If a company can login, as an entity, and you want to apply different rules for authentication, then you need to write one. It takes several steps.
blech, this would be a long answer.
there are links at the bottom.
Now this only gives you the what's in general.
You'll need to create another guard for auth.php, routes, controllers, and the Company Model needs to implement use Illuminate\Foundation\Auth\User as Authenticatable for your company model.
hope this get you started. ping me if you need more help.