I'm writing the introduction to my Ph.D. thesis in theoretical physics. It is fairly interdisciplinary sandwich thesis. I have already written a Background section were I write some of the necessary background knowledge necessary to the motivations and the context of the paper. So I am left with writing a shortish introduction section. Can this section be written in 1st person, explaining why I find this work interesting and why I was led to work in this specific area?
Can this section be written in 1st person, explaining why I find this work interesting and why I was led to work in this specific area?
No, you should instead explain why your reader (an imaginary physicist with knowledge of your field but without expertise in your specific topic) should find this work interesting, and how the current state of research led you to work on your research question.
Leave the subjective and biographical remarks about your personal motivation for the preface (if any) and acknowledgement section.
For any reader interested in your results, that would just be noise that gets in the way. Something they need to scan over to reach what you really need to say.
I'd recommend against this and suggest you keep to the topic. A shortish introduction might be a good thing, actually.
Those kinds of personal stories are something that might go in a blog or on a personal website. Keep the thesis (and other professional writing) strictly professional - at least until you have built a solid standing in your career.