Use
in the search box, without the apostrophes.
You might want to read the
calibre manual section on searching and the
calibre manual section on the tag browser.
Four hints:
1) If you click on a tag in the tag browser pane (usually on the left), that tag shows with a green + and you search for all books containing that tag. If you click the tag again, you see a red - and you search for books not containing that tag. Use this to see what the search values look like.
2) If you hold the shift or ctrl key while clicking in the tag browser, you can construct more complex multi-criteria searches.
3) You can save a search, then use it as a "restriction", creating a virtual library of the books that match the search.
4) You can set a restriction to apply at start up, which may be what you were asking for when you said "by default". See preferences -> behavior -> Restriction to apply ...