arXiv subjects

Justin Shih

Publications and source records attributed to Justin Shih.

3 recordsLinked to original sources

arXiv2025

Scale-robust Low Resistance Transport in Atomic Layer Deposited Topological Semimetal Wafers on Amorphous Substrate

As data-centric computing advances, energy-efficient interconnects are increasingly critical for AI-driven systems. Traditional metal conductors face severe limitations at nanoscale due to increased resistivity from surface scattering. In response, this study demonstrates the first wafer-scale realization of an amorphous topological semimetal, tantalum phosphide (TaP), grown directly on amorphous SiO2 substrates (without any seed layers) using low-temperature atomic layer deposition (ALD). The resulting TaP films exhibit unconventional resistivity scaling: decreasing resistivity with decreasing thickness, reaching 227 micro-ohm cm at ~2.3 nm film thickness. This behavior, observed without crystalline order or seed layers, indicates dominant surface conduction and establishes ALD-TaP as a promising candidate for back-end-of-line integration. The films also show excellent conformality, stoichiometry control, and thermal stability up to 600 degree C. A two-channel conduction model confirms surface-dominated transport in ultrathin regimes, further supported by enhanced conductivity in multi-stacked configurations. These findings highlight the potential of amorphous topological semimetals for future high-density, low-power electronic interconnects and expand the applicability of ALD for integrating novel quantum materials at scale.

cond-mat.mtrl-sci↗

arXiv2013

On the Negative $K$-theory of Singular Varieties

Let $X$ be an $n$-dimensional variety over a field $k$ of characteristic zero, regular in codimension 1 with singular locus $Z$. In this paper we study the negative $K$-theory of $X$, showing that when $Z$ is sufficiently nice, $K_{1-n}(X)$ is an extension of $KH_{1-n}(X)$ by a finite dimensional vector space, which we compute explicitly. We also show that $KH_{1-n}(X)$ almost has a geometric structure. Specifically, we give an explicit 1-motive $[L \rightarrow G]$ and a map $G(k) \rightarrow KH_{1-n}(X)$ whose kernel and cokernel are finitely generated abelian groups.

math.KT↗

arXiv2007

Extremal Real Algebraic Geometry and A-Discriminants

We present a new, far simpler family of counter-examples to Kushnirenko's Conjecture. Along the way, we illustrate a computer-assisted approach to finding sparse polynomial systems with maximally many real roots, thus shedding light on the nature of optimal upper bounds in real fewnomial theory. We use a powerful recent formula for the A-discriminant, and give new bounds on the topology of certain A-discriminant varieties. A consequence of the latter result is a new upper bound on the number of topological types of certain real algebraic sets defined by sparse polynomial equations, e.g., the number of smooth topological types attainable in certain families of real algebraic surfaces.

math.AG↗