Monday, February 11, 2013

Should I do a postdoc in the same topic as my Ph.D?

Breadth of experience is important; both for your development as a scientist and to demonstrate your versatility to potential employers. It should also be fun and interesting to work on something different.

However, a complete change of research field is not a good idea because the learning curve is so great meaning it is unlikely you will produce your first postdoc paper in a timely manner. (I recommend 6 months; others one 100 days).

It is a good if you can use some of the expertise, experience, and/or techniques you have developed in your Ph.D during your postdoc.

So on balance, here is my suggestion. Most projects involve applying a specific technique (experimental, computational, or analytical) to a specific system  (e.g., a class of materials or model Hamiltonians). A great situation is if you either:
use your Ph.D technique on a new system
apply a new technique to your Ph.D system.

For example, if you did a Ph.D using neutron scattering to study transition metal oxides do a postdoc using inelastic X-ray scattering on the same materials.
Or if you used an electronic structure technique (e.g. DMFT+LDA) to study iron pnictide superconductors to do a postdoc using this technique to study organic charge transfer salts.

Unfortuantely, I get postdoc applications which say in effect "I worked on obscure topic X in my Ph.D and I want to keep working on it for the rest of my life. I don't care what you are working on. But I am sure you will want to hire me..."

Everyone is different and every situation is different. There will always be exceptions to the above considerations, especially for the brilliant [not me or you!].
I welcome comments.


  1. This is a very important question and thanks for raising it. From my little experience, I can probably put a similar question: Will I be allowed to do a postdoc on a topic different from my PhD one?

    This is something not much in the applicant's hands. But first of all, why should an applicant would like to work on a different field? There could be several reasons :

    1. Quite disappointed with the impact of PhD work (mostly due to lack of recognition).

    2. His/her topic is no more hot now. Needs to work on something where most people are interested (definitely more chance to get higher citation).

    3. He/she had already had a topic in mind, but couldn't execute since the PhD problem was different.

    4. Or just to get into a fresh new life.

    Now even if we assume the student has the flexibility to switch his field, what a team leader can look for before he/she appoints
    the applicant.

    1. Why is the applicant interested in this new field?

    2. What can he contribute to this field?

    3. Does he carry some basic knowledge/insight that may be helpful while working?

    4. Will it risk my career if I hire a person who hasn't work before in/close to my research area?

    I guess many scientists possess the last thought of insecurity, even they have a big established group.

    I remember, I have asked someone whether I should apply for the position mentioned in his advertisement since my field doesn't match with his. He just blindly asked me to send my CV and thesis. After a week, he said that he doesn't find anything close to his current area. He could have decided that earlier, since I told him the same at the beginning.

    Another difficulty I found is that most of the people are not ready to take interviews. They just require three things: 1. CV, 2. List of Publications, and 3. Reference letters; just like a protocol. I personally believe that these three are not enough to judge the applicant's creativity and skill.

    Recently I got one fair suggestion from a nice guy. He said: if you want to join a group on a topic which has no connection to your PhD work, then spend some time on that topic or collaborate someone locally, and see if you can publish and apply for the position after that.

  2. reducedplanckconstant:

    For what it's worth, I have had three postdoc interviews, to work on three different topics (some graphene numerics, quantum Hall physics, and nonequilibrium systems) and was not expected in any of these interviews to know a single thing about the potential employer's field. I also emailed a (cold atoms) guy, as you did, and got a much more helpful response of "prior experience is by no means necessary, I will hire according to talent over experience. However in the event of a tie, I must go with experience"!

    I don't believe I misunderstood those interviews (I was offered the three, so it must have gone o.k.!)

    So, when I talk to student colleagues about job applications, I always emphasise that they should have a very good understanding of their own PhD, and the related literature, and the state of the field, and the broad, big questions in that field, and that the preparation for the interview should focus on this.

    But my experience is anecdotal, of course. I have 3.5 examples. Perhaps this doesn't align with the majority?

    I think what Ross said about being interested in changing fields for the sake of breadth and versatility seem to make sense. In your initial list of four reasons to change field post-PhD, I would give one the benefit of the doubt and go with that instead, perhaps wrongly. Though I suppose you can hardly blame someone for wanting to get out of their PhD field because it's no longer "hot". I can empathise.

    However, with a significant change of field, I am certainly not clever enough to have something even moderately ambitious out after 100 days. So Piers Coleman would be disappointed with me, I'm almost certain. I think Ross' 6 months is a lot more lenient, and depending on the field shift, could still be quite a challenge.

  3. Thanks Tony. I believe, people in the UQ are more open-minded.

    I have just spoken from my own experiences and noway it can give a picture of entire world.

    Ross is doing a great job through his blog articles. I think, many people should come up and share their experiences in this post.

  4. Thanks reducedplanckconstant.

    I would be very interested to know (this is a little off the track of the original post I suppose - sorry Ross), what questions people in the business of hiring do actually ask themselves. Your four suggestions are very interesting.

    For a mid-career person (no ongoing position, but in the business of hiring), I think the fourth question would be particularly pertinent, by necessity. So perhaps mid-career people would be more likely to go with the (ostensibly?) safe option of someone who did their PhD in the same field, which according to the post is perhaps not so good for the graduate.