The University of Tokyo-based research group has developed a new technology that reduces the operating time to 40 picoseconds in switching elements used to transfer information in computers and electronic circuits. The structure, prepared with antiferromagnetic Mn₃Sn material, offers permanent switching that maintains its state even when the power is turned off, and operates with very low power consumption. The research results were published in the journal Science under the title Picosecond ultralow-power switching device based on an antiferromagnet.
40 picosecond switching pave the way for new generation computers. The research group, including Tsai Hanshen, Takuya Matsuda and Satoshi Nakatsuji from Tokyo University Graduate School of Science, worked together with Tokyo University engineering units, Solid State Physics Institute and RIKEN researchers. Using an antiferromagnetic material called Mn₃Sn, the team showed that the magnetic state, that is, binary data, can be changed with a very short electrical pulse of 40 picoseconds.
A picosecond corresponds to one trillionth of a second. Although processing power increases in current CPU and GPU architectures, one of the main problems on the data processing side is data movement between the memory and the processing unit. As processors and graphics processors become faster, reading and writing the needed data from memory does not become faster at the same rate. This situation creates a bottleneck called the memory wall.
The new work is not a ready-made product that directly replaces the processor core; It provides a basic component that can perform the switching process on the processor, memory and data movement side faster and with lower energy. In classical switching elements, as the speed increases, energy consumption and heat production also increase. Therefore, operating times below nanoseconds constitute an important limit in terms of practical use.
The system demonstrated by the University of Tokyo team is capable of switching at the picosecond scale, which is approximately 1000 times faster than the nanosecond scale. It achieves this through spin-orbit torque, which uses the spin movement of electrons, instead of a heat-based mechanism. This structure combines high speed and low heat production under the same roof. A thin film structure consisting of Mn₃Sn and tantalum layers was used in the research.
The team prepared a Hall bar-type element by combining a 10- to 16-nanometer-thick Mn₃Sn layer with a 5-nanometer Ta layer. The anomalous Hall effect was used to read the magnetic state. In addition, optical pulses in the 1.55 micrometer communication wavelength band were converted into 60 picosecond current pulses via a high-speed photoelectric converter, and switching was possible with these pulses. Error-free switching was observed in 250 repeated tests.
The remarkable part of the study is not only the speed. Researchers calculated the energy density to be approximately 1.7 pJ/µm² and the power density to be approximately 0.04 W/µm² for a 40-picosecond drive. This value means consumption of approximately 1 fJ for a 1-bit element of size 30 nm × 30 nm × 10 nm. The team also demonstrated that switching could be done more than 10¹¹ times with picosecond pulses. This provides much higher robustness than other picosecond switching methods such as phase change or filament formation.
The new technology also offered a fundamental demonstration of spintronic photoelectric conversion, in which the optical signal can be converted to an electrical signal and directly coupled to non-volatile memory writing. This point is especially important in reducing the power consumption of input-output lines and memory access in data centers. In the next stage, the research team focuses on improving picosecond level operation, circuit design and application conditions that do not require an external magnetic field.
The research team wants to move this technology to a practical prototype chip level by 2030. Nakatsuji states that if the technology is applied, data processing processes that take hours can be reduced to much shorter times.
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