Talk with Mitali Banerjee, Professor, EPFL

What have been your primary field of research and your most surprising scientific finding during these last years ?

I am an experimental physicist working in the world of two-dimension of solid state, namely, conductors, semiconductors, and insulators, at ultra-low temperature close to the absolute zero, and under the influence of very high magnetic fields (thousand time stronger than that of earth). In the past few years, I have been focusing on system where the electrons interacts with each other strongly, thus leading to new states of matter that do not naturally exist in the world. Such systems are called topological systems, with one of the important system is the quantum Hall effect. The quantum Hall effect, lives in a two-dimensional electron gas, exemplify the earliest class of topological states of matter. The material is insulting but the edges are conducting. Moreover, one variation is called the fractional quantum Hall effects, where the electrons conspire to look to the observer as they have a fraction charge of the single electron. They are called anyons, and behave differently that electrons, photons, phonons, and other particles that we know in our three-dimensional world.  Moreover, a few of these exotic states in the fractional quantum Hall effect, are expected to host these fractional particles, but these particles are not localized in space to one place, but spread over a distance. Hence, they are not sensitive to a perturbation from the environment, which is usually taking place in on spot. Thus are promising to play an important role in quantum computations. Tom make things even more complicated some of these weird particles lost their charge, and thus, cannot be easily detected. However, by letting these particles to hit ‘potential walls’, they breakdown and produce an electronic noise that can be measured. During my postdoctoral studies at Weizmann Institute of Science in Israel, our experiments showed that unlike electrical conductance of charges ((electrons), heat conductance (of energy) of channels that are confines to narrow strips in the 2D worlds (1D channels) is universal and is independent of the nature of the particles (being electrons, photons, fractions, etc.), except in the case of the non-localized particles mentioned above. These experiments were path-breaking and attracted a lot of theoretical attention due to a long-standing debate over the very existence of the most elusive non-localized particles.

What is the coolest thing about your work/research ?

The coolest part was to prove in the laboratory important theoretical predictions as old as two and a half decades, but at the same time also disproving some dogmas. Above all, thermal conductance measurement not only compliments the electrical measurements, but rather can be a stand-alone probe to identify potential quantum states that can make the dream of topological quantum computers a reality. I mean, there are proposals for such computers for more than the last two decades, but the bottleneck was to first detect the particles that can be immune against the disturbance of the environment. My research goal is to identify the candidates that can potentially qualify these requirements. Namely, though I am not the one who is going to make such advanced quantum circuits for computers, my research focuses on acquiring fundamental knowledge of these exotic quantum states, being the first step towards the future realization of any such possibilities.

Where do you see yourself in 10 years ?

I believe we are in a golden era in terms of the availability of high-quality, high purity, materials, and world-class fabrication facilities, including state of the art measurement instrumentations. My experimental goals of studying the quantum-behavior of exotic particles may seem very difficult, but given present-day opportunities, I am very hopeful that it is the right time for my studies. Our daily life is fully technology-dependent, and somehow miniaturization of devices calls for more fundamental research. Not only understanding the electrical properties but also heat/or energy transfer is very important to keep up with the pace of the demands. Though 10 years is a long time, and with the fast-evolving nature of the field it’s difficult to predict the future, but I definitely wish to fully understand the topological states of matters without restricting myself in any one category of materials/platform. Rather I will try to establish new identifying experimental probes of known systems and use them to explore unknown realms of strongly interacting particles in solid matter.

From where comes your passion for physics ?

I am fascinated by the ideas of quantum mechanics, and as an experimentalist, being able to see things happening in the laboratory is the most exciting part. I like to explore challenging projects, which keeps me awake at night, and of course the number of failures I have so far faced, made me only more determined to pursue the goals with even more momentum. In short, I cannot imagine my life without physics, and now, that I am building a laboratory of my own, I dream of doing all that I always hoped, for and wish I can infuse my enthusiasm in my students as well.

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