The joint research group of Zhang Zhiyong and Kang Ning of the School of Electronics has made important progress in the study of the grid-controlled quantum interference effect of carbon nanotubes

Zhiyong Zhang and the Corning research group, together with their collaborators, have made progress in the research direction of quantum coherent transport of carbon nanotubes: the quantum interference effect regulated by the built-in electric field was realized for the first time, and the AB effect enhanced by Fabry-Perot (FP) interference was further observed in the low magnetic field region.

As an ideal low-dimensional electronic system, carbon nanotubes (CNTS) exhibit excellent quantum properties at low temperatures due to their unique band structure and high carrier mean free path, which is an attractive prospect for the development of high-performance integrated circuits and solid-state quantum devices. In mesoscopic devices, the in-depth understanding and precise regulation of quantum interference effects are not only beneficial to the study of quantum coherence in low-dimensional electronic systems, but also lay a foundation for the development of novel nanoelectronic devices and quantum devices. Carbon nanotubes are tubular one-dimensional crystals composed of carbon atoms, which provide an ideal experimental platform for the study of Aharonov-Bohm (AB) effect under axial magnetic fields. However, due to its ultra-small diameter, the realization of a magnetic fluxon in a carbon tube requires an extremely high magnetic field (about 50T axial magnetic field for a 10nm diameter), which greatly limits experimental observation and research. Early experimental studies used multilayer carbon nanotubes with large tube diameter to reduce the magnetic field required by magneto fluxons, or observed AB oscillations by using potential barrier tunneling through the Schottky barrier formed at the interface of carbon nanotubes and electrodes, but it was difficult to overcome the inherent disorder of the system and fixed tunneling barrier and other difficulties, so there was a lack of stable and controllable means to study AB effects in one-dimensional systems. In 2004, Andreev theoretically proposed that the characteristic structure of p-n junction could be used to observe the flux modulated quantum interference effect in low field by combining Landau Zener tunneling with AB effect (Phys. Rev. Lett. 2007, 99, 247204). However, it has not been realized experimentally due to the difficulty of controlling the device.

Zhang Zhiyong and Kang Ning of Peking University School of Electronics, Research Center for Carbon-based Electronics, Key Laboratory of Physics and Chemistry of NanoDevices of the Ministry of Education, in collaboration with Wang Yin team of Hongzhi Micro Technology Co., LTD., and Jiang Kaili research group of the Department of Physics of Tsinghua University, have made progress in the research direction of quantum coherent transport of carbon nanotubes: The quantum interference effect regulated by the built-in electric field is realized for the first time, and the AB effect enhanced by Fabry-Perot (FP) interference is further observed in the low magnetic field region. By constructing a paired side-gate structure on the wafer, the research team achieved effective regulation of the p-n junction strength of a single carbon nanotube, and obtained high-quality carbon nanotube devices operating in the ballistic transport interval (Figure 1). By stabilizing the device's operating interval at the p-n boundary in the two-gate spectrum, the characteristic non-monotone magnetic transmission behavior along the direction of the built-in electric field enhancement is successfully observed in the experiment, which is consistent with the image predicted by the theory (Figure 2a-c). The AB origin of the permeability is further confirmed by the evolutionary behavior of magnetic transport at different inclination angles at low temperatures (Figures 2b and 2d). For the first time, this non-monotone magnetic transmission operation is observed to be greatly enhanced in the resonance region of FP (Figure 2e), and the calculation method based on non-equilibrium Green's function and density functional further shows the transmission coefficient behavior of resonance modulation (Figure 2f). This work provides a new scheme for studying quantum interference effects and developing multi-field control methods in one-dimensional electronic systems.

FIG. 1 Two-sided gate p-n junction based on a single carbon nanotube

FIG. 2 AB permeability oscillations enhanced by built-in electric field modulation with Fabry-Perot interference

Related research results are published in the "Gate-Controlled Quantum Interference Effects in a Clean Single-Wall Carbon Nanotube p-n junction. "Junction" was published online May 17 in the journal Physical Review Letters. Deng Xiaosong, a doctoral candidate at Peking University's School of Electronics, is the first author, and Kang Ning and Zhang Zhiyong are co-corresponding authors. This work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, and the Micro-Nano Processing Ultra-Clean Laboratory of Peking University.

Key words:

effect     quantum     carbon nanotube     study     Intervene    ab     device     realize