The Physicist Who Bridged Size Differences

The Wolf Prize is the most prestigious scientific prize awarded in Israel, but since the year 2000, only ten Israeli scientists have received it. Some of them, like Ada Yonath, Avram Hershko, or Chaim Cedar and Aharon Razin, became renowned and received public acclaim. Others remained relatively anonymous to the general public, and are mostly known within the scientific community for their substantial contribution to their field. One of them is physicist Yoseph Imry, who recently passed away.

From the Armored Corps to nuclear science

Yoseph (Joe) Imry was born in Tel-Aviv in 1939. Both his parents were teachers: his father taught mathematics, physics, and electronics and his mother taught English and French. “The atmosphere at home encouraged science and acquiring knowledge,” Imry said when he received the Israel Prize in Physics. At school, he was drawn to the field of aviation and aeronautics and was convinced he would study engineering and become an aeronautical engineer. “I never thought I'd be a scientist,” he told the Weizmann Institute of Science website. Nevertheless, in a spur-of-the-moment decision, he chose to study physics in the direct-master’s degree track at The Hebrew University of Jerusalem, as part of the IDF’s Academic Atuda program. He said that he was an average student, but shined in his final exams, eventually graduating summa cum laude. In 1961, he enlisted in the IDF and was stationed in the Armored Corps. He started out as an artillery instructor, but was later – and suddenly – transferred to serve at the Nuclear Research Center, by the instruction of physicist Yuval Ne’eman, who had been impressed with Imry’s skills.

Imry completed his mandatory service at the Nuclear Research Center, and continued to work there as a civilian. The center’s director at the time was Israel Falach, and Imry chose him as his PhD advisor, though Falach was an experimental physicist and Imry was more interested in theoretical physics. In an interview for the Weizmann Institute website, he said that he decided to pursue a PhD following a lecture by a famous physicist. “I thought his whole concept was incomplete, and I was convinced that I had a new way of thinking about it, emphasizing small systems. The research community believed that such small – nano-level – systems were not important in physics. So I spent the next three years working on a paper contradicting that.”

In 1966, Imry received his PhD from the Weizmann Institute of Science, and pursued a postdoctoral fellowship at Cornell University in the U.S. Upon his return to Israel, Yuval Ne’eman offered him a position at Tel-Aviv University, where he worked and taught for 17 years. His groundbreaking research focused on the field of mesoscopic physics – which bridges between systems at small and large scales. 

From small to large

Many theories in physics provide good descriptions for processes, but only at a certain order of magnitude. For example, Newton’s laws of motion describe the movements of bodies in sizes useful for us. But if these bodies are very small, like a single atom, or their velocity is very close to the speed of light, then Newton’s laws no longer apply to them, and their behavior is governed by the laws of quantum mechanics.

Mesoscopic systems are small enough to be influenced by quantum phenomena, but large enough to be measured using conventional tools, like electrical current and voltage measurements. From his first paper in the field, in 1969, Imry proposed a method for conducting such measurements. But the technological means to perform these measurements were not available yet.

The substantial advancement of microelectronics enabled building increasingly smaller detection and sensing systems, which enabled bridging between the two worlds. One of the most prominent examples for such a bridge is the rapidly developing field of quantum computing. Such a computer requires bridging between the quantum phenomena at the basis of its computation and memory, and higher-order systems such as electronic systems for measuring the results of the quantum calculations. These types of developments are based on theories developed by Imry.

Imry’s research extended into different fields of physics, many of which were eventually combined to establish the field of mesoscopic physics. Among other topics, he investigated the properties of superconductivity, especially in systems where the phenomenon is not persistent, but alternately appears and disappears. He studied how this property is affected by temperature and by changes in system size.

He also studied phase transition processes, and how they are affected by changes in size. With colleagues, he developed a theory that explains the unique state of matter of glass, according to the electron dynamics of its atoms. His research further addressed phenomena of electrical conductivity and magnetic fields, and again – in the mesoscopic aspect – how such phenomena are affected by transitions from one order of magnitude to another.

“The interest and excitement provoked by mesoscopic physics in the last 20 years stemmed from the fact that in these intermediate mesoscopic scales (usually tens to tens of thousands of atoms in size), the system can be measured by regular macroscopic means (e.g., electrical measuring instruments), but the properties they unravel would dictate the microscopic laws, i.e., the same laws that govern atomic and molecular physics,” wrote Imry for the Journal of the Israel Academy of Sciences, upon joining the Academy in 2002. "[…] Mesoscopic systems provide us a laboratory in which we can test the fundamentals of quantum physics by performing experiments that are not too complicated.”

Ahead of his time

Imry was essentially one of the founders of the field of mesoscopic physics and one of its world leaders for many years. Many of his predictions regarding such systems were later validated, once technological progress made it possible. His numerous studies also laid the foundations for developments in nanotechnology and its applications. In 1986, he moved from Tel Aviv University to the Weizmann Institute of Science, and led the establishment of the Center for Submicron Research and the Department of Condensed Matter Physics.

Imry received many honors and awards for his research, including the Rothschild Prize (1996), the Israel Prize (2001), the EMET Prize (2006), and the Wolf Prize (2016). He was a member of the Israel Academy of Sciences and a foreign member of the U.S. National Academy of Sciences (from 2008). “Imry created, developed, and led fundamentals in [this] field of research, which is the foundation of present-day nanoscience and nanotechnology,” wrote the Wolf Prize committee. “He is a physicist of incredible foresight, sometimes years ahead of his time, whose research is at the cutting edge of a number of fields in physics.”

Translated by Elee Shimshoni