Visualizing the Anomalous Charge Density Wave States in Graphene/NbSe<sub>2</sub> Heterostructures.
basic_science · Level V
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- Record sourced from PubMed, PMID 33002238.
- Also identified by DOI 10.1002/adma.202003746.
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Abstract
Metallic layered transition metal dichalcogenides (TMDs) host collective many-body interactions, including the competing superconducting and charge density wave (CDW) states. Graphene is widely employed as a heteroepitaxial substrate for the growth of TMD layers and as an ohmic contact, where the graphene/TMD heterostructure is naturally formed. The presence of graphene can unpredictably influence the CDW order in 2D CDW conductors. This work reports the CDW transitions of 2H-NbSe<sub>2</sub> layers in graphene/NbSe<sub>2</sub> heterostructures. The evolution of Raman spectra demonstrates that the CDW phase transition temperatures (T<sub>CDW</sub> ) of NbSe<sub>2</sub> are dramatically decreased when capped by graphene. The induced anomalous short-range CDW state is confirmed by scanning tunneling microscopy measurements. The findings propose a new criterion to determine the T<sub>CDW</sub> through monitoring the line shape of the A<sub>1g</sub> mode. Meanwhile, the 2D band is also discovered as an indicator to observe the CDW transitions. First-principles calculations imply that interfacial electron doping suppresses the CDW states by impeding the lattice distortion of 2H-NbSe<sub>2</sub> . The extraordinary random CDW lattice suggests deep insight into the formation mechanism of many collective electronic states and possesses great potential in modulating multifunctional devices.