Use of Multigrids to Reduce the Cost of Performing Interpolative Separable Density Fitting.

In this article, we present an interpolative separable density fitting (ISDF)-based algorithm to calculate the exact exchange in periodic mean field calculations. In the past, decomposing the two-electron integrals into the tensor hypercontraction (THC) form using ISDF was the most expensive step of the entire mean field calculation. Here, we show that by using a multigrid-ISDF algorithm, both the memory and the CPU cost of this step can be reduced.

Tetracene Diacid Aggregates for Directing Energy Flow toward Triplet Pairs.

A comprehensive investigation of the solution-phase photophysics of tetracene bis-carboxylic acid [ ()] and its related methyl ester [ ()], a non-hydrogen-bonding counterpart, reveals the role of the carboxylic acid moiety in driving molecular aggregation and concomitant excited-state behavior. Low-concentration solutions of exhibit similar properties to the popular 5,12-bis((triisopropylsilyl)ethynl)tetracene, but as the concentration increases, evidence for aggregates that form excimers and a new mixed-state species with charge-transfer (CT) and correlated triplet pair (TT) character is revealed by transient absorption and fluorescence experiments. Aggregates of evolve further with concentration toward an additional phase that is dominated by the mixed CT/TT state which is the only state present in aggregates and can be modulated with the solvent polarity.

Entangled spin-polarized excitons from singlet fission in a rigid dimer.

Singlet fission, a process that splits a singlet exciton into a biexciton, has promise in quantum information. We report time-resolved electron paramagnetic resonance measurements on a conformationally well-defined acene dimer molecule, TIPS-BP1', designed to exhibit strongly state-selective relaxation to specific magnetic spin sublevels. The resulting optically pumped spin polarization is a nearly pure initial state from the ensemble.

Triplet-pair spin signatures from macroscopically aligned heteroacenes in an oriented single crystal.

The photo-driven process of singlet fission generates coupled triplet pairs (TT) with fundamentally intriguing and potentially useful properties. The quintet TT sublevel is particularly interesting for quantum information because it is highly entangled, is addressable with microwave pulses, and could be detected using optical techniques. Previous theoretical work on a model Hamiltonian and nonadiabatic transition theory, called the model, has determined that this sublevel can be selectively populated if certain conditions are met.

Clock transitions guard against spin decoherence in singlet fission.

Short coherence times present a primary obstacle in quantum computing and sensing applications. In atomic systems, clock transitions (CTs), formed from avoided crossings in an applied Zeeman field, can substantially increase coherence times. We show how CTs can dampen intrinsic and extrinsic sources of quantum noise in molecules.

Singlet fission for quantum information and quantum computing: the parallel JDE model.

Singlet fission is a photoconversion process that generates a doubly excited, maximally spin entangled pair state. This state has applications to quantum information and computing that are only beginning to be realized. In this article, we construct and analyze a spin-exciton hamiltonian to describe the dynamics of the two-triplet state.

Passivating 1T'-MoTe multilayers at elevated temperatures by encapsulation.

Several-layer 1T'-MoTe decomposes very little during heating up to ∼550 °C under flowing argon when encapsulated by multilayer hBN, as monitored by Raman scattering and optical microscopy, but largely decomposes at much lower temperatures in incompletely covered and uncovered regions. In covered regions there are small amounts of tellurium product above ∼250 °C.

Screened Charge Carrier Transport in Methylammonium Lead Iodide Perovskite Thin Films.

While organometal halide perovskites are promising for a variety of optoelectronic applications, the morphological and compositional defects introduced by solution processing techniques have hindered efforts at understanding their fundamental properties. To provide a detailed picture of the intrinsic carrier transport properties of methylammonium lead iodide without contributions from defects such as grain boundaries, we utilized pump-probe microscopy to measure diffusion in individual crystalline domains of a thin film. Direct imaging of carrier transport in 25 individual domains yields diffusivities between 0.