Raman spectrum of layered jacutingaite (Pt₂HgSe₃) crystals—Experimental and theoretical study

Abstract

Jacutingaite (Pt2HgSe3) is a recently discovered layered platinum‐group mineral. Recent experimental studies have shown that it displays the properties of a quantum spin Hall insulator (QSHI), and theoretical studies indicate that its two‐dimensional monolayer is a QSHI with a robust topological gap of ∼0.5 eV. Jacutingaite is thus promising for potential applications to nanoelectronics and spintronics. The Raman spectrum of three‐dimensional bulk jacutingaite and the symmetries of its vibrational modes, fundamental for understanding structural modifications of this material, are still unexplored. Here, we address the zone‐center Raman optical phonons of bulk jacutingaite by experiments, symmetry, and first‐principles calculations. The improved synthesis used here provided crystals of higher purity and of micrometer size, allowing the study of single crystals. Polarized Raman spectroscopy was used to assign the symmetries of nine out of the 11 Raman‐active modes expected by group theory and their respective selection rules. The calculated wavenumbers of the Raman‐active modes, in addition to their atomic displacements, are in very good agreement with experiments. In addition, we discuss the use of different exchange correlation functionals within density functional theory, as local functionals and nonlocal functionals that best describe van der Waals interactions. The influence of the inclusion of spin–orbit coupling on calculated vibrational phonon wavenumbers and lattice parameters is commented, and it was found that the local density approximation provides a good description. Our results are of paramount importance to further exploitation of the effects of jacutingaite's structural modifications to tune its properties, as well as for its structural, optical, electronic, mechanical, and thermal applications.

Raman and Far-Infrared Synchrotron Nanospectroscopy of Layered Crystalline Talc: Vibrational Properties, Interlayer Coupling, and Symmetry Crossover

“…The low-frequency rigid-layer modes in LMs can be rationalized by the application of a linear-chain model. 8,[74][75][76][77][78]80,81 By fitting the linear-chain model to our calculation results (red line in Figure 8), we can obtain the interlayer force constants of layered talc, from bulk to the 2L regime. We find that the interlayer force constant for shear movement (K LSM ) along the armchair-and zigzag-like directions are 0.44 × 10 19 and 4.14 × 10 19 N m −3 , respectively.…”

“…The low-frequency rigid-layer modes in LMs can be rationalized by the application of a linear-chain model 8,[77][78][79][80][81]83,84 . By fitting the linear-chain model to our calculation results (red line in Figure 8), we can obtain the interlayer force constants of layered talc, from bulk to the 2L regime.…”

Phyllosilicates as earth-abundant layered materials for electronics and optoelectronics: Prospects and challenges in their ultrathin limit

“…Note that by performing such IR and Raman measurements, besides their vibrational features, one can collect the low-frequency modes (<100 cm -1 ) for estimation of the interlayer interactions and related mechanical properties of these LMs. 26,138,139 In addition to the aforementioned vibrational spectroscopies, Brillouin spectroscopy could be another useful technique to access the force constants between adjacent lamellas in phyllosilicates. This would also unveil their low-frequency rigid-layer modes.…”

Exploring the structural and optoelectronic properties of natural insulating phlogopite in van der Waals heterostructures

“…Layered materials (LMs) [1], for which graphene is the prime example, have obtained vast attention in the last years. So far, more than 1800 LMs have been computationally identified [2][3][4], while many of them have been naturally obtained or synthesized [5][6][7][8][9][10][11][12][13]. Thus, as soon as a new LM is identified, the investigation of its optical, mechanical and electrical properties is promptly examined [14].…”