arXiv subjects

Robert Dawson

Publications and source records attributed to Robert Dawson.

5 recordsLinked to original sources

arXiv2026

Phonon assisted absorption in Transition Metal Dichalcogenide heterostructures

The coupling of atomic vibrations to electronic excitations - traditionally understood to be a source of energy loss in semiconductors - has recently been explored in photosynthetic light harvesting as a means to circumvent dissipation by harnessing quantum vibronic coherence. Motivated by recent photocurrent measurements of vibronic sidebands in WSe$_2$/MoSe$_2$ optoelectronic devices, we present a nonperturbative theoretical framework for phonon-assisted absorption in van der Waals heterostructures. Using a polaron transformation, a closed-form expression for the optical absorption spectrum at arbitrary temperatures is presented. Our model includes both intraband and interband electron-phonon coupling. Detailed analysis shows that the observed periodic sidebands originate from the strong coupling between interlayer excitons and nearly dispersionless optical phonon modes. Comparing two limiting cases - one involving only intraband couplings, and another incorporating coherent interband processes - we show that interband phonon-assisted transitions are needed to account for the observed data. Beyond enabling the direct estimation of vibronic coupling strengths from spectroscopic data, these findings have profound consequences for our understanding of optical and optoelectronic responses: coherent interband coupling of atomic vibrations to excitons is essential to quantifying photoresponse in transition metal dichalcogenide heterostructures.

cond-mat.mtrl-sci↗

arXiv2024

Proximity effect of s-wave superconductor on inversion broken Weyl Semi-Metal

Inducing superconductivity in systems with unconventional band structures is a promising approach for realising unconventional superconductivity. Of particular interest are single interface or Josephson Junction architectures involving Weyl semimetals, which are predicted to host odd parity, potentially topological, superconducting states. These expectations rely crucially on the tunneling of electronic states at the interface between the two systems. In this study, we revisit the question of induced superconductivity in an inversion broken WSM via quantum tunneling, treating the interface as an effective potential barrier. We determine the conditions under which the gap function couples to the Weyl physics and its properties within the WSM. Our simulations show that the mismatch in the nature of the low energy electronic states leads to a rapid decay of the superconductivity within the semi-metal.

cond-mat.supr-con↗

arXiv2021

Taut and Tense Networks

Geometrical constructions using flexible cords have been known since the earliest days of recorded mathematics. In this paper we introduce rigorous definitions for two classes of string networks. A taut network is one in which all cords are tight in every possible configuration; a tense network has configurations in which one or more cords are not tight, but is externally constrained to avoid such configurations. We show that taut networks compute only affine linear functions and subspaces, whereas tense networks (which are closely related to linkages) can trace any algebraic curve.

math.MG↗

arXiv2021

Telescopic, Multiplicative, and Rational Extensions of Summations

A summation is a shift-invariant ${\rm R}$-module homomorphism from a submodule of ${\rm R}[[σ]]$ to ${\rm R}$ or another ring. [11] formalized a method for extending a summation to a larger domain by telescoping. In this paper, we revisit telescoping, we study multiplicative closures of summations (such as the usual summation on convergent series) that are not themselves multiplicatively closed, and we study rational extensions as a generalization of telescoping.

math.AC↗

arXiv2021

Fast-growing series are transcendental

Let $R$ be a subring of $\mathbb{C}[[z]]$, and let $X \in \mathbb{C}[[z]]$. The Newton-Puiseux Theorem implies that if the coefficients of $X$ grow sufficiently rapidly relative to the coefficients of the series in $R$, then $X$ is transcendental over $R$. We prove an alternative proof of this result by establishing a relationship between the coefficients of $A(X)$ and $A^\prime(X)$, where $A(T)$ is a polynomial over $\mathbb{C}[[z]]$.

math.NT↗