New APAM Faculty: Aron Pinczuk and Horst Stormer
Two Lucent Scientists Join Columbia, Will Research Condensed Matter
The Record, Vol. 23, No. 22
By Bob Nelson
At temperatures that approach absolute zero and in strong magnetic fields, electrons start to behave very strangely. As carriers of electric current, they appear to possess only a fraction of their normal charge. They can be made to travel as waves in quantum wires, and can be bound into new, artificial atoms called quantum dots. They can even enter superfluid states where they seem to move without friction or resistance.
Two new tenured faculty at Columbia, Aron Pinczuk and Horst Stormer, are exploring these and other behaviors as they research the fundamental properties of semiconductors. The pair have conducted their research at Bell Labs, the research and development arm of Lucent Technologies Corp., and will remain affiliated with the laboratory.
Pinczuk is known as a leading experimentalist of inelastic light scattering in semiconductors and Stormer as a co-discoverer of the fractional quantum Hall effect. Each accepted a joint appointment in the department of physics and the department of applied physics effective Jan. 1, and will be known as “professor of applied physics and physics.”
Both work in the field of condensed matter physics, the study of condensed phases of matter such as solids and liquids. The field has grown into the largest specialty within physics, with tremendous intellectual and technological importance. The two new faculty members add important new strength to Columbia’s program in condensed matter physics and material science and will begin teaching advanced physics topics in the fall 1998 semester at both the graduate and undergraduate levels.
It is the unique properties of semiconductors, the materials from which transistors are made, that lie at the heart of the computer revolution. Millions of interconnected transistors, each switching on and off hundreds of millions of times per second, provide the semiconductor “brain” controlling desktop personal computers as well as the fastest supercomputers. At present, semiconductors are used to switch electric currents, but a new generation of optoelectronic materials is being developed that can switch light instead of electricity, offering even higher levels of speed and miniaturization.
The two physicists are investigating the fundamental properties of modern semiconductor structures, research that may eventually help create improved electronic devices such as computer chips or optoelectronic devices such as solid-state lasers. Their research focuses on structures at the scale of nanometers, or billionths of a meter, that are only a few hundred atoms across.
“We are extremely pleased to have, in Aron Pinczuk and Horst Stormer, two brilliant new lights to add to the physics and applied physics departments at Columbia,” said Zvi Galil, dean of the Fu Foundation School of Engineering and Applied Science at Columbia.
Pinczuk and Stormer study systems in which the current-carrying electrons do not move in all three spatial dimensions throughout the material but are confined to an extremely thin two-dimensional layer or one-dimensional line only a few hundred atoms thick. Electrons can be so confined by building up the semiconductor material in layers in such a way that one layer is different from the rest. This special layer provides a small attraction to the electrons as they move through the material. As the temperature is lowered, moving electrons have less energy and tend to occupy only quantum states located very near the special layer, finally abandoning all other quantum states at temperatures near absolute zero.
Electrons forced to move in such confined structures display new, unexpected behavior, especially if a very intense magnetic field is applied. For example, such confined electrons display a new sort of electrical resistance that is precisely quantized into steps. This strange behavior implies that the fundamental current carriers are no longer individual electrons but instead electrons that as a group carry precisely a third to a fifth of the normal electronic charge. Stormer and colleagues were the first to observe this effect, called the fractional quantum Hall effect.
Stormer observed the fractional quantum Hall effect by electrical transport—simply measuring the flow of electrical current—while Pinczuk used a different method, in elastic light scattering experiments. Pinczuk developed light scattering methods to study low-dimensional electron systems. Such experiments have uncovered new behaviors that emerge when electrons condense into exotic liquids.
World-Class Physicists Join SEAS Faculty
Columbia Engineering News
Two condensed matter physicists whose groundbreaking work is admired worldwide have accepted tenured faculty positions. Aron Pinczuk and Horst Stormer, physicists at Lucent Technologies, accepted joint appointments to the School's Department of Applied Physics and to the Department of Physics.
Dr. Pinczuk is known for his experimental work in nanostructure optics and Dr. Stormer is the co-discoverer of the fractional quantum Hall effect. Both are enthusiastic about their new affiliation with the University and look forward to helping the University develop a mutually beneficial relationship with Lucent Technologies.
"We are working at the interface of fundamental physics and novel applications," said Dr. Stormer, "so our work is of interest to both Columbia and Lucent. We can participate in both worlds, and bring them closer together." Dr. Pinczuk echoed his colleague's sentiments, saying that both of their research areas have future industrial applications for electronics and photonics.
While their areas of specialization are different, it is clear that the ease with which Drs. Pinczuk and Stormer discuss their move to Columbia and their continued affiliation with Lucent comes from years of being close colleagues.
Speaking with them is like watching a fast-paced basketball game. If you imagine the ball bouncing back and forth between two players racing down the court, you have a good picture of a conversation with the two physicists. As one barely finishes speaking, the other has picked up the thought and expanded it, while the original speaker then seamlessly continues the conversation.
They joined Lucent Technologies at the same time and could watch how fundamental discoveries in materials science, optics and electronics changed the world. "Light wave communications did not exist 18 years ago," said Dr. Pinczuk. "When we came," continued Dr. Stormer, "it was all copper wires and amplifiers, and now the long-distance net is 99% fiber optics. The Internet would have been impossible back then."
"Within the last few decades," Dr. Stormer said, "we have seen the size of electronic devices reduced to a level where, on an 81/2 in. x 11 in. image of a device, one can recognize the individual silicon atoms from which it is made. Future electronic devices may well consist of individual molecules.
"Some of the research they had performed 15 years ago has now found its way into applications. "What we are doing now is fundamental research that will be applied within the next 10 to 20 years. It's a high risk-high reward enterprise," he continued. "In the best tradition of I.I. Rabi and Columbia's early work in the Radiation Laboratory," said Dr. Pinczuk. "We will be doing our research in academia and industry.
"Both scientists maintain their connection with Lucent Technologies by remaining part-time employees and keeping research facilities at this world-renowned industrial research laboratory. Space is currently being refurbished in the Schapiro Center for Engineering and Physical Science Research at Columbia to house the equipment that is required to perform their high-tech research on campus. Department Chair Gerald Navratil views the arrival of Drs. Pinczuk and Stormer as a great opportunity for the Department. "Their being here means a tremendous increase in our capacity in the area of solid state physics. It is a catalyzing step change and will provide the breadth in this important area of applied physics research that we have been lacking." "We hope and expect there will be strong cooperation between Lucent Technologies and the School," he continued, "so our students and the technical staff at Lucent can move freely between the two places."
Their arrival also is expected to invigorate interdepartmental efforts in materials science and solid state physics. Departments involved in this effort include Applied Physics, the Henry Krumb School of Mines (which runs undergradu ate and graduate programs in materials science), Electrical Engineering, and Chemical Engineering and Applied Chemistry. The two new faculty members will be involved in creating new solid state and materials science courses and will offer special seminars on the graduate level.
Dr. Pinczuk received his Licenciado in Physics from the University of Buenos Aires in 1962 and his Ph.D. in physics from the University of Pennsylvania in 1969. He was a visiting scientist at the Max Planck Institute and at IBM's Thomas J. Watson Center before joining AT&T Bell Laboratories. He is the recipient of the 1994 Oliver E. Buckley Prize of the American Physical Society, holds an honorary doctorate from the Universidad Autonoma of Madrid and is a fellow of the American Physical Society.
Dr. Stormer, who was appointed Director of the Physical Research Laboratory at AT&T Bell Laboratories in 1992, received his B.S. degree from the Goethe University in Frankfurt/Main, Germany in 1970. He received his Ph.D. in physics from the University of Stuttgart in 1977 and worked in the high field magnet laboratory of the Max Planck Institute in Grenoble, France. He is a co-recipient of the 1983 Oliver E. Buckley Award of the American Physical Society, a recipient of the Otto Klung Physics Award of the Free University of Berlin, and is a fellow of the American Physical Society and the American Acad-emy of Arts and Sciences.