Hi Samarjit
I agree with Mike , the more I think of your problem I wonder where the vapour barrier actually is . It is normal practice to have the barrier create an envelope right round the sub zero room. With the continuous Ali floor how is the vapour barrier maintained up on to the warm side of the insulated panel dividing wall with the anti room. I agree with your idea of creating a thermal isolation by cutting the continuous Ali floor but if the vapour barrier is not maintained there is the danger of "Frost Heave" which could lead to much bigger problems with the general structure.
Regards
JH