I am currently doing a PhD in theoretical physics (let's for simplicity say gravity and black holes). However, I have also in my free time been working a bit in a more applied field (let's say cold atom physics), and have been reasonably successful (in the sense that I have some publications, and a couple of ideas of projects that I could do if I had more time, and I have good connections with collaborators in this field). I am now facing (or I will be facing) and important decision: After my PhD, if I want to continue in academia, should I continue and focus all my attention on theoretical physics, or should I try to get serious with my other research line and do 50-50? I can see advantages and disadvantages with both: In theoretical physics, the funding is very limited, and thus it is very hard to land jobs (especially faculty positions). Thus also doing research in a more applied field might give more job opportunities since there should be more money. However, I understand that I risk crippling myself in both fields, so that I will not be able to apply for job openings that are for instance purely directed at theoretical physics (for instance job openings with professors that have a personal grant for a specific subject). But for faculty positions, maybe it would be an advantage to have a more broad research interest? What are your opinions on this?