Phononics

According to Lei Wang and Baowen Li

We may, however, be about to turn “phononics” from a dream into reality. Specifically, researchers have recently built thermal diodes, thermal transistors and thermal logic gates, which are the basic components of functional thermal devices. Such components also raise the possibility that heat — long regarded as useless or harmful in electronic circuits — could be used to process information. Phononics would therefore add a new physical dimension to information processing in addition to electronics and photonics.

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According to Lei Wang and Baowen Li

Memory is an indispensable element for computer besides logic gates. In this Letter we report a model of thermal memory. We demonstrate via numerical simulation that thermal (phononic) information stored in the memory can be retained for a long time without being lost and more importantly can be read out without being destroyed. The possibility of experimental realization is also discussed.

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According to Lisa Zyga

“Like we explain in our Physical Review Letters article, all these logic gate functions can be achieved only when the system has the so-called negative or super response, by which we mean that the large temperature difference (change) will induce the small heat current,” Li said. “This is the so-called ‘negative differential thermal resistance.’” The NDTR phenomenon was also discovered by Li’s group in 2006.

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According to Patrick Barry

Concentrated heat normally tends to dissipate over time, which would seem to make heat-based memory impossible. But Li and Wang show that, under certain conditions, information stored as phonons can be preserved. Normally, heat flows faster when the temperature difference between two materials is greater, which is why a red-hot burner will heat a pot of water faster than a burner on medium. But the team previously showed that materials can be designed to work in the opposite way, so that a greater temperature difference causes heat to flow more slowly. This reversed response is what allows phonons at one of two temperatures — representing the “on” or “off” of digital memory — to stay at that temperature long enough to make the thermal memory useful.

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According to Baowen Li, Lei Wang and Giulio Casati

By coupling two nonlinear one dimensional lattices, we demonstrate a thermal diode model that works in a wide range of system parameters. We provide numerical and analytical evidence for the underlying mechanism which allows heat flux in one direction while the system acts like an insulator when the temperature gradient is reversed. The possible experimental realization in nano scale systems is briefly discussed.

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According to Baowen Li, Lei Wang and Giulio Casati

We report on the first model of a thermal transistor to control heat flow. Like its electronic counterpart, our thermal transistor is a three-terminal device with the important feature that the current through the two terminals can be controlled by small changes in the temperature or in the current through the third terminal. This control feature allows us to switch the device between “off” (insulating) and “on” (conducting) states or to amplify a small current. The thermal transistor model is possible because of the negative differential thermal resistance.

 

 

According to Robert F. Service

On page 1121 of this issue of Science, researchers report the first-ever set of simple devices, akin to diodes, that steer a small excess of phonons in one direction. If the effect can be improved, it could lead to a novel form of computation based on phonons and to heat-steering materials that make buildings more energy-efficient, among other things.

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According to Lei Wang and Baowen Li

Logic gates are basic digital elements for computers. We build up thermal logic gates that can perform similar operations as their electronic counterparts. The thermal logic gates are based on the nonlinear lattices, which exhibit very intriguing phenomena due to their temperature dependent power spectra. We demonstrate that phonons, the heat carriers, can be also used to carry information and processed accordingly. The possibility of nanoscale experiment is discussed.

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According to Phil Schewe

They suggest that thermal transistors (also proposed by Li’s group in Applied Physics Letters, 3 April 2006) could be combined into all the type of logic gates—such as OR, AND, NOT, etc.-used in conventional processors and that therefore a thermal computer, one that manipulates heat on the microscopic level, should be possible.

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