Charge density wave and atomic trimerization in layered transition-metal dichalcogenides 1T-MX₂materials

Abstract

In this work, structural investigation and physical measurements of layered transitionmetal dichalcogenides (TMDs) 1T -MX2 materials revealed a series of remarkable phenomena in correlation with structural transitions. Our results show that notable structural transformations, such as charge density wave (CDW) transitions, atomic ordering, and micro-twinning could be introduced via chemical substitution in 1T -MX2. It was demonstrated that substitution of S by Se in 1T -TaS2−xSex resulted in clear changes in the incommensurability of the CDW state; substitution of Se by Te could destruct the CDW state and yield atomic ordering with visible trimerization of the metallic ions. Furthermore, these structural changes yielded a monoclinic stacking along the c-axis direction. Additionally, on substitution of the metal atoms in 1T -MX2, e.g., 1T -NbTe2, structural distortion in the a-b plane could clearly be observed, and highdensity twinning lamella often appeared in the crystals because of enhanced intralayer structural deformation. These phase transitions and their relevant structural features could primarily be corelated with alteration of the superconductivity and other physical properties.

Niobium tellurium as a novel broadband saturable absorber for pulsed fiber lasers

“…The vibration peak at 113 cm −1 conforms to the in-plane E g vibration mode, and the vibration peak at 133 cm −1 exhibits the out-of-plane A 1g vibration mode, which is attributed to the typical NbTe 2 structure. These peaks are highly consistent with previous reports 38,44 (WITec, Alpha300RAS). The morphology of the NbTe 2 nanosheets was characterized by high-resolution transmission electron microscopy (Talos F200X G2).…”

“…[38][39][40] Besides, as an important member of metallic transition metal dichalcogenides (MTMDCs), MTe 2 (M = V, Nb, Ta) has been regarded as a potential platform for the research of fundamental physical phenomena, due to its unique physical properties. [41][42][43][44] Nevertheless, the nonlinear photonics of the MTe 2 (M = V, Nb, Ta) are still not getting enough attention, nor is there any experimental research on ultrafast optical applications to date. NbTe 2 , a typical kind of VB group layered MTMDC, has been demonstrated as having such advantages as CDW, strong electron coupling, SC, electrocatalytic activity, the quantum spin Hall effect, and so on.…”

Ultrafast optical melting of trimer superstructure in layered 1T'-TaTe2

“…1, with a q vector of 1/3 (111). Such peaks have been observed in prior TEM studies of TaTe 2 59,60 . They are not predicted to appear in kinematical simulations: instead, their presence has been attributed…”

“…The pattern at 10 K in Fig. 1b reveals the appearance of new satellite peaks surrounding the main lattice peaks as a result of the emergent (3 × 3) periodic lattice distortion (PLD), in concordance with Ta trimer cluster formation and the associated unit cell tripling 33,[36][37][38] .…”

“…The room temperature distorted monoclinic 1T' crystal structure is characterised by an intra-layer (3 × 1) linear stripe-like order composed of double zigzag Ta trimer chains. A structural transition into a phase with (3 × 3) order occurs at a temperature of 170 K, with Ta atoms forming trimer clusters along the linear chains with commensurate CDW-like order 33,[36][37][38] . Unlike other TaX 2 CDW systems 39,40 , the low temperature phase ordering of TaTe 2 exhibits metallic behaviour, with enhanced conductivity and magnetic susceptibility 41 .…”