good question. Depends on the structure of the game but in most H/L games played in card rooms and casinos they have an 8-or-better qualifier. So the low hand must have all five cards of 8 or less without pairs. Flushes and straights are irrelevant. The best low hand would be A-2-3-4-5 and the lowest low hand would be 4-5-6-7-8.

If I had A-2-3-4-6, it could only be beaten by a wheel.

Depending on the rest of the cards, it is possible that the person with the AA could still get at least half the pot for the high hand. Or if there was no low hand, then the AA might get the whole pot.