ES22-Lopez-Morales

Author: López-Morales, Gabriel I.
a. Department of Physics, City College of the City University of New York, New York, NY;
b. Department of Chemistry, Lehman College of the City University of New York, Bronx, NY;
c. The Graduate Center of the City University of New York, New York, NY

Title: Density functional theory and quantum embedding studies of Er3+ in WS2

Abstract: Single photon emitters in the form of rare-earth (RE) impurities are being actively explored as solid-state spin-qubits, largely due to their electronically screened 4f states that result in hours-long coherence lifetimes and, as in the case of Er3+, homogeneous linewidths as narrow as 50 Hz within the telecom band. Harnessing the intrinsic potential of Er3+ and other REs, however, relies on finding suitable host materials that avoid unwanted decoherences in the form of strain and/or hyperfine interactions, while being easily integrated with current device technology. An interesting alternative along these lines is monolayer tungsten disulfide (WS2), a low spin-active nuclei transition metal dichalcogenide (TMD) with a bandgap of ~2.1 eV and sizable lattice constant, that is easily integrated into nanoscale devices. Motivated by these considerations, we employ computational methods to study a substitutional Er3+ impurity (ErW) in monolayer tungsten disulfide (WS2). We start by using density functional theory (DFT) to predict its ground state atomic structure along with charge-state stabilities, while identifying potential electronic transitions via linear response theory within DFT. Strong correlations, however, prevent DFT from quantitatively describing the emerging many-body states and excitations within the 4f manifold, while the required defect supercell sizes render many-body methods inapplicable. As an attempt to overcome such limitations, we consider a quantum embedding method, recently applied to similar point-defect systems. The method is based on the constrained random phase approximation (cRPA) and a localized basis via Wannierization to construct an effective Hamiltonian that describes a subspace containing only the relevant defect states. By treating the 4f manifold of an isolated Er3+ as our correlated subspace, and benchmarking against quantum chemistry methods via the full-configuration interaction (FCI), we plan to characterize and incorporate further terms (such as spin-orbit coupling) into the effective Hamiltonian for the isolated Er3+ and extend it to the case of ErW in WS2. Such an approach could potentially describe the many-body states and 4f–4f excitations more quantitatively, with the possibility of being extended to other RE dopants in similar host matrices.

Other authors: Hampel, Alexander; d. Menon, Vinod M.; a.c. López, Gustavo E.; b.c. Dreyer, Cyrus; d.e Flick, Johannes; d. Meriles, Carlos A.
a. Department of Physics, City College of the City University of New York, New York, NY 10031, USA;
b.Department of Chemistry, Lehman College of the City University of New York, Bronx, NY 10468, USA;
c.The Graduate Center of the City University of New York, New York, NY