AlpineJS model not updating via jQuery ajax callback

I am trying to update a checkbox value tied to a AlipneJS data model based on the response of a jquery ajax call.
However it doesn’t seem to work when I try to update the data model for the checkbox in the jQuery callback method. It updates fine before the jquery call (the commented out line works fine).

What am I missing? Thanks for your help in advance.

<html>
<head>
    <!--- jQuery --->
    <script src="https://code.jquery.com/jquery-3.7.1.min.js" integrity="sha256-/JqT3SQfawRcv/BIHPThkBvs0OEvtFFmqPF/lYI/Cxo=" crossorigin="anonymous"></script>
    <!--- Bootstrap --->
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" integrity="sha384-T3c6CoIi6uLrA9TneNEoa7RxnatzjcDSCmG1MXxSR1GAsXEV/Dwwykc2MPK8M2HN" crossorigin="anonymous">
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.min.js" integrity="sha384-BBtl+eGJRgqQAUMxJ7pMwbEyER4l1g+O15P+16Ep7Q9Q+zqX6gSbd85u4mG4QzX+" crossorigin="anonymous"></script>

    <!--- Include Alpinejs --->
    <script defer src="https://cdn.jsdelivr.net/npm/[email protected]/dist/cdn.min.js"></script>
</head>

<body>
    <div style="width:50%;margin:auto;line-height:2em;">
        <div x-data="startup">
            <form>
                <div>Checkbox<sup class="text-danger">*</sup></div>
                <div class="form-check">
                    <input class="form-check-input big-checkbox material" type="checkbox" value="" id="yes" x-model="val_yes">
                    <label class="form-check-label" for="flexCheckDefault">
                    Yes
                    </label>
                    <br>
                    <button class="btn btn-primary mt-3" @click.prevent="callAPI()">Call API</button>
                </div>
            </form>
        </div>
    </div>

    <script>
         document.addEventListener('alpine:init', () => {
            Alpine.data('startup', () => ({
                val_yes: false,
                callAPI()
                    {
                        //this.val_yes = true;
                        $.ajax({
                                url:"https://zenquotes.io/api/today",
                                dataType: 'json',
                                success: function(json) 
                                    {
                                        this.val_yes = true;
                                    }
                            });
                    
                    }
            }))
        })
    </script>

</body>
</html>