Internal Thermal Stress-Driven Phase Transformation in Van der Waals Layered Materials

Abstract

High pressure or strain is an effective strategy for generating phase transformations in van der Waals (vdW) layered materials without introducing defects, but this approach remains difficult to perform consistently. We present a scalable and facile method for achieving phase transformation in vdW materials, wherein solid vdW materials are subject to internal thermal stress within a molten metal mantle as it undergoes cooling. This internal thermal stress is principally the product of differential thermal expansion between mantle and core and can be tuned by the mantle material and temperature conditions. We validated this approach by achieving phase transformation of red phosphorus to black phosphorus, and metallic 1T′- to semiconducting 2H-MoTe2 crystals. We further demonstrate quantum electronic phase transformation of suppressed charge density wave in TiSe2 by means of electron–phonon coupling using the same system.

Observation of photoinduced polarons in semimetal 1T-TiSe2

“…Figure 1(b) presents the Raman spectrum of the mechanically exfoliated TiSe 2 crystal at room temperature, and the observed Raman peaks at 135 cm −1 and 196 cm −1 are assigned to the E g and A 1g optical phonon mode [29], respectively. In addition, according to the temperature-dependent Raman spectra presented in figure S1, the CDW transition temperature of the CVT-grown TiSe 2 is estimated to be ∼190 K [30,31]. Figure 1(c) shows the HRTEM image and the corresponding SAED pattern of the bulk TiSe 2 , indicating the single-crystalline characteristic.…”

Probing electron and lattice dynamics by ultrafast electron microscopy: Principles and applications

“…Significant progress in charge density waves (CDW) has been made in recent years in quasi‐two‐dimensional systems 117,118 . However, the correlation of charge, spin, and lattices in strongly correlated systems makes it difficult to resolve the effects of different orders on the material properties.…”

“…Significant progress in charge density waves (CDW) has been made in recent years in quasi-two-dimensional systems. 117,118 However, the correlation of charge, spin, and lattices in strongly correlated systems F I G U R E 12 Few-layer dephasing behavior of stress waves between MoS 2 layers. Reproduced with permission.…”