Charge Density Wave Transition in (PbSe)_1+δ(VSe₂)_n Compounds with n = 1, 2, and 3

Abstract

A series of (PbSe)1+δ(VSe2) n heterostructures with extensive turbostratic disorder were synthesized with n = 1–3 through low temperature annealing of appropriately designed layered precursors. The crystal structures consist of alternating layers of CdI2 type structured VSe2 and distorted NaCl type structured PbSe. The n = 1 compound has a positive Hall coefficient and a charge density wave like transition at 100 K, during which the resistivity increases by a factor of 3.5 and the Hall coefficient increases by a factor of 8. The n = 2 and 3 compounds have negative Hall coefficients and significantly smaller changes in the slope of the resistivity and Hall coefficient as a function of temperature at similar temperatures. The distinctly different transport properties of the compound containing a monolayer of VSe2 compared to compounds with thicker VSe2 layers highlights the complexity of the electronic structure of these stacked systems. The differences cannot be simply explained by charge transfer between VSe2 and PbSe within a rigid band model. More sophisticated interactions between the constituent layers, electron–phonon interactions, and/or correlation between electrons need to be considered to explain the change in carrier type and the charge density wave (CDW) transition.

Pseudogap, Fermi arc, and Peierls-insulating phase induced by 3D–2D crossover in monolayer VSe2

“…Perhaps the present result is the first realization of an atomic-layer Peierls insulator driven by the 3D-2D crossover. The present discovery of Peierls insulating ground state in monolayer VSe2 supports the recent report that bulk 1T-VSe2 becomes to show an insulating behavior below TCDW in transport measurement when a SnSe/PbSe layer is inserted (intercalated) between adjacent VSe2 monolayers [25,26].…”

Strong Non‐Epitaxial Interactions: Crystallographically Aligned PbSe on VSe2

“…Since only 00 l reflections are observed, it is crystallographically aligned to the substrate. The c ‐axis lattice parameter determined from the 00 l reflections (12.28(1) Å) is close to the previously reported value for [(PbSe) 1.11 ] 1 (VSe 2 ) 1 ,12.25(1) Å . The in‐plane diffraction pattern of the as deposited sample (Figure b) contains broad reflections of both PbSe and VSe 2 , further indicating that [(PbSe) 1.11 ] 1 (VSe 2 ) 1 forms during the deposition.…”

Dynamic instabilities in strongly correlated VSe2 monolayers and bilayers

“…Polytype NM AFM NM AFM 1 AFM 2 AFM 3 AFM 4 1T 97 25 94 2 25 24 25 2H 157 106 148 -1 102 102 - larger than in the bulk. [48][49][50][51][52][53][54][55][56]83 The magnetization increases significantly from 0.6 -0.7 µ B to slightly above unity. This is mostly due to the strong increase of the magnetic moment of the V atom, which almost doubles.…”

“…This change in the band structure is consistent with electronic transport properties in ferecrystals and in bulk VSe 2 where a sharp increase in the Hall coefficient was observed and attributed to a reduction in carrier concentration without becoming insulating. 40,48,49,52,56,83,96 The periodic structural distortions along with the opening of band gaps indicate a Peierls-type transition at low temperatures. Comparing the magnetic properties with experimental data is challenging.…”

“…The compounds [(MSe) 1+δ ] m [VSe 2 ] 1 (M = Pb, Sn) have a relatively constant a-axis lattice parameter of a = 3.42Å, regardless of m, the thickness of the MSe layer. [52][53][54][55][56]83 The in-plane lattice parameter a of the isolated VSe 2 monolayers calculated with different functionals are shown in Figure 2c. For all functionals, the a-axis lattice parameter increases with increasing U eff .…”