recordEditForm : event.preventDefault() not submitting the pre populated values in the form

I have a custom aura component for record creation. The onload() function calls the apex method to load values in the form. When I try to submit the form by using onsubmit(), the new record is created but its not showing the pre populated values on the new record created. I tried using event.preventDefault() and manually setting the field values in the onsubmit() handler, its not submitting the form, neither its creating a record, it throws an error saying that the record already exists with the lookup values.

In the form I'm doing the following lines of code to capture the values:

<lightning:inputField aura:id = "candidateSummaryField" feildName = "Candidate_Summary__c" /><lightning:inputField aura:id = "stageField" fieldName = "Stage__c"/>

In the controller in the onload() handler:

var stageFieldValue = component.find("stageField").set("v.value", "Contacted");var candidateSummaryFieldValue = component.find("candidateSummaryField").set("v.value", result[0]['Candidate_Summary__c']);

In the controller in the onsubmit() handler:

handleSubmit : function(component, event, helper) {        console.log("Inside handleSubmit");        event.preventDefault();        var fields = event.getParams('fields');        console.log("fields::::: "+JSON.stringify(fields));        fields['Candidate_Summary__c'] = 'New Candidate Summary';        fields['Stage__c'] = 'Contacted';        component.find("applicantForm").submit(fields);    }

Kindly suggest what I might be missing here, which is not allowing me to achieve record creation with already pre populated values from the form.

Thanks!