Complex condition drupal query
As The Docs for condition says:

Parameters
$field: The name of the field to check. If you would like to add a more complex condition involving operators or functions, use where().

So let's see QueryConditionInterface::where:

Parameters
$snippet: A portion of a WHERE clause as a prepared statement. It must use named placeholders, not ? placeholders.
$args: An associative array of arguments.

Should do the trick for you.