How to use two models in a controller

Your example works just fine. Personally, I'd use the model() helper just to ensure I don't get more than 1 instance of the model created, but what you've done works fine.

EDIT:

if you're just using a model in a single method, there's no need to assign it to $this, just use a local variable:

PHP Code:

$authenticationModel = new AuthenticationModel();
$username = $this->request->getPost('username');
$password = $this->request->getPost('password');

$boolen = $authenticationModel->authentication($username, $password); 


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