How to sum value by month and assign two different variables?

I wish to sum up payment_amount by created_at date and assign the total by month to two different variables so I can plot on charts js x and y axis.

So far i have output json string using the below code.

 public function index()
{

    $data = [
    'period' => Payment::all('created_at', 'payment_amount')->groupBy(function($date) {
    return Carbon::parse($date->created_at)->format('F');
    })->tojson(),
    ];

    //dd($data);
    return view('admin.dashboard', $data);  
    }   

so to one json string I wish to have $created_at //which goes on the x axis $total payment_amount //which goes on y axis.

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