I have been reading about sous vide cooking and it seems like sous vide cooking is done under pressure. I want to try cooking a steak sous vide in a pressure cooker and then searing it to create a nice crispy edge at the end. Is this possible with a pressure cooker? What specific temperature and time frame should I consider for beef steak? Are there any weight graphs available to determine the time required?
I'm afraid you have gotten something wrong.
Sous-vide and pressure cooking are, as far as food physics is concerned, on the opposite ends of the scale.
Pressure cooking allows you to increase the boiling point of water, thus reducing the cooking time. (Bad idea for a tender steak, btw., as soon as you exceed a certain temperature, the proteins in the meat change irreversibly and the meat gets tough.)
Sous-vide uses temperatures way below the boiling point, combined with a very extended cooking time. This means you can safely and slowly bring your steak to the desired core temperature without the risk of overcooking and thus toughening the meat. A final sear is just a finishing touch, not technically a necessity for cooking the meat. (But don't skip it, it's for flavour and eye appeal!)
So no, we can't give you a temperature / time chart for steak in a pressure cooker - because the results would be very unsatisfactory.
Different Terminology. Sous vide literally means 'under vacuum' and is a subset of low temperature cooking and it's the precise holding of the meat at a given low temperature for a prolonged time that really defines the technique and a waterbath is an effective way of storing and regulating a stable temp.
In order for it to work well you put your meat in a plastic bag and get as much air out as possible of which the most effective way is to vacuum pack the meat. The notion of 'pressure' may have derived from e.g Thomas Keller's book "Under Pressure: Cooking Sous Vide". By creating a vacuum in the bag, at the time of bagging (not cooking) the air pressure outside is pushing in on the bag and the meat and it helps shape it, keep any juices in contact with meat and minimises the distance between meat and water (any trapped air will create a resistance to heat distribution). This is not the same as the pressure in a pressure cooker.
Classically a pressure cooker is used for cooking 'tough' cuts of meat in reduced time. So stews and meats with lots of connective tissue are particularly suited. An example is a smoked ham hock. It takes me three hours to cook one by simmering in water, but only 45 mins in the pressure cooker.
If you were to try and use a pressure cooker to cook a steak, it would essentially steam the meat at over 120 degrees celcius and completely overcook it.
I believe you can. Put your meat in an aluminium foil. Then into your ziplock bag. Seal it. Bring lots of water in your pressure cooker to a boil, then lower the heat to the lowest. Then immerse the bag inside. Cook it for half the time you boil your meat. Take out your meat and sear it with some seasoning. Bon appetit!