DOE Physicists at Work
Profiles of representative DOE-sponsored physicists
doing research at universities and national laboratories
Compiled by the Office of Scientific and Technical Information
Dr. Zahid Hasan
"As a child my first wonder about science came about by playing with a compass needle - something invisible pulling it along a line - an invisible force at play," says Dr. Zahid Hasan, Assistant Professor of Physics at Princeton University. While the young Zahid Hasan, in attempting to understand the mystery, broke the compass into pieces, the rule of the game remained the same. "There was this mysterious and invariant force at play - and this same sense of mystery and search for the underlying fundamental law of nature seems to continue to drive my research today," says Dr. Hasan. "What are the quantum laws of nature that govern the physical property of complex materials? This sense of unraveling a mystery - that a tangible universe can be described by invisible forces and abstract rules, inspired me to pursue physics.
"In college, I have been lucky to have taken the quantum mechanics series from Steven Weinberg, where I was fascinated by the beautiful mathematics of angular momentum of spins," says Dr. Hasan. "Much of what I do today is understanding how electrons move through complex arrays of spins in novel materials using high-energy scattering techniques." His formal interest in condensed-matter quantum physics grew early in graduate school largely through conversations with Malcolm Beasley and Robert Laughlin at Stanford University. Equipped with a theoretical background, he then embarked on an experimentally challenging thesis, working with Zhi-Xun Shen, a leading expert in high temperature superconductivity and high-energy accelerator based spectroscopy. While a fourth-year graduate student at Stanford, he led an international collaboration with researchers from SLAC, Bell Laboratories of Lucent Technologies, Ames National Laboratory and Tohoku University in Japan that showed the feasibility of performing a new class of high-energy scattering experiments in condensed-mater physics which allows one to measure quantum numbers of electrons in complex materials.
In 2002, Dr. Hasan joined Princeton University as a Robert H. Dicke fellow in fundamental physics and was quickly promoted to assistant professor in physics. "I feel privileged to have the opportunity to continue my work at a world-leading institution that has distinguished itself in physics over the years," says Dr. Hasan. "My research is focused to use high-energy synchrotron x-ray and neutron scattering techniques to understand the quantum rules of the game that leads to fascinating materials properties such as high temperature superconductivity, large thermoelectric power, or quantum antiferromagnetism with focus on materials that exhibit triangular lattice symmetry," continues Dr. Hasan. "Theoretical works by Philip W. Anderson and N.P. Ong instigated my interest for exploring the wonder-world of triangular doped Mott insulators in search of new states of matter." The experimental techniques used in research are Angle- resolved photoemission spectroscopy, first explained by Albert Einstein, and inelastic (resonant) x-ray scattering, first demonstrated by A.H. Compton. "The modern developments in DOE laboratories such as Lawrence Berkeley Lab, Argonne, SLAC and Brookhaven allow one to measure the quantum numbers in complex materials which eventually provide clues to their unusual but remarkable useful properties," says Dr. Hasan.
Understanding the physics behind doped Mott insulators is the key paradigm to develop quantum materials relevant for modern technology beyond semiconductors, according to Professor Hasan. "Understanding of semiconductors led to the Silicon revolution - they are understood within the conventional tools of quantum mechanics. However, doped Mott insulators seem to go beyond such descriptions and hold enormous potential for fascinating properties. Hopefully their understanding will bring in new revolutions in technology leading to a new era of computing." The researchers are also developing new tools to address the challenges of understanding the new quantum rules. "These new tools will enable us to measure quantum numbers not previously accessible with existing techniques, and shed new light into the wonder-world of complex materials," says Dr. Hasan.
He adds: "I am also a new father. I'll be happy to support my daughter and son in whatever they choose to do later in life - but I think we'll definitely get them a fancy compass for their birthday."
Dr. Zahid Hasan's articles accessed via OSTI: