How to find corresponding record of child table from parent record

I am doing a project in laravel and using backpack for making admin panel. I have a table named users and another table user_details in which primary key of users table is used as a foreign key. My question is that how can i access details of a particular user from parent table id. In laravel auth and backpack, I can do stuff like

auth()->user()->id;

or for backpack I can use

backpack()->user()->id;

Similarly I thought i would be able to get all columns of user_details page by doing this:

backpack()->user()->user_details;

But it's not working this way ?? Any help will be greatly appreciated!

via Chebli Mohamed