge transfer in the misfit compound (LaSe)_1.14(NbSe₂)₂. We further predict the incommensurate electronic structure, from which we extract the effective doping of the Fermi-level crossing bands. The excellent agreement between our <i>ab initio</i> predictions and angle-resolved photoemission spectroscopy (ARPES) measurements indicates that our novel MINT-Sandwich approach provides a highly accurate understanding of the electronic structure and the detailed charge transfer processes in this incommensurate material.<br/><br/>Our results conclusively demonstrate, contrary to prior expectation, that the interlayer charge transfer and effective doping in (LaSe)_1.14(NbSe₂)₂ differ by an order of magnitude. Through careful analysis of band hybridization and energy-resolved electron densities, we find that the formation of interlayer covalent bonds creates a net polarization between the layers, ultimately driving the observed effective doping. By interpreting this effective doping in terms of a <i>polarized</i> quantum capacitor model, we extend this insight towards the rational design of heavily doped heterostructures beyond the misfits. We then further discuss the use of our method in the calculation of electron-phonon linewidths and superconducting critical temperatures in incommensurate and twisted heterostructures.<br/><br/><b>This work made use of the</b><b> </b><b>Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM), which is supported by the National Science Foundation under Cooperative Agreement No. DMR-2039380.</b><br/><br/>[1] R. Leriche, A. Palacio-Morales, M. Campetella, C. Tresca, S. Sasaki, C. Brun, F. Debontridder, P. David, I. Arfaoui, and O. Šofranko, Advanced Functional Materials 31, 2007706 (2021).<br/>[2] N. Ng and T. McQueen, APL Materials 10, 100901 (2022).<br/>[3] S. Manzeli, D. Ovchinnikov, D. Pasquier, O. V. Yazyev, and A. Kis, Nature Reviews Materials 2, 17033 (2017).<br/>[4] B. T. Zhou, N. F. Q. Yuan, H.-L. Jiang, and K. T. Law, Phys. Rev. B 93, 180501 (2016), publisher: American Physical Society.<br/>[5] F. Göhler, G. Mitchson, M. B. Alemayehu, F. Speck, M. Wanke, D. C. Johnson, and T. Seyller, Journal of Physics: Condensed Matter 30, 055001 (2018), publisher: IOP Publishing<br/>[6] E. Gerber, Y. Yao, T. Arias, and E.-A. Kim, Physical Review Letters 124, 106804 (2020).