How to pan sear a thin steak?
I would actually recommend the opposite of what was said above. Since the meat is so thin you may have much better results pan searing it in an extremely hot pan from slightly frozen. This way the outermost layer will start to undergo the maillard reaction long before the inside of the steak reaches a medium-rare temp and will give you a better chance of preventing it from overcooking. 

This link provides an overview of the process for a much larger piece of meat then your using but the searing process is what your concerned most with since your steaks are so thin. You will likely have to play with the timing a little bit with regards to how frozen the steak needs to start out but I figure erring on the side of too frozen is best since you can then heat them in the oven to the internal temp your looking for. 

http://www.thekitchn.com/for-the-perfect-steak-first-freeze-it-solid-then-cook-for-an-hour-165793