[SalesForce] Lightning:datatable deselect rows

I have a lightning datatable that i would like to deselect existing selected rows when i cancelled.

When i clicked cancel button, the selectedRows of lightning data table set [].
using cmp.find("ltngCmp").set("v.selectedRows", []);

then again loaded lightning:dataTable the preSelected rows are rendering issue.

POCLtngDataTable.app

<aura:application extends="force:slds">

    <aura:attribute name="renderLtngDataTable" type="Boolean" default="false"/>
    <aura:attribute name="selectedRecords" type="List" default="[]" />
    <aura:attribute name="mydata" type="Object"/>
    <aura:attribute name="mycolumns" type="List"/>
    <aura:handler name="init" value="{! this }" action="{! c.init }"/>


    <aura:if isTrue="{!v.renderLtngDataTable}">
        <lightning:card title="Demo">
            <aura:set attribute="actions">
                <lightning:button label="cancel" variant="brand" onclick="{!c.cancel}"/>
            </aura:set>
            <lightning:datatable aura:id="ltngCmp" data="{! v.mydata }" 
                                 columns="{! v.mycolumns }" 
                                 keyField="Id"

                                 onrowselection="{! c.getSelectedName }"/>
        </lightning:card>

        <aura:set attribute="else">

            <lightning:button label="RenderLtng" variant="netural" onclick="{!c.showLtng}"/>  

        </aura:set>

    </aura:if>


</aura:application>

POCLtngDataTableController.Js

({
    init: function (cmp, event, helper) {
        cmp.set('v.mycolumns', [
            {label: 'Name', fieldName: 'LastName', type: 'text'},
            {label: 'Email', fieldName: 'Email', type: 'email'}
        ]);

        var dataRecords = [];
        for(var i = 0; i < 5; i++){
            var dataRecordObj = {};
            dataRecordObj.Id = 'a' + i;
            dataRecordObj.LastName = 'kk' + i;
            dataRecordObj.Email = 'test'+ i +'@test.com';
            dataRecords.push(dataRecordObj);
        }
        cmp.set('v.mydata', dataRecords);
    },
    getSelectedName: function (cmp, event) {
        var selectedRecords = [];
        var selectedRows = event.getParam('selectedRows');
        // Display that fieldName of the selected rows
        selectedRows.forEach(function(selectedRow){
            selectedRecords.push(selectedRow);
        })
        cmp.set("v.selectedRecords", selectedRecords);
    },
    showLtng : function(cmp, event, helper){
        cmp.set("v.renderLtngDataTable", true);
    }, 
    cancel : function(cmp, event, helper){
        var ltngCmp = cmp.find("ltngCmp");
        if(ltngCmp){
            var selectedRows = ltngCmp.get("v.selectedRows");
            selectedRows.length = 0;
            ltngCmp.set("v.selectedRows", selectedRows);
        }
        cmp.set("v.renderLtngDataTable", false);
    }
})