Applied Physics Letters Formatting Requirements: Complete Author Guide

APL's abstract follows a straightforward format with no structural subdivisions.

• Word limit: 250 words maximum
• Structure: Unstructured (single paragraph)
• Citations: Not permitted in the abstract
• Footnotes: Not permitted in the abstract
• Keywords: APL doesn't require author-supplied keywords in the abstract block. Subject classifications are handled through the submission system using AIP's Physics and Astronomy Classification Scheme (PACS) codes or their replacement terms.

The abstract should summarize the purpose, methods, and principal findings of the work. Since APL papers are short, the abstract often reads as a compressed version of the entire paper. Don't waste space restating well-known facts. Get to your specific contribution within the first two sentences.

AIP journals, including APL, treat the abstract as a standalone document for indexing purposes. That means abbreviations defined in the abstract must be redefined at first use in the body text. This is a small formatting detail that production staff will flag if you miss it.

Space is the defining constraint in APL. With a 4-page target, figures compete directly with text for real estate.

Figure specifications:

Practical figure advice for APL:

Most successful APL papers use 3 to 4 figures. You won't find a formal cap, but the page constraint makes more than 4 figures difficult to fit. Multi-panel figures are common and often necessary. A single figure with panels (a) through (d) is typical.

Color figures are published at no extra charge in the online version. APL moved to free color online years ago, and since the journal is primarily read digitally, there's no practical reason to avoid color. However, make sure your figures are legible in grayscale if you expect readers to print them.

Tables are relatively uncommon in APL because the letters format doesn't give you room for large datasets. When tables are used, they should be created using the standard LaTeX tabular environment or Word table tools, not inserted as images.

APL uses the standard AIP citation style, which is a numbered sequential system.

In-text citations: Superscript numbers (e.g., "as demonstrated previously^1,2"). Numbers are assigned in the order references first appear in the text. For multiple consecutive references, use a range: ^1-3 rather than ^1,2,3.

Reference list format:

1. A. B. Author, C. D. Author, and E. F. Author, "Title of article," J. Abbrev. Name Volume, Pages (Year).

Key formatting details for AIP style:

• Author names: Initials first, then surname (e.g., "J. K. Smith").
• Use "and" before the last author (not "&").
• Journal titles abbreviated per the Chemical Abstracts Service Source Index (CASSI).
• Article titles are included and placed in quotation marks.
• Volume numbers are in bold.
• Issue numbers are generally omitted.
• Page ranges use an en dash in final typesetting.
• DOIs are strongly encouraged and will be added by production if missing.

There's no hard cap on references, but APL papers typically cite 20 to 30 sources. Reviewers will notice if your reference list is padded with tangentially related papers. In a letters journal, every citation should directly support a specific claim.

APL uses the REVTeX 4.2 bibliography style file (aipnum4-2.bst) for BibTeX users. This handles the formatting automatically. If you're using Word, you'll need to format references manually or use a citation manager set to AIP style.

APL supports supplementary material for data, figures, and multimedia that don't fit within the 4-page letter format.

What can go in supplementary material:

• Additional figures and tables
• Detailed derivations and mathematical proofs
• Extended datasets
• Multimedia files (videos, animations)
• Code and computational details

Supplementary material is hosted by AIP Publishing and linked from the published article. It goes through peer review alongside the main manuscript. The supplementary file should be submitted as a single PDF for text and figures, with multimedia files submitted separately.

AIP requires a "supplementary material" section at the end of the main text (before references) that briefly describes what the supplementary file contains. This is typically one or two sentences. Don't assume reviewers will read the supplementary in detail. The main text should be self-contained, with supplementary material providing supporting evidence.

There's a 10 MB size limit per supplementary file. For larger datasets, AIP recommends depositing in a public repository and citing the DOI in the paper.

These are the details that regular APL authors know but first-timers miss:

No Introduction heading. APL papers don't use an "Introduction" section heading. The paper begins directly with introductory text. The first formal heading is usually something like "Experimental Methods" or "Theoretical Framework." This is consistent across AIP letters journals.

Author affiliations use superscript numbers. AIP style links authors to affiliations using superscript numbers, not symbols or footnotes. The corresponding author is identified with a superscript "a)" and the email address is listed in a footnote. Example: "J. Smith^1,a)" with footnote "a)Electronic mail: jsmith@university.edu".

PACS codes are being phased out. APL historically used PACS codes for subject classification. These are being replaced by AIP's subject taxonomy, which you'll select during the online submission process. Don't include PACS codes in the manuscript itself.

Equation formatting. Equations are numbered sequentially in parentheses, right-justified: Eq. (1), Eq. (2), etc. In-text references use "Eq." (capitalized) at the start of a sentence and "Eq." elsewhere. Don't spell out "Equation" in the text.

Acknowledgments section. Placed before the references. Funding sources, facility access, and computational resources should be acknowledged here. AIP requires that funding agency names match their official registered names.

Data availability statement. AIP now requires a data availability statement for all articles. This appears after the acknowledgments and before the references. Even if all data is contained within the article, you still need the statement.

These trip up authors more than they should:

1. Figure captions count toward the word limit. Unlike many journals where captions are excluded, APL includes captions in the word count. Keep them concise.

1. Single PDF for initial submission. Don't submit text and figures as separate files on the first round. Everything goes in one PDF. Separate files are for the revision stage.

1. No "Dear Editor" cover letter field. AIP's submission system doesn't have a traditional cover letter upload for APL. Instead, there's a comments field where you can provide a brief description of the work's significance.

1. Supplementary material must be cited. Every supplementary file must be referenced in the main text. Orphaned supplementary material will be flagged.

1. Units follow SI conventions. AIP requires SI units throughout. If non-SI units are necessary for the field (e.g., eV for energy in semiconductor physics), they can be used alongside SI equivalents.