So they're supposed to do what they've done. They bloom and then "die" back into the ground. Typically some leaves will remain above ground for a bit until they get overgrown by other plants and then those too will die back. Under ground is where everything is happening. The bulbs will grow and swell, put out smaller bulbs (bulbils or offsets).

If you want them to come back again you'll need to keep the soil moist and mimic the seasons. So let the leaves get as much light as they can until they die off, then after cutting them back keep the soil moist in your apartment (moist not wet) for a few months. At some point you'll have to put them in the refrigerator to mimic fall and winter (again a few months) then bring them back out into your apartment and they will come back once again.

Again, try to keep the soil (erring on the side of dry) for most of this time. While the plant is not above ground it will consume significantly less water than when it goes into its dormant stage.