Triggering a global density wave instability in graphene via local symmetry-breaking
Authors:
Amy C. Qu,
Pascal Nigge,
Stefan Link,
Giorgio Levy,
Matteo Michiardi,
Parsa L. Spandar,
Tiffany Matthé,
Michael Schneider,
Sergey Zhdanovich,
Ulrich Starke,
Christopher Gutiérrez,
Andrea Damascelli
Abstract:
Two-dimensional quantum materials offer a robust platform for investigating the emergence of symmetry-broken ordered phases owing to the high tuneability of their electronic properties. For instance, the ability to create new electronic band structures in graphene through moiré superlattices from stacked and twisted structures has led to the discovery of several correlated and topological phases.…
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Two-dimensional quantum materials offer a robust platform for investigating the emergence of symmetry-broken ordered phases owing to the high tuneability of their electronic properties. For instance, the ability to create new electronic band structures in graphene through moiré superlattices from stacked and twisted structures has led to the discovery of several correlated and topological phases. Here we report an alternative method to induce an incipient symmetry-broken phase in graphene at the millimetre scale. We show that an extremely dilute concentration ($<\!0.3\% $) of surface adatoms can self-assemble and trigger the collapse of the graphene atomic lattice into a distinct Kekulé bond density wave phase, whereby the carbon C-C bond symmetry is broken globally. Using complementary momentum-resolved techniques such as angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED), we directly probe the presence of this density wave phase and confirm the opening of an energy gap at the Dirac point. We further show that this Kekulé density wave phase occurs for various Fermi surface sizes and shapes, suggesting that this lattice instability is driven by strong electron-lattice interactions. Our results demonstrate that dilute concentrations of self-assembled adsorbed atoms offer an attractive alternative route towards designing novel quantum phases in two-dimensional materials.
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Submitted 23 April, 2022;
originally announced April 2022.
Room temperature strain-induced Landau levels in graphene on a wafer-scale platform
Authors:
P. Nigge,
A. C. Qu,
É. Lantagne-Hurtubise,
E. Mårsell,
S. Link,
G. Tom,
M. Zonno,
M. Michiardi,
M. Schneider,
S. Zhdanovich,
G. Levy,
U. Starke,
C. Gutiérrez,
D. Bonn,
S. A. Burke,
M. Franz,
A. Damascelli
Abstract:
Graphene is a powerful playground for studying a plethora of quantum phenomena. One of the remarkable properties of graphene arises when it is strained in particular geometries and the electrons behave as if they were under the influence of a magnetic field. Previously, these strain-induced pseudomagnetic fields have been explored on the nano- and micrometer-scale using scanning probe and transpor…
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Graphene is a powerful playground for studying a plethora of quantum phenomena. One of the remarkable properties of graphene arises when it is strained in particular geometries and the electrons behave as if they were under the influence of a magnetic field. Previously, these strain-induced pseudomagnetic fields have been explored on the nano- and micrometer-scale using scanning probe and transport measurements. Heteroepitaxial strain, in contrast, is a wafer-scale engineering method. Here, we show that pseudomagnetic fields can be generated in graphene through wafer-scale epitaxial growth. Shallow triangular nanoprisms in the SiC substrate generate strain-induced uniform fields of 41 T. This enables the observation of strain-induced Landau levels at room temperature, as detected by angle-resolved photoemission spectroscopy, and confirmed by model calculations and scanning tunneling microscopy measurements. Our work demonstrates the feasibility of exploiting strain-induced quantum phases in two-dimensional Dirac materials on a wafer-scale platform, opening the field to new applications.
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Submitted 22 November, 2019; v1 submitted 1 February, 2019;
originally announced February 2019.