Unique validation with condition in Laravel

I want to soft delete some records from my user table, but when any users try to register with same deleted username then i do not want to check for unique username in rows where deleted_at is filled with date for that i'm using this code but it is not working.

$validator = Validator::make($request->all(), [
        'name' => 'required','email'=>'unique:users,email,NULL,NULL,deleted_at,NULL','password'=>$hashed_random_password,
    ]);

via Chebli Mohamed