arXiv subjects

Lu Lyu

Publications and source records attributed to Lu Lyu.

4 recordsLinked to original sources

arXiv2023

Temperature-driven confinements of surface electrons and adatoms in a weakly interacting 2D organic porous network

Two-dimensional organic porous networks (2DOPNs) have opened new vistas for tailoring the physicochemical characteristics of metallic surfaces. These typically chemically bound nanoporous structures act as periodical quantum wells leading to the 2D confinements of surface electron gases, adatoms and molecular guests. Here we propose a new type of porous network with weakly interacting 2,4,6-triphenyl-1,3,5-triazine (TPT) molecules on a Cu(111) surface, in which a temperature-driven (T-driven) phase transition can reversibly alter the supramolecular structures from a close-packed (CP-TPT) phase to a porous-network (PN-TPT) phase. Crucially, only the low-temperature PN-TPT exhibits subnano-scale cavities that can confine the surface state electrons and metal adatoms. The confined surface electrons undergo a significant electronic band renormalization. To activate the spin degree of freedom, the T-driven PN-TPT structure can additionally trap Co atoms within the cavities, forming highly ordered quantum dots. Our theoretical simulation reveals a complex spin carrier transfer from the confined Co cluster to the neighbouring TPT molecules via the underlying substrate. Our results demonstrate that weakly interacting 2DOPN offers a unique quantum switch capable of steering and controlling electrons and spin at surfaces via tailored quantum confinements.

cond-mat.mtrl-sci↗

arXiv2023

Exploring the third dimension in quantum confinement of surface electrons

Quantum confinement of surface electrons in two-dimensional metal-organic porous networks offers a powerful route to engineer electronic states for emerging quantum and spintronic technologies at the molecular scale. To date, such confinement has been understood primarily in terms of lateral, two-dimensional surface potential landscapes. Here, we demonstrate the pivotal role of vertical variations in the surface potential on the quantum confinement of surface electrons. We investigate the confinement behavior of both Shockley surface state and image potential state electrons with their distinct vertical electron density distributions in an exemplary Cu-T4PT metal-organic porous network on Cu(111). Advanced spectroscopic techniques reveal a substantial band renormalization for the image state electrons, manifested as a significant increase in their effective mass, whereas the Shockley state electrons remain almost unchanged. Such striking divergence is attributed to the distinct three-dimensional potential landscape of the Cu-T4PT network with a strong repulsive potential at the vertical position of the molecular backbone and leaky channels underneath the Cu coordination spheres. Our findings demonstrate the essential role of vertical potential engineering in designing quantum confined states and thus advance the control of electronic properties and quantum phenomena on the nanoscale.

cond-mat.mtrl-sci↗

arXiv2023

Tailoring the ferromagnetic surface potential landscape by a templating two-dimensional metal-organic porous network

Two-dimensional metal-organic porous networks (2D-MOPNs) have been identified as versatile nanoarchitectures to tailor surface electronic and magnetic properties on noble metals. In this context, we propose a protocol to redecorate a ferromagnetic surface potential landscape using a 2D-MOPN. Ultrathin cobalt (Co) films grown on Au(111) exhibit a well-ordered surface triangular reconstruction. On the ferromagnetic surface, the adsorbed 2,4,6-tris(4-pyridyl)-1,3,5triazine (T4PT) molecules can coordinate with the native Co atoms to form a large-scale Co-T4PT porous network. The Co-T4PT network with periodic nanocavities serves as a templating layer to reshape the ferromagnetic surface potential. The subsequently deposited C60 molecules are steered by the network porous potential and the neighboring C60 interactions. The prototype of the ferromagnetic-supported 2D-MOPN is a promising template for the tailoring of molecular electronic and spin properties.

cond-mat.mtrl-sci↗

arXiv2021

Atomic and mesoscopic structure of Dy-based surface alloys on noble metals

Surface alloys are a highly tunable class of low dimensional materials with the opportunity to tune and control the spin and charge carrier functionalities on the nanoscale. Here, we focus on the atomic and mesoscopic structural details of three distinctive binary rare-earth-noble metals (RE/NM) surface alloys by employing scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Using Dysprosium as the guest element on fcc(111) noble metal substrates, we identify the formation of non-commensurate surface alloy superstructures which exhibit homogeneous moir\'e patterns for DyCu2/Cu (111) and DyAu2/Au(111), while an inhomogeneous one is found for DyAg2/Ag(111). The variations in the local structure are analyzed for all three surface alloys and the observed differences are discussed in the light of the lattice mismatches of the alloy layer with respect to the underlying substrate. For the particularly intriguing case of a Dy-Ag surface alloy, the surface alloy layer does not show a uniform long-range periodic structure, but consists of local hexagonal tiles separated by extended domain walls. These domain walls exist to relief the in-plane strain within the DyAg2 surface alloy layer. Our findings clearly demonstrate that surface alloying is an intriguing tool to tailor both the local atomic, but also the mesoscopic moir\'e structures of metallic heterostructures.

cond-mat.mtrl-sci↗