2022 New's Items

Spectroscopy signatures of electron correlations in a trilayer graphene/hBN moiré superlattice

Yang J
Zhang Y
Chen G
Han T
Zhang Q
Zhang Y
Wang FC
Ju Lu
2022

ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. We report spectroscopy measurements of dual-gated TLG/hBN using Fourier transform infrared photocurrent spectroscopy. We observed a strong optical transition between moiré minibands that narrows continuously as a bandgap is opened by gating, indicating a reduction of the single-particle bandwidth. At half-filling of the valence flat band, a broad absorption peak emerges at ~18 milli–electron volts, indicating direct optical excitation across...

Emerging exciton physics in transition metal dichalcogenide heterobilayers

Regan EC
Wang D
Paik EY
MacDonald AH
Deng H
Wang FC
2022

Atomically thin transition metal dichalcogenides (TMDs) are 2D semiconductors with tightly bound excitons and correspondingly strong light–matter interactions. Owing to the weak van der Waals bonding between layers, TMDs can be isolated and stacked together to form synthetic heterostructures with emergent electronic and excitonic properties. In this Review, we focus on the emergent exciton physics in moiré superlattices and in TMD heterobilayers coupled to optical cavities, where exciton behaviour can be dramatically modified by the environment. In moiré superlattices, a small twist...

Correlated interlayer exciton insulator in heterostructures of monolayer WSe2 and moiré WS2/WSe2

Zhang Z
Regan EC
Wang D
Zettl A
Zaletel MP
Wang FC
2022

Moiré superlattices in van der Waals heterostructures have emerged as a powerful tool for engineering quantum phenomena. Here we report the observation of a correlated interlayer exciton insulator in a double-layer heterostructure composed of a WSe2 monolayer and a WS2/WSe2 moiré bilayer that are separated by ultrathin hexagonal boron nitride. The moiré WS2/WSe2 bilayer features a Mott insulator state when the density of holes is one per moiré lattice site...

Intralayer charge-transfer moiré excitons in van der Waals superlattices

Naik MH
Regan EC
Zhang Z
Chan YH
Wang F
Louie SG
2022

Moiré patterns of transition metal dichalcogenide heterobilayers have proved to be an ideal platform on which to host unusual correlated electronic phases, emerging magnetism and correlated exciton physics. Whereas the existence of new moiré excitonic states is established1,...

Charge Transfer Dynamics in MoSe2/hBN/WSe2 Heterostructures

Yoon Y
Zhang Z
Qi R
Joe AY
Sailus R
Watanabe K
Taniguchi T
Tongay S
Wang F
2022

Ultrafast charge transfer processes provide a facile way to create interlayer excitons in directly contacted transition metal dichalcogenide (TMD) layers. More sophisticated heterostructures composed of TMD/hBN/TMD enable new ways to control interlayer exciton properties and achieve novel exciton phenomena, such as exciton insulators and condensates, where longer lifetimes are desired. In this work, we experimentally study the charge transfer dynamics in a heterostructure composed of a 1 nm thick hBN spacer between MoSe2 and WSe2...

Big Data in a Nano World: A Review on Computational, Data-Driven Design of Nanomaterials Structures, Properties, and Synthesis

Yang RX
McCandler CA
Andriuc O
Siron M
Woods-Robinson R
Horton MK
Persson KA
2022

The recent rise of computational, data-driven research has significant potential to accelerate materials discovery. Automated workflows and materials databases are being rapidly developed, contributing to high-throughput data of bulk materials that are growing in quantity and complexity, allowing for correlation between structural–chemical features and functional properties. In contrast, computational data-driven approaches are still relatively rare for nanomaterials discovery due to the rapid scaling of computational cost for finite systems. However, the distinct behaviors at the...

Exploring the Morphotropic Phase Boundary in Epitaxial PbHf1–xTixO3 Thin Films

Acharya M
Ling H
Lou D
Ramesh M
Hanrahan B
Velarde G
Asta M
Persson KA
Martin LW
2022

Epitaxial PbHf1–xTixO3/SrTiO3(001) thin-film heterostructures are studied for a potential morphotropic phase boundary (MPB) akin to that in the PbZr1–xTixO3 system. End members, PbHfO3 and PbTiO3, were found to possess orthorhombic (Pbam) and tetragonal (P4mm) crystal structures and antiferroelectric and...

A representation-independent electronic charge density database for crystalline materials

Shen J-X
Munro JM
Horton MK
Huck P
Dwaraknath S
Persson KA
2022

In addition to being the core quantity in density-functional theory, the charge density can be used in many tertiary analyses in materials sciences from bonding to assigning charge to specific atoms. The charge density is data-rich since it contains information about all the electrons in the system. With the increasing prevalence of machine-learning tools in materials sciences, a data-rich object like the charge density can be utilized in a wide range of applications. The database presented here provides a modern and user-friendly interface for a large and continuously updated...

Materials design principles of amorphous cathode coatings for lithium-ion battery applications

Cheng J
Dong KD
Persson KA
2022

Cathode surface coatings present one of the most popular and effective solutions to suppress cathode degradation and improve cycling performance of lithium-ion batteries (LIBs). In this work, we carry out an extensive high-throughput computational study to develop materials design principles governing amorphous cathode coating selections for LIBs. Our high-throughput screening includes descriptors to evaluate the thermodynamic stability, electrochemical stability, chemical reactivity with electrolytes and cathodes, and ionic diffusion of the cathode coatings. In the ionic diffusion...