arXiv subjects

Annabelle Canestraight

Publications and source records attributed to Annabelle Canestraight.

8 recordsLinked to original sources

arXiv2026

Floquet-Plasmon Enhanced Charge Transfer at Catalytic Interfaces

Plasmonic excitation of metallic nanostructures can generate energetic carriers capable of transferring charge into nearby adsorbed molecules, providing a possible pathway for driving chemical transformations. In many theoretical descriptions of this process, charge transfer is determined by the equilibrium electronic structure of the molecule and substrate together with the time-dependent carrier distribution produced during plasmon decay. However, the intense transient electric fields associated with localized surface plasmons can also dynamically perturb the molecular electronic structure itself on ultrafast timescales. In this work, we investigate how these time-dependent fields modify the molecular spectral function and influence charge injection at catalytic interfaces. Using a model of CO2 adsorbed on Au(111), we compute the real-time molecular Green's function within a correlated frontier-orbital active space under plasmon-like driving. We find that the driving field rapidly produces transient Floquet-type replica bands in the molecular density of states, opening additional resonant pathways for hot-carrier injection that are absent without external driving or in time-local descriptions. Coupling the evolving molecular spectrum to a time-dependent hot-electron distribution described within a two-temperature Sommerfeld framework, we predict large enhancements in quasiparticle spectral overlap that governs injection during plasmon dephasing. These results suggest that dynamically generated non-equilibrium spectral structure may play an important role in plasmon-assisted catalysis and provide a framework for studying driven catalytic interfaces beyond static electronic structure descriptions.

physics.chem-ph↗

arXiv2026

Stochastic Cluster Expansion for Excited State Energies

Excited-state electronic structure in strongly correlated systems remains challenging due to the exponential scaling of the many-body Hilbert space and the difficulty of constructing systematically controlled active spaces. Building on the stochastic cluster expansion (SCE) framework previously developed for ground-state correlation energies, we extend the formalism to excitation gaps by expressing energy differences directly as a hierarchy of orbital-space cluster contributions. In this formulation, excitation energies are reconstructed from reduced-rank calculations involving a minimal frontier chemical subspace (FCS), treated exactly, together with stochastic sampling of the remaining orbital environment. This approach eliminates the need for large or chemically preselected active spaces. We demonstrate the method on charge-transfer complexes and polyacenes, where accurate singlet-triplet gaps are obtained that agree with full-system results. The method converges with low-order cluster terms and provides a systematically improvable framework for excited states in correlated systems.

physics.chem-ph↗

arXiv2026

A Stochastic Cluster Expansion for Electronic Correlation in Large Systems

Accurate many-body treatments of condensed-phase systems are challenging because correlated solvers such as full configuration interaction (FCI) and the density matrix renormalization group (DMRG) scale exponentially with system size. Downfolding and embedding approaches mitigate this cost but typically require prior selection of a correlated subspace, which can be difficult to determine in heterogeneous or extended systems. Here, we introduce a stochastic cluster expansion framework for efficiently recovering the total correlation energy of large systems with near-DMRG accuracy, without the need to select an active space a priori. By combining correlation contributions from randomly sampled environment orbitals with an exactly treated subspace of interest, the method reproduces total energies for non-reacting and reactive systems while drastically reducing computational cost. The approach also provides a quantitative diagnostic for molecule-solvent correlation, guiding principled embedding decisions. This framework enables systematically improvable many-body calculations in extended systems, opening the door to high-accuracy studies of chemical processes in condensed phase environments.

cond-mat.mtrl-sci↗

arXiv2026

Influence of Markovianity and self-consistency on time-resolved spectral functions of driven quantum systems

We present a systematic comparison of the real-time Dyson expansion (RTDE) with established non-equilibrium Green's function approaches for simulating driven, interacting quantum systems. Focusing on density matrix dynamics, time-off-diagonal Green's functions, and time-resolved photoemission spectra, we benchmark RTDE against fully self-consistent Kadanoff-Baym equation (KBE) calculations, the generalized Kadanoff-Baym ansatz (GKBA), and exact diagonalization for small systems using second order many-body perturbation theory. Using a driven two-band Hubbard model, we show that mean-field single particle density matrix trajectories provide a reliable baseline for RTDE across a broad range of interaction strengths and excited-carrier populations. Further, RTDE accurately captures correlation effects in the Green's functions, including long-lived oscillations and revivals that are strongly suppressed by the overdamping inherent to self-consistent KBE schemes. As a consequence, RTDE resolves rich non-equilibrium spectral structure in time-resolved photoemission, such as interaction- and population-dependent quasiparticle splittings and bandgap renormalization, which are largely washed out in self-consistent approaches, yet are present in the exact solutions. Our results demonstrate that RTDE bridges the gap between mean-field propagation and full two-time KBE simulations, retaining favorable linear scaling while capturing essential dynamical correlations relevant for ultrafast spectroscopy.

cond-mat.str-el↗

arXiv2024

Renormalization of States and Quasiparticles in Many-body Downfolding

We explore the principles of many-body Hamiltonian complexity reduction via downfolding on an effective low-dimensional representation. We present a unique measure of fidelity between the effective (reduced-rank) description and the full many-body treatment for arbitrary (i.e., ground and excited) states. When the entire problem is mapped on a system of interacting quasiparticles [npj Computational Materials 9 (1), 126, 2023], the effective Hamiltonians can faithfully reproduce the physics only when a clear energy scale separation exists between the subsystems and its environment. We also demonstrate that it is necessary to include quasiparticle renormalization at distinct energy scales, capturing the distinct interaction between subsystems and their surrounding environments. Numerical results from simple, exactly solvable models highlight the limitations and strengths of this approach, particularly for ground and low-lying excited states. This work lays the groundwork for applying dynamical downfolding techniques to problems concerned with (quantum) interfaces.

physics.comp-ph↗

arXiv2024

Delocalization of Quasiparticle Moiré States in Twisted Bilayer hBN

Twisted bilayers host many emergent phenomena in which the electronic excitations (quasiparticles - QPs) are closely intertwined with the local stacking order. By inspecting twisted hexagonal boron nitride (t-hBN), we show that non-local long-range interactions in large twisted systems cannot be reliably described by the local (high-symmetry) stacking and that the band gap variation (typically associated with the moiré excitonic potential) shows multiple minima with variable depth depending on the twist angle. We investigate twist angles of 2.45$^\circ$, 2.88$^\circ$, 3.48$^\circ$ and 5.09$^\circ$ using the GW approximation together with stochastic compression to analyze the QP state interactions. We find that band-edge QP hybridization is suppressed for intermediate angles which exhibit two distinct local minima in the moiré potential (at AA region and saddle point (SP)) which become degenerate for the largest system (2.45$^\circ$).

cond-mat.mtrl-sci↗

arXiv2023

Efficient Quasiparticle Determination beyond the Diagonal Approximation via Random Compression

Calculations of excited states in Green's function formalism often invoke the diagonal approximation, in which the quasiparticle states are taken from a mean-field calculation. Here, we extend the stochastic approaches applied in the many-body perturbation theory and overcome this limitation for large systems in which we are interested in a small subset of states. We separate the problem into a core subspace, whose coupling to the remainder of the system environment is stochastically sampled. This method is exemplified on computing hole injection energies into CO$_2$ on an extended gold surface with nearly 3000 electrons. We find that in the extended system, the size of the problem can be compressed up to $95\%$ using stochastic sampling. This result provides a way forward for self-consistent stochastic methods and determining Dyson orbitals in large systems.

physics.comp-ph↗

arXiv2023

Exceptional spatial variation of charge injection energies on plasmonic surfaces

Charge injection into a molecule on a metallic interface is a key step in many photo-activated reactions. The energy barrier for injection is paralleled with the lowest particle and hole addition energies. We employ Green's function formalism of the many-body perturbation theory and compute the excitation energies, which include non-local correlations due to charge density fluctuations on the surface, i.e., the plasmons. We explore a prototypical system: CO$_2$ molecule on nanoscale plasmonic Au infinite and nanoparticle surface with nearly 3,000 electrons. In contrast to widely used density functional theory, we demonstrate that the energy barrier varies significantly depending on the molecular position on the surface, creating "hot spots" for possible carrier injection. These areas arise due to an intertwined competition between purely plasmonic couplings (charge density fluctuations on the substrate surface alone) and the degree of hybridization between the molecule and the substrate. There are multiple positions found with the lowest energy barrier for the electron/hole injection. We identify that the charge injection barrier to the adsorbate on the plasmonic surface trends down from the facet edge to the facet center -- here, the change in molecular orbitals overshadows the role of the charge fluctuations in the substrate. This finding contrasts the typical picture in which the electric field enhancement on the nanoparticle edges is considered the most critical factor.

physics.chem-ph↗