I just started a 3-4 year Post-Doc position in Department A, to work on a topic on the border between two fields on which they also work in Department B.

In some European countries the usual situation is to do a Habilitation in A. However, theoretically it is also possible to get payed by department A, and working on projects for A, but doing a second PhD department B as an external PhD candidate (as if i where in an external research institute), in stead of doing a Habilitation in A. Doing a "external" PhD, at an other place than the supervising Professor is quite common in Germany, Italy and a few other EU countries. But only if the other place is a research institute or company, doing that in another university group, or university is very uncommon/rare, especially when it is about doing a second PhD. I am not easily persuaded by uncommon/rare by itself, so i would like to know the pros and cons of taking this unusual path?

Honestly only see more advantages (more collaborators, shared expertise) especially for topics that are on the border between two fields. A Habilitation can easily be waved if you have enough publications. It seems to me that a second PhD in B will later make it easier to change fields to B, beyond only the topics on the border between A and B. On the other hand i do not know any people who did something like this. And i can not really predict the consequences or reaction of such a unconventional route. And i also do not want to freak out my new boss by mentioning this idea, if the majority of you would consider it as very inappropriate.

What are the pros and cons of extending your research field by doing a second PhD in another direction stead of deepening while doing a Habilitation in the same field?

EDIT: The current Position is in Germany. Although i would be interested in staying in Germany, i would also like to hear about perspectives on this for other countries. That also makes the value of the question more general.

  • @Maarten Buis. You are right, i edited the question to add this information. I am in Germany, but in general curious for implications of such a path in other countries to. Because later i might move.
    – Hjan
    Nov 16, 2017 at 16:04
  • 2
    If you can convince someone to be your advisor for a PhD you should be able to convince the same person to do research with you in the same field without doing a PhD. What is the point of having another PhD? If you want to show that you can do x and y, it should be sufficient to have published in x and y.
    – Mark
    Nov 16, 2017 at 17:17

2 Answers 2


As has been covered in other questions e.g. Is doing two PhDs a good path? or After PhD in Aerospace Engineering, could I be admitted into a top university for a second PhD in Computer Science?, there is rarely a need to pursue a second PhD to change fields. Once you have acquired the basic research competence, you can shift fields at any point in your career (as indeed you are already doing by publishing in a CS field).

Moreover, the volume of research required for a PhD thesis and a Habilitation is quite similar. Rather than going back and doing a second PhD, would it be possible to start pursuing more collaborations with the CS department and publishing CS research, so as to eventually obtain your habilitation in CS? Or interdisciplinarily with research from both fields, if you would like to keep your options open?

  • Shifting the field of publications is one thing, getting a position or funding is another. It was not easy at all to get a Post-Doc position in another field, even with some publications in the new field (but not of the same quality and quantity of a native PhD in the field). I think that such a situation is common for the few working on the border of 2 fields. The requirements for funded Post-Doc positions are obviously different that the requirements for a PhD Positions. The idea i am asking about is to have a position at one department, but do the PhD (or Habitation) in another.
    – Hjan
    Nov 17, 2017 at 10:52
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    Well, you're going to have to talk to your current department to figure out how much CS research you can do before they stop funding you (maybe not in quite those words). And talk to the CS department how much research you have to do before they start funding you. Hopefully there'll be a point where the two cross...
    – nengel
    Nov 17, 2017 at 12:57
  • Ofcourse should talk about this with the involved people. But since the idea is new, unusual, and because i am still new in the department, i was hoping to get some advises here in advance.
    – Hjan
    Nov 21, 2017 at 15:58

In Italy for example, if you have a scolarship for a PhD you can't do a second PhD with another scolarship. So you will work other 3 years without any refund.

  • The position is funded by a project. I am in Germany, but in Italy it could be for example the hypothetical situation that you will have an assegno di ricerca, or Ricercatore tipo A, for 3 years at an engineering faculty, but at the same time you try to do the doctorate, as an "external" PhD student at the Computer Science department (as if you were in industry, or a research center). The idea is to do the work and publications both for the Project of the funding and for the second PhD.
    – Hjan
    Nov 16, 2017 at 16:11

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