Dr. Eduardo Cuansing, Jr. giving a lecture on electron-phonon interaction
by Quirino Sugon Jr.
Dr. Eduardo Cuansing Jr. is a new faculty of the Department of Physics of Ateneo de Manila University. He obtained his BS Physics degree from the University of the Philippines, Diliman and his PhD Physics from Purdue University. His undergraduate thesis was on non-Abelian Gauge theories and his doctoral dissertation was on critical phenomena. He did postdoctoral research work at the University of Pittsburgh on the theory of vortices in high-temperature superconductors and at the National University of Singapore on the quantum transport of electrons and phonons. He has recently moved to the Department of Physics, Ateneo de Manila University. This 5 August 2013, he will give a talk entitled, “Electron and phonon transport in nonequilibrium many-body quantum systems with dynamic forces and components.” Below is an interview with Dr. Eduardo Cuansing, Jr. by the Ateneo Physics News:
Question 1. What was your career track?
I studied in Tay Tung High School in Bacolod City. Actually, I passed in Philippine Science High School, but my parents did not allow me to go. I was also accepted in the Ateneo Chemical Engineering and Management Engineering programs, but I studied instead at the University of St. La Salle in Bacolod City.
I like science. I like to write. So I asked my self, “Why not Creative Writing?”After one year, I went to the University of Philippines-Diliman as a Creative Writing major. I was thinking of writing science fiction novels as a career, though I did’nt know yet that I needed to take Chemistry and Physics to do this. Then I met Prof. Yanga in Natural Science 1 in UP Diliman. He convinced me to shift to physics. After one year in Creative Writing, I shifted to physics and then finished my degree. I worked with Dr. Magpantay for my thesis on non-Abelian gauge theories.
I went to the International Center for Theoretical Physics in Trieste, Italy for the diploma program in high energy physics. After that I moved to Purdue University for my PhD. in Physics. In Purdue I did research on Statistical Mechanics and Critical Phenomena. Dissertation with Hisao Nakanishi. After that I moved to University of Pittsburg to work with Yadin Goldschmidt. I was a postdoctoral fellow and we were working on the physics of vortices in high Tc superconductor. I went back to the Philippines and taught at De La Salle University for two years and two trimesters. Then I went to the National University of Singapore. In the first two years I was at the Physics department working with Jian-Sheng Wang on thermal transport in quantum systems. After that I had another postdoctorate, but this time in Electrical Engineering with Albert Liang on electron transport in quantum devices. So finally, after three postdoctorate fellowships, I decided that it was time for me to go back to the Philippines and go to Ateneo de Manila University. Why Ateneo? Ateneo is semestral unlike DLSU which is trimestral. I prefer the semestral system. Ateneo is also close to UP; I can collaborate with people in UP. And the environment in Ateneo is a university setting compared to other universities. Academic setting is more conductive for thinking and doing research.
That is how I went from Tay Tung High School to Ateneo de Manila University. It is a long path. But you know, sometimes you go with the flow. You may also try to find your position, but sometimes you cannot prevent but just go with the flow. There are things that you cannot control.
Carbon nanotube transistor and a graphene transistor
Question 2: What research do you intend to work here in Ateneo?
Right now I am working on quantum transport in really small devices that are small versions of existing ones like transistors or RF receivers and things like that. I am also working on devices that haven’t existed yet, something new. I wish to study how electrons, phonons, or photons and other quantum particles would travel in these really small quantum systems, and how we can manipulate their motions. I wish to take advantage of their properties. Right now I am specifically looking at time dependent behavior of these systems. It is a hot topic. But normally what has been done is on steady state and not on time dependent state. That is, you let the system evolve for a long time and then study the characteristic of the system after this long time. This is the steady state of the system. But what I would like to study is really the real-time behavior of the system. For example, if you have a cellphone, there is a signal impinging on your device. That signal is time-dependent and not steady state. What is the physics of this time-dependent process? There are attempts to study this. It is a very difficult topic. It needs a long of hard work with the help of computers. One advantage for researchers nowadays is the existence of really powerful and cheap computers. We could take advantage of that. Problems that are difficult to solve 20 years ago we can now actually find a numerical solution using these powerful computers.
In quantum transport specifically, I am looking at electrons moving in a system where there are phonons which will carry energy as heat or internal energy. So when an electron interacts with a phonon, what happens? Will the electron slow down? Will they influence the phonons? Will they heat up? Can we make sense of these energies by doing computations? Can we direct energy to another place, to another part of the system? I also wish to find devices involving electron transport that haven’t been discovered yet. I guess the main title for what I am working is time-dependt quantum transport.
There are also questions if you have photons. Photons impinging on your system will interact with the electrons. What will happen to the electron? If the electron absorbs the photon, the electron will increase in energy. In these devices, there are energy barriers like the ones discussed in undergraduate Quantum Mechanics. When particles are moving into a barrier, you either get reflected or transmitted waves. If you have particles with high energy, the transmission is better compared to a particle with that of a slower one. If the particles have energy below that of the energy barrier, the particles can tunnel through; it is going to be difficult for the electron to pass. If you have a photon interacting with an electron, there will be more energy. What happens to things like these? If you shine light on this quantum system, what will happen? What if the light is time-varying? Can we control how the electron moves? Can we have photon-dependent transistors on nanowires?
Now, there is also the question of Non-equilibrium Thermodynamics and Statistical Mechanics. Students may be interested on the open questions on these fields. But solving these questions are more difficult since they are more mathematical. But we can make use of some empirical methods in quantum transport to construct theorems in non-equlibrium systems.
If a student is interested in both quantum transport and non-equilibrium thermodynamics, and he is also interested in computers, then he can apply numerical analysis and programming. Some mathematical problems that were difficult to solve 20 years like triple and multiple integrals can now be solved numerically. We can also apply computers when the system has disorder. There is no good way to analytically treat the system unless disorder is Gaussian, which is not interesting. Computers are actually actually the best used when there is disorder. If you are just interested in theory, then you can also do this.
Question. 3. What are the system requirements for the computers that you need?
Nowadays, we have powerful computers that are cheap, such as quad core I7 costing about Php 30,000. This computer has four processors that are active which you can program in parallel, unlike five years ago when you only have a single core Pentium IV, unlike five years ago when you only have Pentium IV that has only one core. If you have a program, it is 3 gigahertz per CPU. With quad core i7, you can run four programs at the same time or run four calculations at the same time. The program is faster. It is not necessarily four times faster, but definitely faster than one computer alone. It all depends on the programmer.
Programming parallel computers is different from programming serial computers. It is really an art to make good parallel programs that are fast. This means the programs scale linearly with the number of processors. But if you have unlimited resources, you would want to have a supercomputer. But our resources are limited. So we use I7 and a Linux cluster consisting of desktop computers. The one thing nice is the software part: you can make a cluster just by using Linux, not with windows. The Windows OS is expensive and unstable. Linux is best when you want to do clustering of computers.
In my research I use Linux. And I use Fortran and C++ to write my programs. These have languages subroutines or libraries available in the internet that you can download. These libraries were programmed by experts in computer science, so they are really good. For example, if you want to program in linear algebra, it is numerically more efficient if you download the linear algebra package. This is written by computer scientists in University of Tennessee using Fortran 77. But you can use Fortran 90 to make calls to Fortran 77 libraries. You can also use C++ to call Fortran libraries. But just take note that there are differences. For example, in arrays, C++ counts from 0 to n-1, while Fortran counts from 1 to n. Thus, if you want to pass an array or matrix in C++ to Fortran, you must be careful with the language differences before interfacing them.
I prefer to use Fortran. There are libraries in Fortran. Translation is correct donw not have to make sure. But if you know how to program in C++, then you can learn how to program in Fortran. The Fortran compilers are included in Linux, so you don’t have to buy any compiler. I don’t do much graphics, unlike people in Atmospheric Science and Meteorology where they need good graphics. For may cases, we don’t deal with graphics that much. We only calculate integrals and solutions to differential equations for simulations of disordered systems. But for graphics, the requirement is not that high. We only need powerful number-crunching computers.
Question 4. What are you teaching right now?
Ps 52 for sophomore physics majors and Ps21 for sophomore computer science majors. Well, we only met for few weeks. So far the students are attentive and well-behaved. They participate in class. I like the students. But you know it is just a few weeks. The rest of the semester we will see how they would perform. But I think I have high hopes for the physics majors. They are really interested in physics. I am inspired to continue doing things more about physics, even if we are just in the sophomore level. So I try to add as many advanced physics flavors to the class. I am not requiring them to understand everything such as photons, general relativity, and quantum mechanics that we discuss in class but are not part of the syllabus. These are just flavors to get them more curious about advanced topics and learn more on their own, and hopefully inspire them to continue in physics.
The Computer Science students are also ok. I am interested in computing and I can relate to their interests. I am also interested in playing games. The students of this generation studied computers with ipad, iphone, and so on. Most of them are exposed to games. You cannot avoid to not to let them play games. In talking about projectile motion, I use the physics of Angry Birds. The question is this: how do you calculate the angle and height of the projectile? I told my students that they can write their own prototype of the Angry Birds game using the physics we are learning in class. I always try to relate physics to computer science and computing.
I am also teaching Classical Mechanics in Graduate School and in Undergraduate tutorials. So far, it is doing well. Classical mechanics is an important part of a physics student’s education. All the methods such as the Lagrangian, Hamiltonian, and the Principle of Least Action are also used in Quantum Mechanics, Field Theory, Electrodynamics, and Statistical Mechanics. This is just a tutorial course; maybe the department accepts more graduate students so we don’t have to give tutorials. Something must be done to promote the department to get more graduate students.
Question 5. What are your first impressions of Ateneo?
At least there are active research groups here, such as Photonics, Vacuum Coating, and Materials Physics Laboratories. I see students working during their laboratory meetings. They are actively talking about their research. That’s in the first floor of Faura Hall. I don’t know about the third floor. I think the ambiance is nice. If you are thinking about doing research in physics, the academic atmosphere makes makes you feel like doing physics, too. But the teaching can be time-consuming, such as when I prepared for teaching in the first two weeks, the teaching assignments changed; they are not set yet. The system is like that. Something can be done to improve the system. As a new faculty, I don’t have a syllabus. So I just ask a reference syllabus of other people, and construct my syllabus almost a day before the class. It is tough to to think about the syllabus, especially for a new faculty, of how things would progress during the semester. At this point, I don’t know what is going to happen, especially in the laboratory. I am a theorist. The laboratory is difficult for me. Now, I am designing an experiment, hopefully an experiment that is not too easy nor too difficult, because for a theorist all experiments are easy. Designing an experiment for a theorist is not trivial. I cannot really gauge how difficult an experiment is because I am a theorist.
Question 5. Any parting words?
Physics can actually be fun. If you are freshman, you study physics such as Newton’s Laws, Torque, and Statics. At some point, it can be boring if you just learn as much as you can. These are important concepts you learn on which you can build on. All knowledge is based on whatever was done before. Newtons laws–just learn them. When you go to advanced physics, the fun starts with Quantum Mechanics, Statistical Mechanics, Classical Mechanics, and Advanced Electrodynamics. The fun would start you explore cool ideas. And if you keep on, you proceed to graduate school and contribute to discovering new knowledge. The most rewarding thing about being a physicist is when you discover new knowledge and become the first person to realize that a particular system actually acts in a particular way. It is very satisfying feeling.
Also, everybody is curious, but physics satisfies that curiosity. If you have a system, you can be curious about what happens if you change this or change that. So you do an experiment or calculation. If you are an experimentalist, you change the parameters here and see what would happen, e.g. you lower the temperature. It is also possible to satisfy your curiosity if you are a theorist. You can do calculations. Let us say, instead of say , why not ? What happens to physics if you have ma plus a very small term? Would the physics of the universe change? Questions like these can satisfy by doing calculations. What is satisfying about physics is that you can satisfy your curiosity about physical systems.
So as a physicist, you don’t really consider work as work; it is mostly play—playing with ideas using computers and equipments. It is not really work. That is why when you meet a physicist, he will always work, typically always in the laboratory. Form him work ins not work but play. Pleasurable. Something you don’t really feel burdened to do. Enjoyable.
The only thing about being a physicist is that as a career, it is financially not that rewarding. If you become a professor, your salary is not that much. If you like physics, then doing physics is just like getting paid to play. If you really want to earn a lot, you can work in an industry or become a stock market analyst. The things that you learn analytically such as how to solve differential equations and how to construct equations for physical systems may be used here, but nobody has really successfully described the stock market very well. It is very a very difficult differential or integral equation. But people have tried. Success can be fifty percent. You can apply your analytical skills to financial markets and earn than those working in the academe.
Meeting of Filipino physicists at Trieste, Italy (May 2013). From left to right: Ernest Macalalad, Dr. May Lim, Dr. Francis Michael Ian Vega II, Dr. Eduardo Cuansing Jr., and Dr. Quirino Sugon Jr.