AngularJS コントローラー間でデータを効果的に共有するにはどうすればよいですか?

<div ng-controller="FirstCtrl">
    <input type="text" ng-model="FirstName">
    <br>Input is : <strong>{{FirstName}}</strong>
</div>

<hr>

<div ng-controller="SecondCtrl">
    Input should also be here: {{FirstName}}
</div>

var myApp = angular.module('myApp', []);

myApp.factory('Data', function(){
    var FirstName = '';
    return FirstName;
});

myApp.controller('FirstCtrl', function( $scope, Data ){

});

myApp.controller('SecondCtrl', function( $scope, Data ){
    $scope.FirstName = Data.FirstName;
});

myApp.factory('Fact', function(){
  return { Field: '' };
});

myApp.controller('FirstCtrl', function( $scope, Fact ){
  $scope.Alpha = Fact;
});

myApp.controller('SecondCtrl', function( $scope, Fact ){
  $scope.Beta = Fact;
});

<div ng-controller="FirstCtrl">
    <input type="text" ng-model="Alpha.Field">
    First {{Alpha.Field}}
</div>

<div ng-controller="SecondCtrl">
    <input type="text" ng-model="Beta.Field">
    Second {{Beta.Field}}
</div>