The group of Zhiyong Zhang and Ning Kang from the School of Electronics, Center for Carbon-based Electronics Research, and Key Laboratory of Nanodevice Physics and Chemistry, Ministry of Education, Peking University, in collaboration with the group of Yin Wang from Hongzhi Micro Technology Co., Ltd. and the group of Kaili Jiang from the Department of Physics, Tsinghua University, has made progress in the direction of quantum coherent transport research in carbon nanotubes: the first quantum interference effect with built-in electric field regulation has been achieved, and further in the low magnetic field region The AB effect of Fabry-Perot (FP) interference enhancement was observed for the first time.

On May 17, the research results were published as "Gate-Controlled Quantum Interference Effects in a Clean Single-Wall Carbon Nanotube p-n Junction", with the title "Gate-Controlled Quantum Interference Effects in a Clean Single-Wall Carbon Nanotube p-n Junction") was published online in Physical Review Letters.

As an ideal low-dimensional electronic system with unique energy band structure and high carrier mean free range, carbon nanotubes exhibit excellent quantum properties at low temperatures, showing attractive prospects for the development of high-performance integrated circuits and solid-state quantum devices.

In mesoscopic devices, achieving a deep understanding and precise regulation of quantum interference effects is not only beneficial to the study of quantum coherence phenomena in low-dimensional electronic systems, but also lays the foundation for the development of new nanoelectronic devices and quantum devices. Carbon nanotubes are tubular one-dimensional crystals composed of carbon atoms, which provide an ideal experimental platform for studying the Aharonov-Bohm (AB) effect under axial magnetic fields. However, due to their ultra-small diameters, the realization of a flux quantum in carbon tubes requires ultra-high magnetic fields (~50 T axial magnetic field for 10 nm diameter), which greatly limits the experimental observations and studies.

Early experimental studies have used multilayered carbon nanotubes with large tube diameters to reduce the magnetic field required for flux quanta, or used potential barrier tunneling to observe AB oscillations through the Schottky barrier formed at the interface between carbon nanotubes and electrodes, but all of them are difficult to overcome the difficulties such as the disorder of the system intrinsic and the fixed tunneling barrier, thus lacking stable and controllable means to study the AB effect in the one-dimensional system. 2004. Andreev theoretically proposed the possible observation of flux-modulated quantum interference effects at low fields by combining Landau-Zener tunneling with AB effects using the characteristic structure of p-n junctions (Phys. Rev. Lett. 2007, 99, 247204), but it has never been realized experimentally due to the difficulty of device tuning.

Figure 1 Double-side gate p-n junction based on a single carbon nanotube construction

Figure 2 Built-in electric field modulation with Fabry-Perot interference enhanced AB magnetoconductance oscillation

This time, the research team achieved effective modulation of the strength of single carbon nanotube p-n junctions by constructing paired side gate structures on the sheet, and obtained high-quality carbon nanotube devices operating in the ballistic transport interval (Figure 1). The characteristic non-monotonic magnetic transport behavior was successfully observed experimentally by stabilizing the device operating interval at the p-n boundary in the double-gate spectrum in the direction of the enhancement of the built-in electric field, in agreement with the theoretically predicted images (Fig. 2a-c). The AB origin of the magnetoconductivity was further confirmed by the evolutionary behavior of magnetic transport at different inclination angles at low temperatures (Fig. 2b and Fig. 2d). This non-monotonic magnetic transport behavior is experimentally observed for the first time to be greatly enhanced in the resonance region of FP (Fig. 2e), and calculations based on nonequilibrium Green's functions and density generalization further show the behavior of the transmission coefficient of resonance modulation (Fig. 2f).

This work provides a new scheme for studying quantum interference effects in the one-dimensional electronic system and developing multi-field modulation means.

Xiaosong Deng, a PhD student in the School of Electronics, Peking University, is the first author, and Ning Kang and Zhiyong Zhang are co-corresponding authors. This work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, and the Laboratory of Micro and Nano Processing Ultra-clean at Peking University.