you can do that a few different ways. If it your custom model you can do it in python:

_order = 'create_date desc'

But that will make them ordered like that in every view. 

You can do it in the view definition, but I'm not sure if you have to have that field in the view like using it in a domain, then you can just add the field and make it invisible.

<tree default_order="create_date desc">