How can I authenticate web page using a custom native app?

I want to create a web app where users can log in using a custom native app. The reason for this is that my client wants users to be able to log in to this web app with NFC tags. The idea is to create a simple native app that reads NFC tags, asks for a PIN and, once authenticated, goes back to the web page. If I can pass some kind of auth token back to the web page, I can offer a "log in with your NFC tag" button on my web page. This button will then open a URL with a scheme specific to my login-app, thus opening the app.

My question then is: Is it possible to redirect the user back to the web app, passing the auth token, without opening yet another browser tab?