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Scientific article
Open access
English

Holographic imaging of the complex charge density wave order parameter

Published inPhysical Review Research, vol. 1, no. 3, 033114
Publication date2019
Abstract

The charge density wave (CDW) in solids is a collective ground state combining lattice distortions and charge ordering. It is defined by a complex order parameter with an amplitude and a phase. The amplitude and wavelength of the charge modulation are readily accessible to experiment. However, accurate measurements of the corresponding phase are significantly more challenging. Here we combine reciprocal and real space information to map the full complex order parameter based on topographic scanning tunneling microscopy (STM) images. Our technique overcomes limitations of Fourier space based techniques to achieve distinct amplitude and phase images with high spatial resolution. Applying this analysis to transition metal dichalcogenides provides striking evidence that their CDWs consist of three individual unidirectional charge modulations whose ordering vectors are connected by the fundamental rotational symmetry of the crystalline lattice. Spatial variations in the relative phases of these three modulations account for the different CDW contrasts often observed in STM topographic images. Phase images further reveal topological defects and discommensurations, a singularity predicted by theory for a nearly commensurate CDW. Such precise real space mapping of the complex order parameter provides a powerful tool for a deeper understanding of the CDW ground state whose formation mechanisms remain largely unclear.

Keywords
  • Charge density wave
  • Scanning tunneling microscopy
  • Transition metal dichalcogenide
Research group
Funding
  • Swiss National Science Foundation - 182652
  • Swiss National Science Foundation - 147607
Citation (ISO format)
PASZTOR, Arpad et al. Holographic imaging of the complex charge density wave order parameter. In: Physical Review Research, 2019, vol. 1, n° 3, p. 033114. doi: 10.1103/PhysRevResearch.1.033114
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Article (Published version)
Identifiers
ISSN of the journal2643-1564
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Technical informations

Creation11/19/2019 8:52:00 PM
First validation11/19/2019 8:52:00 PM
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