arXiv subjects

Yu-Cheng Chiu

Publications and source records attributed to Yu-Cheng Chiu.

5 recordsLinked to original sources

arXiv2026

Organic Semiconductor Alignment via Confinement in Vapor-Guided Droplets

Organic semiconductors are lightweight, solution-processable materials with strong potential for printed and flexible electronics, from deformable displays to wearable sensors. Despite significant advances in materials synthesis and manufacturing, controlling molecular and mesoscale alignment during deposition remains a central challenge, as film morphology critically governs charge transport and device performance. Here, we demonstrate that flows developing within the intrinsically confined volume of microliter vapor-guided droplets can be harnessed to produce highly aligned organic semiconductor films. As droplets move in response to an external vapor source, internal flows align organic semiconducting nanowires within the droplet prior to deposition, yielding films with pronounced directional order. Organic field-effect transistors fabricated with this approach exhibit approximately 40% enhancement in saturation current relative to spin-coated controls. Beyond improved device performance, the contactless and compact nature of our method enables the deposition and alignment of organic semiconductors on curved and flexible surfaces. More broadly, vapor-guided droplets offer a scalable framework for the confinement-induced alignment of functional soft materials, with potential for integration into existing additive manufacturing platforms for flexible electronics and beyond.

cond-mat.soft↗

arXiv2026

Geometric Routing in Geometric Inhomogeneous Random Graphs

We present the first rigorous analysis of decentralized geometric routing in Geometric Inhomogeneous Random Graphs (GIRGs), a weight-agnostic variant of the greedy routing protocol. While greedy routing in GIRGs is known to explain the algorithmic small-world phenomenon by finding ultra-short paths of length $\Theta (\log \log n)$, it assumes additional knowledge of vertex weights beyond geometry, an assumption that is often restrictive or unavailable. We investigate whether the underlying geometry alone is sufficient for efficient navigation. We prove that for power-law weight exponent $\tau \in (2,3)$ and geometric decay parameter $\alpha > \tau - 1$, geometric routing succeeds with constant probability and finds ultra-short paths of length $\Theta (\log \log n)$, matching the optimal asymptotic guarantees for greedy routing. Our analysis further reveals that, upon success, both protocols follow a similar two-phase trajectory, consisting of a rapid ascent to the heavy vertices, followed by efficient navigation to the target. These results demonstrate that, in the appropriate regime, the network's geometry alone implicitly guides the path to the target through its high-weight core.

math.PR↗

arXiv2021

Expanding K-theoretic Schur Q-functions

We derive several identities involving Ikeda and Naruse's $K$-theoretic Schur $P$- and $Q$-functions. Our main result is a formula conjectured by Lewis and the second author which expands each $K$-theoretic Schur $Q$-function in terms of $K$-theoretic Schur $P$-functions. This formula extends to some more general identities relating the skew and dual versions of both power series. We also prove a shifted version of Yeliussizov's skew Cauchy identity for symmetric Grothendieck polynomials. Finally, we discuss some conjectural formulas for the dual $K$-theoretic Schur $P$- and $Q$-functions of Nakagawa and Naruse. We show that one such formula would imply a basis property expected of the $K$-theoretic Schur $Q$-functions.

math.CO↗

arXiv2020

Filtering cohomology of ordinary and Lagrangian Grassmannians

This paper studies, for a positive integer $m$, the subalgebra of the cohomology ring of the complex Grassmannians generated by the elements of degree at most $m$. We build in two ways upon a conjecture for the Hilbert series of this subalgebra due to Reiner and Tudose. The first reinterprets it in terms of the operation of $k$-conjugation, suggesting two conjectural bases for the subalgebras that would imply their conjecture. The second introduces an analogous conjecture for the cohomology of Lagrangian Grassmannians.

math.CO↗

arXiv2020

Solid-State Lifshitz-van der Waals Repulsion through Two-Dimensional Materials

In the 1960s, Lifshitz et al. predicted that quantum fluctuations can change the van der Waals (vdW) interactions from attraction to repulsion. However, the vdW repulsion, or its long-range counterpart - the Casimir repulsion, has only been demonstrated in liquid. Here we show that the atomic thickness and birefringent nature of two-dimensional materials make them a versatile medium to tailor the Lifshitz-vdW interactions. Based on our theoretical prediction, we present direct force measurement of vdW repulsion on 2D material surfaces without liquid immersion and demonstrate their substantial influence on epitaxial properties. For example, heteroepitaxy of gold on a sheet of freestanding graphene leads to the growth of ultrathin platelets, owing to the vdW repulsion-induced ultrafast diffusion of gold clusters. The creation of repulsive force in nanoscale proximity offers technological opportunities such as single-molecule actuation and atomic assembly.

cond-mat.mtrl-sci↗