arXiv subjects

Henry G. Bell

Publications and source records attributed to Henry G. Bell.

4 recordsLinked to original sources

arXiv2025

Three-dimensional electronic domain correlations in 1T-TaS2

The interplay of nanoscale electronic domains underpins many emergent phenomena of quantum materials, including the competition between charge density waves (CDW) and superconductivity in high-Tc cuprates, or the storage of information in phase-change memory devices. Coupling to electronic domains provides an observable for pinpointing key interactions, e.g. affecting phase transitions. While the equilibrium phase diagram of 1T-TaS2 - characterized by unique transport properties and varying degrees of CDW commensurability - has been studied extensively, an understanding of how the electronic domains in the bulk behave across phase boundaries is lacking. We reveal the three-dimensional evolution of electronic domains in 1T-TaS2 using temperature-dependent X-ray diffraction and reciprocal space mapping, complemented by structure factor simulations based on the Hendricks-Teller method. With this methodology, we identify an increasing number of stacking faults near the phase transitions, and a growing fraction of dimerized layers in the commensurate phase upon cooling. We provide structural evidence that the CDW domains mediate the transport properties at phase boundaries, and that they also account for an anomalous intermediate electronic phase within the triclinic regime upon heating. As a paradigmatic material with potential in phase-change memory applications, our study underscores the importance of domain sizes and layer stacking in defining electronic behaviors of van der Waals materials.

cond-mat.str-el↗

arXiv2025

Effect of Interlayer Stacking on the Electronic Properties of 1$T$-TaS$_2$

Controlled stacking of van der Waals materials is a powerful tool for exploring the physics of quantum condensed matter. Given the small binding between layers, exploitation for engineering will require a breakthrough in stacking methodology, or an ability to take advantage of thicker defective stacks. Here we describe computational groundwork for the latter, using -- on account of its promise for cold memory applications -- 1$T$-TaS$_2$ as a model system. Comparing recursive Hendricks-Teller calculations and Monte Carlo simulations to published X-ray diffraction data, we obtain the key parameters describing the random stacking in mesoscopic flakes. These then regulate the electronic structures via specification of the random stacks in dynamical mean-field theory simulations. Hubbard repulsion induces strongly correlated metallic, band and Mott insulating layers, providing compelling evidence that electronic properties follow from the coexistence of more than the metallic and insulating planes associated by ordinary band theory.

cond-mat.str-el↗

arXiv2025

Imaging of electrically controlled van der Waals layer stacking in 1T-TaS2

Van der Waals (vdW) materials exhibit a variety of states that can be switched with low power at low temperatures, offering a viable cryogenic "flash memory" required for the classical control electronics for solid-state quantum information processing. In 1T-TaS2, a non-volatile metallic 'hidden' state can be induced from an insulating equilibrium charge-density wave ground state using either optical or electrical pulses. Given that conventional memristors form localized, filamentary channels which support the current, a key question for design concerns the geometry of the conduction region in highly energy-efficient 1T-TaS2 devices. Here, we report in operando micro-beam X-ray diffraction, fluorescence, and concurrent transport measurements, allowing us to spatially image the non-thermal hidden state induced by electrical switching of 1T-TaS2. Our results reveal a long-range ordered, non-filamentary switched state that extends well below the electrodes, implying that the self-organized, collective growth of the hidden phase is driven by a combination of charge flow and lattice strain. Our unique combination of techniques showcases the potential of non-destructive, three-dimensional X-ray imaging to study bulk switching properties in microscopic detail, namely electrical control of the vdW layer stacking.

cond-mat.str-el↗

arXiv2021

A single-layer based numerical method for the slender body boundary value problem

Fluid flows containing dilute or dense suspensions of thin fibers are widespread in biological and industrial processes. To describe the motion of a thin immersed fiber, or to describe the forces acting on it, it is convenient to work with one-dimensional fiber centerlines and force densities rather than two-dimensional surfaces and surface tractions. Slender body theories offer ways to model and simulate the motion of immersed fibers using only one-dimensional data. However, standard formulations can break down when the fiber surface comes close to intersecting itself or other fibers. In this paper we introduce a numerical method for a recently derived three-dimensional slender body boundary value problem that can be stated entirely in terms of a one-dimensional distribution of forces on the centerline. The method is based on a new completed single-layer potential formulation of fluid velocity which removes the nullspace associated with the unmodified single layer potential. We discretize the model and present numerical results demonstrating the good conditioning and improved performance of the method in the presence of near-intersections. To avoid the modeling and numerical choices involved with free ends, we consider closed fibers.

math.NA↗