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Columbia Postdocs Named Finalists for Blavatnik Regional Awards

Dec 16 2019 | By Allison Elliott | Yankowitz photo courtesy of Matthew Yankowitz | Zang photo courtesy of Yaping Zang
Split image with on the left a portrait of Matthew Yankowitz and on the right a portrait of Yaping Zang.

While working in the Dean Lab, regional finalist Matthew Yankowitz (left) frequently collaborated with Professor James Hone’s group on research in two dimensional materials. Yaping Zang (right), a former postdoc in the Venkataraman Group, was recognized for novel techniques for single-molecule chemical reactions.

Two former Columbia postdocs working at the frontiers of quantum physics and single molecule chemistry were chosen as Finalists in the prestigious Blavatnik Regional Awards. Named for global philanthropist Len Blavatnik and given jointly with the New York Academy of Sciences (NYAS), the commendation recognizes outstanding contributions from early career scientists and engineers in New York, New Jersey, and Connecticut. Winners were honored this past November at the NYAS Annual Gala in New York City.

Matthew Yankowitz was recognized for his innovative experimental techniques with a class of two dimensional (2D) materials called van der Waal materials—layered combinations of super thin materials attached through weak interlayer interactions—of which graphene is a famous example. While a postdoc in the lab of Professor of Physics Cory Dean, Yankowitz also collaborated closely with Wang Fong-Jen Professor of Mechanical Engineering James Hone on investigations into 2D materials, particularly in the new and exciting area of “twistronics,” the study of twisted 2D materials and their properties. Now on faculty at the University of Washington, Yankowitz recently published a study on this research in Nature Nanotechnology.

Yaping Zang was commended for her novel techniques for producing electrically-driven chemical reactions that could pave the way for more sustainable chemicals synthesis for useful products. From 2016 to 2019, Zang conducted research in the lab of Lawrence Gussman Professor of Applied Physics Latha Venakataraman, a highly collaborative and interdisciplinary environment bringing together chemists, physicists, and engineers to investigate single molecule devices. Zang is now hiring postdocs of her own for her lab at the Institute of Chemistry at the Chinese Academy of Sciences (ICCAS) in Beijing.

Columbia Engineering spoke with Yankowitz and Zang about their research, what drew them to Columbia, and how the university’s highly collaborative environment advanced their scholarship.

Collaboration is one of the defining features of Columbia, especially in engineering and physics... There’s a ton of institutional knowledge and resources that you have access to through this type of collaboration.

Matthew Yankowitz
Assistant Professor of Physics (joint appointment in Materials Science and Engineering)

Matthew Yankowitz

Assistant Professor, Physics (joint appointment in Materials Science and Engineering); WRF Innovation Assistant Professor in Clean Energy
University of Washington

What brought you to Columbia for your postdoctoral research?

I’ve been working with a variety of 2D materials like graphene since I was an undergrad at Stanford. In my senior year, I worked in a lab doing pretty similar research to what I did at Columbia. When I was looking for postdocs, Columbia was particularly appealing as it is one of the top places in the world for research with 2D van der Waals materials.

I think collaboration is one of the defining features of Columbia, especially in engineering and physics. Cory and Jim had neighboring labs and basically an open door between them, so there was really no barrier to working in both labs. Many of the facilities were shared and students in both groups would sometimes even attend the other’s group meetings. There’s a ton of institutional knowledge and resources that you have access to through this type of collaboration.

What did your research in “twistronics” focus on? Why this has become such an important research area?

Cory and Jim developed an innovative technique about 10 years ago by which you could take isolated 2D crystals and stack them on top of each other. Upon doing that, the community quickly realized that the twist angle between the crystal layers can matter. If you change the twist, a geometric interference pattern called a moiré pattern arises, which can substantially modify the electronic properties of these materials. So effectively, two materials stacked on top of each other with a twist can behave very differently than the parent materials in isolation. By changing the twist angle, we can dynamically tune the electronic and physical properties of the device.

The field has really exploded since March 2018. There was a report from a group at MIT that if you take two layers of graphene and twist them at a “magic angle” of 1.1 degrees, then you turn the metallic graphene sheets into a highly tunable system which can be switched between a metallic state, an insulating state that’s driven by interactions between all the electrons in the system, and also a superconductor where, at low temperatures, the device can conduct electricity without any dissipation. Those could have potential future applications in energy efficient wires and other novel electronic devices for computing. One challenge is that so far this only happens at low temperatures; it would be great to find a way to also realize this at room temperature.

What’s your next big challenge in this area?

We’re still working to understand why there’s superconductivity in twisted bilayer graphene at all. There are still open questions about superconductivity, especially in certain exotic classes of materials. We’re potentially trying to use graphene to understand whether we can develop new theories for superconductivity that will help us design materials that might work at higher temperatures, although it’s not clear that this will be possible. The more interesting thing is that this system is very highly tunable and there are many different electronic phases with exciting new physics to which we now have access. That’s really the main focus of my research: trying to understand what new electronic states we can realize in these materials, how we can modify and control them dynamically within a single device, and whether we can eventually use this platform to build new device functionalities that currently don’t exist due to materials limitation.

Understanding how individual molecules interact with each other will inform the design of new materials and may even introduce new modes of operation for organic or molecular devices such as sensors.

Yaping Zang
Professor, CAS Key Laboratory of Organic Solids

Yaping Zang

Professor, CAS Key Laboratory of Organic Solids
Institute of Chemistry, Chinese Academy of Sciences (ICCAS)

How did you become interested in single molecule electronics?

During my PhD, I worked on designing and developing organic electronic devices using films of molecules under the guidance of Professors Daoben Zhu and Chong-An Di. I had always been curious about how the properties of individual molecules contribute to the behavior observed in organic materials and devices. Professor Latha Venkataraman’s group at Columbia has pioneered the research of interrogating the electronic properties of single molecule attached to metal electrodes through a scanning tunneling microscope. This drove me to join the Venkataraman group as a postdoc.

I have been fascinated by this research since running my first single-molecule conductance measurement at Columbia. I was really impressed by this technique since it enables one to repeat single-molecule measurements thousands of times in a very efficient manner and yields highly reproducible data.

During my time at Columbia, my research was very interdisciplinary and I worked closely with the Roy group, the Nuckolls group, and Dr. Steigerwald from the Chemistry Department. Working in interdisciplinary fields gives you unique strengths that can possibly lead to whole new ideas.

You’re working to advance environmentally-friendly production of industrially relevant materials. How does single-molecule research contribute to a more sustainable future?

Traditional synthetic chemistry often requires the use of costly or toxic chemical catalysts to speed up the reaction. Recently, there has been much interest in driving reactions electrically as a cheaper and greener alternative to traditional chemical synthesis. My research probes this question at the single-molecule level, providing deeper mechanistic insight and opening new avenues for electro-catalysis. Using a scanning tunneling microscope method, I demonstrated that it is possible to create new chemical products through an electrical field or electrochemically driven process. For example, I have found that we could couple two aniline molecules into azobenzenes, which are important industrially relevant materials, through electrooxidation.

I hope these methods can be developed into industry-scale techniques for producing commercially relevant materials in the future. In addition, understanding how individual molecules interact with each other will inform the design of new materials and may even introduce new modes of operation for organic or molecular devices such as sensors.

How did you come to your current position at ICCAS in Beijing?

ICCAS is one of the leading research institutions in China. Here, we have many well-respected and established researchers in various fields of chemical sciences. I got huge support from ICCAS to build up my own independent lab. On a personal side, I like to live in Beijing, a city with rich culture that’s also near my hometown.

It was really a wonderful experience to be at Columbia for three years and have the opportunity to work with great people and also make a lot of friends. Now life is quite different and it is a very exciting new journey for me. And of course, I am looking forward to visiting Columbia and meeting my friends again in the near future.