My Journey with Millie in Thermoelectrics

Gang Chen
Thermoelectrics Session, MIT Memorial

Thank you.

The Hicks and Dresselhaus papers were published in '93, which was the same year I got my PhD from Berkeley. I did not know anything about thermoelectrics, then. I joined Duke University as an assistant professor, and I was desperately trying to find funding. I was working on heat conduction in nanostructures and superlattices, and I was worried about the fact that they cannot conduct heat very well, which was bad for semiconductor devices.

Someone told me, “You know, what you are doing might have applications in thermoelectrics.”

In 1996, there was a Multidisciplinary University Research Initiative (MURI) topic in thermoelectrics.  That motivated me to look into what, precisely, thermoelectrics is.  The MURI call-for-proposals specifically cited Hicks and Dresselhaus papers. I started to learn what thermoelectrics was and the basics of the field and, more importantly, I learned that thermoelectrics needed materials with low thermal conductivity that still conduct electricity.  It seemed to be a pretty good match with my research interests.

I interviewed at UCLA, and so I got to know Kang Wang — and he connected me to Mildred Dresselhaus.  I remember, Professor Wang told me, “Millie already knows you” — because she had been reviewing my application materials for a fellowship.

But that's how I got into thermoelectrics. And we started to write a proposal, together.

You can see a copy of Millie’s edits to the proposal, here.  Notice that, rather than seeing red (bloody) essay marks, I saw black — because this was a fax!  This is because, at the time, I was at Duke. The fax is has the date and time: September 3rd, 1996, at 7:49 AM.  This is, of course, because Millie came into the office at (or, sometimes, before) 6:00 AM. And she got a lot done before everybody else showed up.  This is just one example.

With Millie, we were very lucky — both lucky because of Millie, and lucky because we got funding for MURI. That was, actually, my biggest funding, and it was the first funding I ever got. In fact, Millie and Kang Wang even entrusted me as the P.I. for the project!

Therefore, in '97, we started the MURI program. Millie came to California quite a lot, back then.  She came to Caltech, because she was a trustee of Caltech, and she came to all the meetings, there. And every time — I think the meeting would end around 2:00, and I would go to Caltech and pick her up and bring her to UCLA, and then we'd have group meetings.

Then, we would have dinner, and, after dinner, I’d drop her at the airport, because she'd always take a Red Eye back to Boston. And, the next morning, Gene would be at the airport to pick her up and take her to the office at MIT. And so, now, I always take a Red Eye back from West Coast, whenever I go there, and that’s the reason.

I started my work on thermoelectrics with MURI, and I continue, even today, to work in thermoelectrics. We started doing work on nanowires, with Oded and Taka, Kambe, and myself. And I collaborated, with Millie, researching quantum wells and superlattices. The first picture, on this slide, was actually grown by Kang Wang, and it shows the silicon-germanium superlattice.

We worked, through this program, to really understand the heat conduction in these nanostructures. And somehow, I think that, in the process, I impressed Millie — and she played a very active role in bringing me to MIT. So thanks (in large part) to her, in 2001, I joined the mechanical engineering department at MIT. And, by that time, our MURI program was winding down. Based on what we had learned in the MURI program, we decided that we should really explore bulk nanostructures. And the rest of the picture on the slide is actually the bulk nanostructure we were working on.

We started working on that — and while it’s been true that, over these past nine years, we've been funded by the DOE Energy Frontier Research Center, the concepts around 2003 and 2001 were actually funded by NASA.  We collaborated with Zhifeng Ren, who is a materials expert, and also with Jean-Pierre Fleurial at JPL. You can see that, in 2008, we made a breakthrough and wrote up a report, which was actually published as a paper in Science! Since then, a lot of people have decided to pursue research in this direction, as well.

Throughout the whole process, many of my students were working in thermoelectrics — and, in fact, they continue to work in thermoelectrics, today! Millie would serve on their PhD committees, and she’d give them advice, she’d give them post-docs, etc. I’ve provided pictures of some of the students, below.

When I became a director for the Solid-State Solar-thermal Energy Conversion Center, which is a DOE Energy Frontier Research Center, Millie gave me the most important advice. She said, “Gang, you should divide the Center into subgroups, and then you should make sure to go to every meeting, every month.”  She also volunteered to go to every subgroup meeting with me.

And she was right!  I soon found that following her advice made the management of a group really easy, because she and I knew everything and could always see what was happening.

After I took the department head position, she volunteered to help advise my students. And — I just want to share one example. Millie went to every meeting with me, and every one of the subgroup meetings.  But this one meeting, she couldn’t attend — so she wrote me an email:

“I did not get to this meeting today. I spent time with Maria after the meeting. I tried to be helpful to her in her career guidance.”

So, as you can see, Millie didn’t just help on the scientific side, she also provided career support for a lot of my students. And many of them are very successful.

And I just wanted to show a few pictures.

This was taken when I ran into Millie at Narita airport, and, before I said hello, I thought… this is so characteristic of Millie, I have to take a picture!  Because you can see, here, this was her luggage — and her luggage was always heavy and full of paperwork — and you can see that she was always correcting. She was always reading at the airport or on the road or, just, whenever she had a spare minute. So I captured this photo, and then, of course, I went over and said hello to her.

The next picture I want to show is — this is at the Kavli prize. I felt very fortunate that she invited me to be at that event, with her. But I wanted to show you this picture to emphasize her generosity. The Kavli prize — and also the Heinz prize, I believe — both came with prize money, and she donated all of the prize money. The Kavli prize is typically given to three people, but, that year, the nanoscience prize went to only one person: Millie. She donated the prize money to MIT, who used it to establish an award for a female faculty member.

This isn’t a picture, actually; it’s a video.  But I still wanted to share it. The EFRC Forum and Summit was running a video contest in 2011, so we created a short video called “Battle Against Phonons” and wound up winning a prize — “Best with Popcorn”!  Millie features a starring role in the video. You’ll probably also recognize Gene and a few other familiar faces.

Every time I talked to her after most business, she would said, “You need to take care of yourself.”  This was another example of her generosity. I remember, when I took over department head position, she told me, “Take good care of yourself.”

Millie and I continued to work together, and, in fact, I think at the end of January, this year, she was added, as an author, onto a paper about defects by Mingda Li — who actually is going to join the MIT Nuclear Engineering department in the coming January. As you can see, we are continuing to work on phonons, and the paper is under review. There’s a lot of exciting science going on, including one paper measuring phonon spectroscopy, the mean free path distribution, and, most recently, working on the localization.  This was actually a paper we wrote two years ago, and we're still revising it.

Millie is an inspiration for us all. I am thankful to be sharing all this with you.