Realization of multiple charge density waves in NbTe2 at the monolayer limit

Abstract

Abstract: Layered transition-metal dichalcogenides (TMDCs) down to the monolayer (ML) limit provide a fertile platform for exploring charge-density waves (CDWs). Though bulk NbTe2 is known to harbor a single axis 3*1 CDW coexisting with non-trivial quantum properties, the scenario in the ML limit is still experimentally unknown. In this study, we unveil the richness of the CDW phases in ML NbTe2, where not only the theoretically predicted 4*4 and 4*1 phases, but also two unexpected sqrt(28)*sqrt(28) and sqrt(19)*sqrt(19) phases, can be realized. For such a complex CDW system, we establish an exhaustive growth phase diagram via systematic efforts in the material synthesis and scanning tunneling microscope characterization. Moreover, we report that the energetically stable phase is the larger scale order (sqrt(19)*sqrt(19)), which is surprisingly in contradiction to the prior prediction (4*4). These findings are confirmed using two different kinetic pathways, i.e., direct growth at proper growth temperatures (T), and low-T growth followed by high-T annealing. Our results provide a comprehensive diagram of the "zoo" of CDW orders in ML 1T-NbTe2 for the first time and offer a new material platform for studying novel quantum phases in the 2D limit.

References in corpus (4)

• Dense network of one-dimensional mid-gap metallic modes in monolayer MoSe2 and their spatial undulations
• Large-gap insulating dimer ground state in monolayer IrTe2
• A novel $\sqrt{19}\times \sqrt{19}$ superstructure in epitaxially grown 1T-TaTe${}_2$
• Charge order with unusual star-of-David lattice in monolayer NbTe2

Cited by in corpus (4)

• Electronic Landscape of Group-5 Transition Metal Ditellurides $M$Te${}_2$ ($M$ = V, Nb, Ta): Multiple Crystal Phases with Local Bonds and Flat Bands
• Emergent Quantum Phenomena of Noncentrosymmetric Charge-Density Wave in 1T-Transition Metal Dichalcogenides
• The rich structural, electronic and bonding landscape of 1$T$-type TaTe${}_2$ single-layers
• Competing charge density wave phases in YNiC2