arXiv subjects

Eugène Bertin

Publications and source records attributed to Eugène Bertin.

3 recordsLinked to original sources

arXiv2026

A modified Moss rule highlights underexplored classes of high refractive index materials

High refractive index dielectrics are central to photonic applications, yet the empirical Moss rule imposes a fundamental trade-off between refractive index and optical transparency. We introduce a modified Moss rule anchored to the optical absorption edge rather than the fundamental bandgap, capturing materials where various physical mechanisms suppress absorption well above the electronic gap. Screening the Materials Project database with this metric reveals recurring chemical compositions and structural prototypes in the materials with the most promising refractive index/transparency trade-offs. These materials include chalcopyrites, Zintl pnictides, and early transition metal multi-anion chalconitrides and oxychalcogenides compounds. Hybrid density functional theory calculations reveal that the chalconitride (Hf,Zr)2(S,Se)N2 family can achieve a combination of ultra-high refractive indices, low effective masses and transparency windows extending deep into the UV, surpassing state-of-the-art TiO2 and SiC. Our results establish (Hf,Zr)2(S,Se)N2 compounds as a unique and largely unexplored material family for next-generation photonic applications.

cond-mat.mtrl-sci↗

arXiv2026

A sulfonitride transparent conductive thin film with ultra-high refractive index

With the rise of AI-assisted materials screening, extraordinary properties are now frequently predicted in experimentally uncharted material systems, highlighting the need to develop new synthesis methods for unconventional materials beyond the classic bulk powder form. Here, we establish the first thin-film growth route for any metal sulfonitride compound by realizing Zr2SN2 films with a rare and compelling combination of optical and electrical properties. Zr2SN2 is transparent across most of the visible range while exhibiting a very high average refractive index of 2.95 in the visible, exceeding expectations based on conventional refractive index-bandgap scaling. Importantly, the same Zr2SN2 film shows degenerate n-type conductivity with carrier density above 10^20 cm-3 and intragrain mobility above 8 cm2V-1s-1, approaching those of established transparent conductive oxides. Zr2SN2 thus demonstrates that strong light-matter interaction, optical transparency and electrical conductivity can be reconciled within a single material platform, revealing a new class of high-refractive-index transparent conductors.

cond-mat.mtrl-sci↗

arXiv2026

AI-enhanced discovery and accelerated synthesis of metal phosphosulfides

Metal phosphosulfides have emerged as unique multifunctional materials, but they present unique synthesis challenges compared to more established material classes such as oxides and nitrides. As a consequence, experimental development and theoretical understanding of phosphosulfides have focused on individual compounds rather than on accelerated broad-range exploration. In this work, we first evaluate the synthesizability and band gaps of 909 hypothetical ternary phosphosulfides by density functional theory. We find 19 previously unknown thermodynamically stable compounds, including the first Si- and Ge-based phosphosulfides. For rapid band gap prediction, we then develop a multi-fidelity machine learning model to translate semilocal density functional theory band gaps into experimentally calibrated band gaps. Importantly, we extend the accelerated material development workflow to the experimental domain by demonstrating a route to high-throughput synthesis and characterization of virtually any phosphosulfide material system. The method is based on thin-film combinatorial libraries and yields over 100 unique compositions in each experiment, enabling us to synthesize four distinct phosphosulfide compounds in only four combinatorial experiments without prior synthesis recipes and without compromising on material quality. Thus, we argue that accelerated materials development workflows combining theory, artificial intelligence, synthesis, and characterization can be viable even for experimentally challenging inorganic materials.

cond-mat.mtrl-sci↗