For a long time, non-Hermi physics research has been mainly limited to optical and acoustic platforms, and its implementation on ultra-large-scale integrated circuit platforms has been in a blank state. However, the two types of platforms of optical and acoustic only cover two extremes of the spectrum, namely the optical band at extremely high frequencies and the acoustic band at extremely low frequencies.
Therefore, a lot of missing is missing about a large gap in the middle of the spectrum - the study of non-Hermi physics by the electromagnetic band, which greatly weakens its research breadth in the scientific field and its application scope in the field of engineering.
Previously, a very small number of research groups used discrete electronic components and microelectronic mechanical systems to realize non-Hermi physical electrical systems and explore their applications in the field of electricity. However, the physical size of this type of electronic platform has obvious disadvantages, such as poor scaling performance and very limited operating frequency. Therefore, scientists have been looking for electronic implementation platforms for non-Hermi physical systems with good scaling performance, wide coverage spectrum range and high integration.
At the same time, in the field of microwave signal regulation, it is extremely challenging to achieve on-chip broadband microwave signal generation and non-reciprocal microwave signal propagation (unidirectional propagation). For a long time, achieving broadband non-reciprocal microwave signal propagation has been the long-term goal pursued in the RF/mmW chip design field.
Traditional methods usually use ferromagnetic material to achieve this goal, but ferromagnetic materials are both expensive and occupy a huge volume, and are also incompatible with semiconductor manufacturing processes. Therefore, it is extremely important to explore microwave non-reciprocal devices that can achieve fully integrated on-chip.
Figure丨Full-integrated silicon-based chip-level microwave non-Hermi physical system (Source: Nature Nanotechnology)
Recently, Washington University in St. Louis, USA Teams in Nature Nanotechnology and Scientific Reports published a paper by discovering non-Hermi physics and integrated circuits The complementary characteristics of technology have very cleverly solved two key problems in the fields of non-Hermi physics and microwave signal regulation, which can be said to be "killing two birds with one stone".
On the one hand, the team relies on modern ultra-large-scale integrated circuit technology to design the on-chip circuit necessary to form a non-Hermi physical system by using the very mature integrated electronic device , and realizes the first fully integrated silicon-based chip-level microwave non-Hermi-based non-Hermi-based for the first time meter physical system.
On the other hand, they used the non-Hermi physics to enhance the nonlinearity of the system, and used the non-ideal characteristics that were generally possessed by integrated electronic devices, realizing the function of on-chip broadband non-reciprocal microwave signal propagation.
has laid a good foundation for studying the topology properties of chip-level higher-order non-Hermi physical electronic systems
html l3The study began with a paper published in Nature Nanotechnology, titled "Fully integrated Parity and Even Time Symmetric Electronics" parity–time-symmetric electronics)[1]. The first author of the paper and the corresponding author of is . Cao Weidong, a doctoral student in the Department of Electrical and Systems Engineering at Washington University in St. Louis. The co-corresponding authors include Professor Yang Lan and Professor Zhang Xuan of the Department of Electrical and Systems Engineering at Washington University in St. Louis.
"This study demonstrates the feasibility of using modern integrated circuit technology to achieve non-Hermi physical systems. This breakthrough has opened up a new platform for the research of non-Hermi physics, and also provides research on integrated topological electronics. A bright prospect." Cao Weidong said.
Figure丨Related papers (Source: Nature Nanotechnology)
In the field of condensed matter physics , there is a strange thing The material state - its surface is in a conductive state, but the interior remains insulated. This property is different from the conductive and insulators that people know, so it is called " topological insulator ".The unique material properties of
This unique material properties have great scientific significance and application value. They can be used in a series of important technical fields such as wireless communication , radar and quantum information processing. Advanced-order non-Hermi physical systems have rich topological properties, and this breakthrough of the team has laid a good foundation for studying the topological properties of chip-level higher-order non-Hermi physical electronic systems.
Picture丨Cao Weidong (Source: Cao Weidong)
Along this direction, on August 4, the team was in S cientific Reports reports the phenomenon of discovering circuit topological properties during the post-simulation stage of the physical layout of integrated circuits. The title of the relevant paper is "Fully integrated topological electronics" [2].
Figure丨Related papers (Source: Scientific Reports)
integrated circuit physical layout are different physical layers in the chip manufacturing process, such as metal layers, A diagram of stacking a series of layers such as oxide layer and semiconductor layer, and wafer The factory implements streaming based on this physical layout. Therefore, the publication of this paper marks a big step forward to chip-level non-Hermi topological electronic systems.
On the other hand, This research has laid a strong practical foundation for the cutting-edge theory of non-Hermi physics to be put into engineering applications. Current research shows that nonlinearity in non-Hermi physical systems will be enhanced and will lead to the non-reciprocal transmission of light or sound waves. Instead, non-reciprocity can ensure the single propagation of waves and have very important applications in wireless communications and superconducting quantum circuits.
However, implementing fully integrated non-reciprocal microwave devices is a relatively difficult task. The mainstream on-chip implementation method today is to use time modulation, which requires the use of a large number of integrated capacitive inductor devices, thus consuming a lot of valuable on-chip area.
Cao Weidong said that "Our chip-level non-Hermi physical system just takes advantage of the nonlinearity that integrated electronic devices generally have. With very few on-chip resources, it realizes the function of broadband non-reciprocal microwave signal propagation. ”
Figure丨A diagram of the theoretical model and its equivalent electronic circuit model (Source: Scientific Reports)
The design inspiration for this research comes from The collision of thinking in cross-fields. Professor Yang Lan is a world-renowned scientist in the field of non-Hermi physical and optical. His team has been deeply involved in this field for many years and has a rich theoretical and experimental accumulation. Professor Zhang Xuan’s team has accumulated rich experience in the field of large-scale integrated circuit design.
By chance, Professor Yang Lan explained to Professor Zhang Xuan the principle of implementing non-Hermi physical systems on an optical platform, and shared that there are already research groups that use discrete electronic components to implement such systems. Afterwards, Professor Zhang Xuan was deeply inspired and inspired, and immediately decided to work with Professor Yang Lan's team to explore the implementation of fully integrated silicon-based chip-level non-Hermi physical systems and their major applications in the engineering field.
Figure 丨The characteristic frequency and phase change of a fully integrated polarization state parity-time symmetric electronic system of coupling factor evolution (Source: Nature Nanotechnology)
This study The biggest challenge lies in the on-chip circuit design and implementation stage. Cao Weidong recalled: "Professor Yang Lan gave a lot of theoretical help, which allowed us to quickly enter the system design stage."
, but he still encountered many setbacks when it was truly implemented in the circuit implementation and successfully tested the chip. The first difficulty lies in how to choose a broadband gain generation circuit. The team initially chose op amp to achieve this goal, but the team found that its stable bandwidth could only reach megahertz.Later, after multiple research and discussion, they found the circuit we are using now, namely, the cross coupled pair, which can generate gain at very high frequencies.
Figure丨Illustration and characterization of fully integrated PT symmetric electronic system (Source: Nature Nanotechnology)
The second difficulty lies in the selection of circuit structure. In the initial stage of the research, the team believed that implementing a single-ended circuit was simple and could save on-chip resources, so they adopted it as the main structure of the system. But to their surprise, this actually reduces the reliability of the system.
" After the first time I came back, I tested it, and the chip showed no sign of working. After checking countless times and confirming that it was not a problem with the use of the circuit design and process library, we decisively adopted differential circuit design to improve the system reliability. Finally, after The second fission test was successful. "Cao Weidong said.
is expected to be used in on-chip ultra-high sensitivity sensing, high-efficiency wireless energy transmission, etc.
Talking about the possible applications of fully integrated non-Hermi physical integrated electronics and technologies, Cao Weidong said, "In addition to the non-introduction mentioned in the research." Reciprocal microwave signal propagation and broadband microwave signal generation can also play an important role in on-chip ultra-high sensitivity sensing, high-efficiency wireless energy transmission, etc. "
, and fully integrated non-Ermi based on this technology Physical topological electronics will also bring many applications. Previously, studies have shown that chip-level integrated electromagnetic topological insulators can be used in the field of wireless communications.
The team believes that this technology will be applied in more fields in the future, such as extremely low noise microwave signal generation, superconducting qubit reading and regulation, etc. Next, they plan to design an integrated topological electronic system for slice verification and demonstrate its practical application in subsequent research.
Picture丨Photography of some members of Zhang Xuan's research group (Source: Cao Weidong)
It is reported that Cao Weidong's undergraduate and master's degree graduated from Tsinghua University and respectively ml3Northwestern Polytechnical University , its research backgrounds intersect in large-scale integrated circuit design and integration Circuit design automation, computer architecture and quantum computing . Currently, he studied under Professor Zhang Xuan in and is studying for a doctorate in the Department of Electrical and Systems Engineering at Washington University in St. Louis. His main research direction is in new computer architecture, focusing on accelerator design in specific fields.
He said, "In the future, I want to focus on major issues in the fields of integrated circuit design and computer architecture, such as the automation design of analog and RF integrated circuits, the design and implementation of high-performance computer architectures and low-temperature superconducting quantum control reading circuits, etc. ”
Its tutor Professor Zhang Xuan’s team is dedicated to research in interdisciplinary fields such as integrated circuit design and automation, computer architecture and micro autonomous robots. According to reports, the laboratory's recent research results and projects include: using near-sensing computing technology to achieve intelligent vision that integrates perception/inductive computing/perception fusion; using digital-analog hybrid computing and near-memory computing to achieve high energy efficiency and low energy consumption terminal and cloud systems; use software and hardware collaborative design and hardware acceleration to achieve energy consumption/safety/reliability optimization of large recommended systems; and use deep learning to achieve high-quality and efficient simulation and RF integrated circuit automation design. In 2022/2023, this laboratory has a small number of doctoral and postdoctoral places. Students and researchers who are interested in the above research are welcome to consult and contact (email: xuan.zhang@wustl.edu).
Reference materials:
1.Cao, W., Wang, C., Chen, W. et al. Fully integer grated parity–time-symmetric electronics. Nature Nanotechnology 17, 262–268 (2022). https: //doi.org /10.1038/s41565-021-01038-4
2.Liu, Y., Cao, W., Chen, W. et al. Fully integrated topological electronics. Scienti fic Reports 12, 13410 (2022). https://doi.org/ 10.1038/s41598-022-17010-8
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