create a trigger to prevent creation of duplicate accounts

trigger duplicateAccount on Account (after insert,after update) {
    set<string> duplicateSet = new set<string>();
    Map<string,string> accMap = new Map<string,string>();
    for(Account ac:trigger.new){
        duplicateSet.add(ac.name);
         
    }
   
     for(Account a:[SELECT id,Name from Account where name IN:duplicateSet]){
         accMap.put(a.name,a.Name);
         system.debug('##############'+accMap );
    }
    for(Account account:trigger.new){
        if(accMap.containsKey(account.name)  ){    
         account.addError('Account is Already Exist');
       }
}
}