A Bangladeshi scientist leads the discovery of a new quantum state of matter

A Bangladeshi physicist led an international research team to discover a new quantum state of matter that can be "tuned" at will and is 10 times more adjustable than existing theories can explain.

Dr. Zahid Hasan of Princeton University in the United States said that his team's discovery of this level of quantum material manipulability opens up enormous opportunities for nanotechnology and next-generation quantum computing.

"We expect it to be the tip of the iceberg," he said. "There will be a new subfield of materials or physics from this. … This would be a fantastic playground for engineering at the nanoscale.

Hasan, former Dhanmondi Government Boys High School and student at Dhaka College, became famous in 2014 when he led a team of scientists who finally discovered "The Weyl Fermion".

The existence of the massless elusive particle was predicted in 1929 by physicist Hermann Weyl, a colleague of Albert Einstein at Princeton, while pursuing an alternative theory of gravity.

Hasan and his team call their discovery a "new" quantum state, because it is not explained by existing theories on the properties of materials, reports the UNB.

"This has implications for nanotechnology research, especially for sensor development," he said.

The groundbreaking research, "giant spin-orbit and anisotropic tunability in a highly correlated kagome magnet," appears in the latest issue of the scientific journal Nature.

In this article, Hasan said that he and his colleagues found a strange quantum effect on the new type of topological magnet that can be controlled at the quantum level.

"The key was to look not at individual particles, but at the ways they interact with each other in the presence of a magnetic field," Hasan said.

"Some quantum particles, like humans, act differently on their own than in a community. You can study all the details of the fundamental principles of particles, but it is impossible to predict the culture, art or society that will emerge when you assemble them and start interacting strongly with each other.

Quantum culture

To study this quantum "culture", he and his colleagues arranged atoms on the surface of the crystals according to many different patterns and looked at what had happened. They used various materials prepared by collaborating groups in China, Taiwan and Princeton.

One particular arrangement – a six-fold honeycomb shape called "kagome trellis" for its resemblance to a Japanese weaving pattern – has led to something surprising.

All the known theories of physics predicted that the electrons would adhere to the underlying six-fold model, but the electrons hovering over their atoms decided to walk to their own drummer – in a straight line, with double symmetry.

"The electrons have decided to reorient themselves," Hasan said. "They ignored the symmetry of the network. They decided that jumping this way and that way, in one line, is easier than on the side. So, that's the new frontier. … Electrons can ignore the network and form their own society.

This behavior was only visible when the spectromicroscope examined it in the presence of a strong magnetic field.

"The researchers were shocked to discover this dual arrangement," said Songtian Sonia Zhang, a postgraduate student at Hasan's lab and third co-lead author of the newspaper.

"We expected to find something six times, like in other topological materials, but we found something completely unexpected. We continued to investigate and found more unexpected things. It's interesting because theorists have not predicted it at all. We just found something new.

Hasan said that although scientists can calculate many things based on the existing theory of quantum materials, the team's paper is exciting because it shows an unknown effect.

"The fact that we have found a material with such a high g factor, which means that a modest magnetic field can have a significant effect on the system, is highly desirable.

"This gigantic and tunable quantum effect paves the way for new types of quantum technologies and nanotechnologies."

The discovery was made using a two-stage, multi-component instrument called the Tunnel Spectromicroscope, working in conjunction with a rotating vector magnetic field capability in Hasan's laboratory, located in the basement of Jadwin Hall in Princeton.

The spectromicroscope has a resolution less than half the size of an atom, allowing it to scan individual atoms and detect the details of their electrons while measuring energy and spin distribution.

From Dhaka to Princeton

Professor M Zahid Hasan did his SSC at the Dhanmondi Government Boys High School and the HSC at Dhaka College, achieving remarkable results.

He studied at the University of Texas at Austin and obtained his Ph.D. at Stanford University before joining Princeton.

Now a physics professor with a special interest in the field of quantum condensed matter physics, Hasan worked in the revolutionary subfield of topological materials and led the discovery of topological quantum magnets a few years ago.

His research interests include Physics Today, Nature News, Science News, New Scientist, Scientific American, and Physics Worlds. It has even been listed in the world's most influential scientific minds by Thomson Reuters in 2014.

One of the other two co-authors of the new article, postdoctoral research associate Jia-Xin Yin, said he had been attracted for the first time by Hasan's interest in operating beyond the limits of known physics.

Yin said his interest was stung when Professor Hasan had announced that he was looking for new phases of the material, but that the question underlying the research was still undefined.

"He told me something very interesting," Yin said. "He said that what we need to do is look for the question rather than the answer."

David Hsieh, a physics professor at the California Institute of Technology, who was not involved in the research, said he was "excited" by this new discovery.

"This could indeed be evidence of a new quantum phase of matter," he said.

"They gave some clues that something interesting is happening, but a lot of follow-up work needs to be done, not to mention some theoretical support to see what actually causes what they see."