2024 New's Items

Imaging tunable Luttinger liquid systems in van der Waals heterostructures

Li H
Xiang Z
Wang T
Naik MH
Kim W
Nie J
Li S
Ge Z
He Z
Ou Y
Banerjee R
Taniguchi T
Watanabe K,
Tongay S
Zettl A
Louie SG
Zaletel MP
Crommie MF
Wang F
2024

One-dimensional (1D) interacting electrons are often described as a Luttinger liquid1,2,...

Synthesis and Polymorph Manipulation of FeSe2 Monolayers

He Z
Poudel SP
Stolz S
Wang T
Rossi A
Wang F
Mo SK
Weber-Bargioni A
Qiu ZQ
Barraza-Lopez S
Zhu T
Crommie MF
2024

Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe2 monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe2...

Wigner molecular crystals from multielectron moiré artificial atoms

Li H
Xiang Z
Reddy AP
Devakul T
Sailus R
Banerjee R
Taniguchi T
Watanabe K
Tongay S
Zettl A
Fu L
Crommie MF
Wang F
2024

Semiconductor moiré superlattices provide a versatile platform to engineer quantum solids composed of artificial atoms on moiré sites. Previous studies have mostly focused on the simplest correlated quantum solid—the Fermi-Hubbard model—in which intra-atom interactions are simplified to a single onsite repulsion energy U. Here we report the experimental observation of Wigner molecular crystals emerging from multielectron artificial atoms in twisted bilayer tungsten disulfide moiré superlattices. Using scanning tunneling microscopy, we demonstrate that Wigner molecules...

Chern Insulator States with Tunable Chern Numbers in a Graphene Moiré Superlattice

Wang S
Zhang Z
Li H
Sanborn C
Zhao W
Wang S
Watanabe K
Taniguchi T
Crommie MF
Chen G
Wang F
2024

Moiré superlattices, constituted by two-dimensional materials, demonstrate a variety of strongly correlated and topological phenomena including correlated insulators, superconductivity, and integer/fractional Chern insulators. In the realm of topological nontrivial Chern insulators within specific moiré superlattices, previous studies usually observe a single Chern number at a given filling factor in a device. Here we present the observation of gate-tunable Chern numbers within the Chern insulator state of an ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice...

Regioselective On-Surface Synthesis of [3]Triangulene Graphene Nanoribbons

Daugherty MC
Jacobse PH
Jiang J
Jornet-Somoza J
Dorit R
Wang Z
Lu J
McCurdy R
Tang W
Rubio A
Louie SG
Crommie MF
Fischer FR
2024

The integration of low-energy states into bottom-up engineered graphene nanoribbons (GNRs) is a robust strategy for realizing materials with tailored electronic band structure for nanoelectronics. Low-energy zero-modes (ZMs) can be introduced into nanographenes (NGs) by creating an imbalance between the two sublattices of graphene. This phenomenon is exemplified by the family of [n]triangulenes (nN). Here, we demonstrate the synthesis of [3]triangulene...

Synthesis and characterization of low-dimensional N-heterocyclic carbene lattices

Qie B
Wang Z
Jiang J
Zhang Z
Jacobse PH
Lu J
Li X
Liu F
Alexandrova AN
Louie SG
Crommie MF
Fischer FR
2024

The covalent interaction of N-heterocyclic carbenes (NHCs) with transition metal atoms gives rise to distinctive frontier molecular orbitals (FMOs). These emergent electronic states have spurred the widespread adoption of NHC ligands in chemical catalysis and functional materials. Although formation of carbene-metal complexes in self-assembled monolayers on surfaces has been explored, design and electronic structure characterization of extended low-dimensional NHC-metal lattices remains elusive. Here we demonstrate a modular approach to engineering one-dimensional (1D) metal-organic...

Spin disorder control of topological spin texture

Zhang H
Shao YT
Chen X
Zhang B
Wang T
Meng F
Xu K
Meisenheimer P
Chen X
Huang X
Behera P
Husain S
Zhu T
Pan H
Jia Y
Settineri N
Giles-Donovan N
He Z
Scholl A
N’Diaye A
Shafer P
Raja A
Xu C
Martin LW
Crommie MF
Yao J
Qiu Z
Majumdar A
Bellaiche L
Muller DA
Birgeneau RJ
Ramesh R
2024

Stabilization of topological spin textures in layered magnets has the potential to drive the development of advanced low-dimensional spintronics devices. However, achieving reliable and flexible manipulation of the topological spin textures beyond skyrmion in a two-dimensional magnet system remains challenging. Here, we demonstrate the introduction of magnetic iron atoms between the van der Waals gap of a layered magnet, Fe3GaTe2, to modify local anisotropic magnetic interactions. Consequently, we present direct observations of the...

Imaging moiré excited states with photocurrent tunnelling microscopy

Li H
Xiang Z
Naik MH
Kim W
Li Z
Sailus R
Banerjee R
Taniguchi T
Watanabe K
Tongay S
Zettl A
da Jornada FH
Louie SG
Crommie MF
Wang F
2024

Moiré superlattices provide a highly tuneable and versatile platform to explore novel quantum phases and exotic excited states ranging from correlated insulators to moiré excitons. Scanning tunnelling microscopy has played a key role in probing microscopic behaviours of the moiré correlated ground states at the atomic scale. However, imaging of quantum excited states in moiré heterostructures remains an outstanding challenge. Here we develop a photocurrent tunnelling microscopy technique that combines laser excitation and scanning tunnelling spectroscopy to directly visualize the electron...

Controlling structure and interfacial interaction of monolayer TaSe2 on bilayer graphene

Lee H
Im H
Choi BK
Park K
Chen Y
Ruan W
Zhong Y
Lee JE
Ryu H
Crommie MF
Shen ZX
Hwang C
Mo SK
Hwang J
2024

Tunability of interfacial effects between two-dimensional (2D) crystals is crucial not only for understanding the intrinsic properties of each system, but also for designing electronic devices based on ultra-thin heterostructures. A prerequisite of such heterostructure engineering is the availability of 2D crystals with different degrees of interfacial interactions. In this work, we report a controlled epitaxial growth of monolayer TaSe2 with different structural phases, 1H and 1 T, on a bilayer graphene (BLG) substrate using...

Manipulation of chiral interface states in a moiré quantum anomalous Hall insulator

Zhang C
Zhu T
Kahn S
Soejima T
Watanabe K
Taniguchi T
Zettl A
Wang F
Zaletel MP
Crommie MF
2024

Moiré systems made from stacked two-dimensional materials host correlated and topological states that can be electrically controlled with applied gate voltages. One prevalent form of topological state that can occur are Chern insulators that display a quantum anomalous Hall effect. Here we manipulate Chern domains in an interaction-driven quantum anomalous Hall insulator made from twisted monolayer–bilayer graphene and observe chiral interface states at the boundary between different domains. By tuning the carrier concentration, we stabilize neighbouring domains of opposite Chern...