Twig template name for field when content type is viewed in particular view mode
Field templates have no name suggestion for the view mode.

From the linked page:


  This page lists the conventions used for the base html structure, the
  page, regions, blocks, nodes, fields, and other core components. (It's
  good to know that it is possible to create custom template name
  suggestions using function hook_theme_suggestions_HOOK_alter.)


You have to create a custom name suggestion.

You find the view mode in the variables of the field: Getting node view mode in field preprocess