Angular JS: input[radio] doesn't work

Here is my code:

<div ng-controller="TestController">
    <input ng-repeat="item in array" ng-model="selected.name" value="{{item.name}}" type="radio"></input>
</div>
<script type="text/javascript">
    var app = angular.module('app', []);
    app.controller('TestController', function ($scope) {
        $scope.array = [{
            name: 'lee',
            seq: 1,
        }, {
            name: 'tom',
            seq: 2,
        }, {
            name: 'jack',
            seq: 3,
        }];

        $scope.selected = $scope.array[0];
    });
</script>

When the page is show, the default checked radio box is correct. But it can not be un-check,and I can only switch between the other two checkbox? How can I fix this problem?