Quantum interference has been intensively pursued in molecular electronics to investigate and utilize coherent electron transport at the ultra-small level. An essential type of quantum interference with drastic destructive-constructive switching, known as Fano interference, has been widely reported in various kinds of nanoelectronics electronic systems, but not yet been electrostatically gating in a single-molecule device. Here, we fabricate the three-terminal single-molecule transistors based on the molecule with a long backbone and a side group to demonstrate the gate-controllable Fano interference. By applying bias and gate voltages, the two-dimensional differential conductance map shows the noncentrosymmetrical Fano patterns. Combined with the electron transport model and the first principles calculations, the resonant parameters of the Fano interference can unveil the coupling geometry of the junction and the spatial distribution of the resonant states. Our findings provide an instrumental method to induce and utilize the quantum interference behaviours at the molecular level.
Jinghao Deng#, Deping Guo#, Yao Wen, Shuangzan Lu, Zhengbo Cheng, Zemin Pan, Tao Jian, Yusong Bai, Hui Zhang, Wei Ji*, Jun He*, Chendong Zhang*
Abstract:
Multiferroicity allows magnetism to be controlled using electric fields or vice versa, which has gained tremendous interest in both fundamental research and device applications. A reduced dimensionality of multiferroic materials is highly desired for device miniaturization, but the coexistence of ferroelectricity and magnetism at the two-dimensional limit is still debated. Here, we used a NbSe2 substrate to break both the C3 rotational and inversion symmetries in monolayer VCl3 and thus introduced exceptional in-plane ferroelectricity into a two dimensional magnet. Scanning tunnelling spectroscopy directly visualized ferroelectric domains and manipulated their domain boundaries in monolayer VCl3, where coexisting antiferromagnetic order with canted magnetic moments was verified by vibrating sample magnetometer measurements. Our density functional theory calculations highlight the crucial role that highly directional interfacial Cl–Se interactions play in breaking the symmetries and thus in introducing in-plane ferroelectricity, which was further verified by examining an ML-VCl3/graphene sample. Our work demonstrates an approach to manipulate the ferroelectric states in monolayered magnets through van der Waals interfacial interactions.
Fig. 1. Morphology and atomic structure of ML-VCl3 on a NbSe2 substrate.
Fig. 2. IP electric polarizations characterized by band bending near DWs.
Fig. 3. Experimental and theoretical investigations of the magnetic order in epitaxy ML-VCl3.
Fig. 4. Anisotropic charge transfer–induced IP ferroelectricity and comparison with the VCl3-graphene interface.
Altermagnetism has recently attracted significant interest in three- and two-dimensional materials, yet its realization in quasi-one-dimensional (Q1D) materials remains largely unexplored due to stringent symmetry constraints. Here, we systematically investigated the emergence of altermagnetism in 30 Q1D monolayer prototypes, self-assembled from intra-chain anti-ferrimagnetically coupled XYn single-atomic magnetic chains, using symmetry analysis and high-throughput density functional theory calculations. Symmetry analysis identifies four structural prototypes capable of hosting altermagnetism, which expand to 192 monolayers upon materialization. Our calculations further reveal eight dynamically stable Q1D altermagnets, all belonging the AA-stacked intra-chain AFM coupled β-XY₃ prototype, exhibiting d-wave-like spin splitting. Furthermore, we demonstrate the tunability of altermagnetic properties by varying inter-chain spacing and applying external electric fields. By optimizing these parameters, altermagnetism can be significantly enhanced, with spin splitting reaching several hundred meV in CoTe3, or substantially suppressed, leading to a transition to a nodal-line semiconducting state in CrCl3. These findings establish a diverse and highly tunable family of Q1D altermagnetic candidate materials.
The structure and dynamics of ferroelectric domain walls are essential for polarization switching in ferroelectrics, which remains relatively unexplored in two-dimensional ferroelectric α-In2Se3. Interlayer interactions engineering via selecting the stacking order in two-dimensional materials allows modulation of ferroelectric properties. Here, we report stacking-dependent ferroelectric domain walls in 2H and 3R stacked α-In2Se3, elucidating the resistance switching mechanism in ferroelectric semiconductor-metal junction devices. In 3R α-In2Se3, the in-plane movement of out-of-plane ferroelectric domain walls yield a large hysteresis window. Conversely, 2H α-In2Se3 devices favor in-plane domain walls and out-of-plane domain wall motion, producing a small hysteresis window. High electric fields induce a ferro-paraelectric phase transition of In2Se3, where 3R In2Se3 reaches the transition through intralayer atomic gliding, while 2H In2Se3 undergoes a complex process comprising intralayer bond dissociation and interlayer bond reconstruction. Our findings demonstrate tunable ferroelectric properties via stacking configurations, offering an expanded dimension for material engineering in ferroelectric devices.
Deping Guo (郭的坪)#, Cong Wang (王聪)#, Lvjin Wang (王侣锦), Yunhao Lu (陆赟豪), Hua Wu (吴骅), Yanning Zhang (张妍宁), and Wei Ji (季威)*
Abstract:
Two-dimensional (2D) van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit, indicating a considerable potential to advance spintronic applications. Theoretical predictions thus far have not ascertained whether monolayer VCl3 is a ferromagnetic (FM) or anti-FM monolayer; this also remains to be experimentally verified. We theoretically investigate the influence of potential factors, including 𝐶3 symmetry breaking, orbital ordering, epitaxial strain, and charge doping, on the magnetic ground state. Utilizing first-principles calculations, we predict a collinear type-III FM ground state in monolayer VCl3 with a broken 𝐶3 symmetry, wherein only the former two of three 𝑡2g orbitals (𝑎1g, 𝑒 𝜋 g2 and 𝑒 𝜋 g1) are occupied. The atomic layer thickness and bond angles of monolayer VCl3 undergo abrupt changes driven by an orbital ordering switch, resulting in concomitant structural and magnetic phase transitions. Introducing doping to the underlying Cl atoms of monolayer VCl3 without 𝐶3 symmetry simultaneously induces in- and out-of-plane polarizations. This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain. The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl3.
