Recent progresses of quantum confinement in graphene quantum dots

Abstract

Graphene quantum dots (GQDs) not only have potential applications on spin qubit, but also serve as essential platforms to study the fundamental properties of Dirac fermions, such as Klein tunneling and Berry phase. By now, the study of quantum confinement in GQDs still attract much attention in condensed matter physics. In this article, we review the experimental progresses on quantum confinement in GQDs mainly by using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Here, the GQDs are divided into Klein GQDs, bound-state GQDs and edge-terminated GQDs according to their different confinement strength. Based on the realization of quasi-bound states in Klein GQDs, external perpendicular magnetic field is utilized as a manipulation approach to trigger and control the novel properties by tuning Berry phase and electron-electron (e-e) interaction. The tip-induced edge-free GQDs can serve as an intuitive mean to explore the broken symmetry states at nanoscale and single-electron accuracy, which are expected to be used in studying physical properties of different two-dimensional materials. Moreover, high-spin magnetic ground states are successfully introduced in edge-terminated GQDs by designing and synthesizing triangulene zigzag nanographenes.

Stepwise reduction of a corannulene-based helical molecular nanographene with Na metal

“…Among the different procedures to open a bandgap for electronic applications, 7 quantum confinement of the electrons in small flakes of graphene, 8 the so-called nanographenes (NGs) 9 or graphene quantum dots (GQD), 10 has been extensively used. The controlled bottom-up preparation of monodisperse molecular NGs by organic chemistry protocols, offers new synthetic opportunities for PAHs as starting building blocks.…”

An Overview on Carbon Quantum Dots Optical and Chemical Features

“…The HOMO–LUMO gap increases when the CD size decreases, leading to the emission of photons in the UV region with an improvement in the quantum yield (QY) [ 64 ]. The fluorescence emission for CDs with π-domains of larger size (i.e., GQDs, CQNDs) is mainly due to conjugated π-electrons of the aromatic carbon domains [ 65 ]. Larger π-domains reduced the HOMO–LUMO gap and red shifted the fluorescence emission peak [ 62 ].…”

Gate‐Controlled Quantum Dots Based on 2D Materials

“…For example, gatetunable quantum confinement has been achieved using quantum Hall gap [164] or local strain [195] . Also, edge-free graphene quantum dots can be induced by the tip of a scanning tunneling microscope [196][197][198] .…”

“…[195] Also, edge-free graphene quantum dots can be induced by the tip of a scanning tunneling microscope. [196][197][198]…”