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Jun 21, 2023

The Physics behind Insulator

Most materials can be classified as either metals or insulators based on the behavior of their subatomic particles. Metals, such as copper and iron, have free-flowing electrons that allow them to

Most materials can be classified as either metals or insulators based on the behavior of their subatomic particles. Metals, such as copper and iron, have free-flowing electrons that allow them to conduct electricity. On the other hand, insulators like glass and rubber keep their electrons bound tightly and do not conduct electricity.

Resistive switching, a phenomenon where insulators transform into metals under the influence of an intense electric field, has intrigued scientists for its potential applications in microelectronics and supercomputing. However, the physics behind this transition, specifically the size of the electric field required, remains unclear.

Jong Han, a condensed matter theorist at UB, has led a study that takes a new approach to understand this ongoing mystery. The study, titled “Correlated insulator collapse due to quantum avalanche via in-gap ladder states,” explores the insulator-to-metal transition.

The difference between metals and insulators lies in quantum mechanical principles, particularly forbidden energy gaps in the energy levels of electrons. The Landau-Zener formula, developed in the 1930s, has been used to determine the electric field required to push an insulator’s electrons across these energy gaps. However, experimental results have shown that materials require a much smaller electric field than predicted by the Landau-Zener formula.

To address this discrepancy, Han focused on the behavior of electrons already present in the upper band of an insulator when pushed by an electric field. Computer simulations revealed that a relatively small electric field could trigger a collapse of the energy gap, allowing electrons to move between the lower and upper bands. This new understanding helps to explain some of the discrepancies in the Landau-Zener formula.

Additionally, Han’s simulation suggests that the quantum avalanche is not caused by extreme heat but is instead a result of the equilibration of electron and phonon temperatures. This finding indicates that electronic and thermal switching mechanisms can occur simultaneously.

The study also emphasizes the importance of fundamental research in materials science. Jonathan Bird, a co-author of the study, highlights that while the research aims to understand the physics of new materials, the electrical phenomena discovered could have implications for future microelectronic technologies.

Since publishing the study, Han has developed an analytical theory that aligns with the computer simulations. However, further research is needed to determine the exact conditions required for a quantum avalanche to occur.