After looking back over some finite field theory, I've been thinking about the ring $\mathbb{Z}/p^k\mathbb{Z}$ for some prime $p$.
I'm just curious, are the $\mathbb{Z}/p^k\mathbb{Z}$ simple modules all isomorphic to each other? I suppose a better question to ask is: does $\mathbb{Z}/p^k\mathbb{Z}$ have a simple module, and if so, is it unique up to isomorphism?
I'd even appreciate a reference if this idea is collected somewhere. Thank you.