how to put symbol on top of tensor product

Question

How do I put a $\frown$ right on top of $\otimes$? I tried \stackrel but it leaves too much space between symbols.

Answer 1

Here's a possibility:

\documentclass{article}
\usepackage{amsmath}

\makeatletter
\DeclareRobustCommand\frownotimes{\mathbin{\mathpalette\frown@otimes\relax}}
\newcommand{\frown@otimes}[2]{%
  \vbox{
    \ialign{##\cr
      \hidewidth$\m@th#1{}_\frown$\kern-\scriptspace\hidewidth\cr
      \noalign{\nointerlineskip\kern-1pt}
      $\m@th#1\otimes$\cr
    }%
  }%
}
\makeatother

\begin{document}

$A\frownotimes B_{x\frownotimes y}$

\end{document}

Answer 2

\documentclass{article}
\usepackage{stackengine,scalerel}
\def\frownotimes{\mathbin{\ThisStyle{\ensurestackMath{\stackengine{-1.4\LMpt}{%
  \SavedStyle\otimes}{\mkern1mu\SavedStyle_\frown}{O}{c}{F}{T}{S}}}}}
\begin{document}
$A \frownotimes B_{x \frownotimes y}$
\end{document}