Raman anomalies as signatures of pressure induced electronic topological and structural transitions in black phosphorus: Experiments and theory

Abstract

We report high pressure Raman experiments of Black phosphorus (BP) up to 24 GPa. The line widths of first order Raman modes A 1 g , B2g and A 2 g of the orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density functional analysis reveals that this is associated with the anomalies in electron-phonon coupling at the semiconductor to topological insulator transition through inversion of valence and conduction bands marking a change from trivial to nontrivial electronic topology. The frequencies of B2g and A 2 g modes become anomalous in the rhombohedral phase at 7.4 GPa, and new modes appearing in the rhombohedral phase show anomalous softening with pressure. This is shown to originate from unusual structural evolution of black phosphorous with pressure, based on first-principles theoretical analysis.

High pressure anomalies in exfoliated MoSe2: resonance Raman and x-ray diffraction studies

“…However at this moment it is difficult to confirm it without any detailed theoretical study. Similar anomalies have been observed earlier during ETT in other systems [36,39,40,42,43,45,46] and are probably a precursor to semiconductor to metallic transition. It may be noted that the triclinic phase, which is known to be metallic also shows a slope change in Eulerian strain at 17GPa, which matches well with the end of plateau region in c/a-ratio of the hexagonal phase.…”

“…We clearly see the electron phonon coupling changes with pressure, showing a broad minimum reflecting similar behaviour of FWHM. Similar dip in electron phonon coupling was observed in Black Phosphorus and attributed to ETT [46]. Pressure dependent resistivity measurements by Zhao et al [11] show a step like characteristic in the pressure range about 12-20 GPa similar to the c/a-ratio of the hexagonal phase.…”

2D Materials and Heterostructures at Extreme Pressure

“…The pressure-induced electronic topological and structural transitions have been investigated for black phosphorus experimentally and theoretically. [33] The accurate HSE calculations demonstrated the occurrence of band inversion at 1.2 GPa. The strong topological index 0 = 0 for P < 1.2 GPa and 0 = 1 for P ≥ 1.2 GPa are observed, confirming the transition of the topological insulator phase at above 1.2 GPa.…”

“…The strong topological index 0 = 0 for P < 1.2 GPa and 0 = 1 for P ≥ 1.2 GPa are observed, confirming the transition of the topological insulator phase at above 1.2 GPa. [33] Furthermore, the crystal structures' evolutions of phosphorus are demonstrated under different pressures ( Figure 4g). [32] Under ambient pressure, red phosphorus was stable with triclinic structure (P-I), whereas BP (Cmca) nearly degenerated.…”

“…[11][12][13] Pressure, being an important thermodynamic variable, could provide a powerful method to tune the atomic, electronic, and crystal structures of 2D materials without introducing damages and impurities. [14][15][16] As an example, the pressure-induced dramatic changes in electronic structures and structural phase transitions of transition metal dichalcogenides (TMDs), [17][18][19][20] boron nitride (BN), [21][22][23][24][25][26] MXene, [27][28][29] and black phosphorene (BP) [30][31][32][33][34] have been reported. [15,[17][18][19][20][35][36][37] Compared with their bulk counterparts, 2D TMDs exhibit thickness-dependent phase transitions (from 2H c to 2H a ) under high pressure, and thinner films are more sensitive to pressure in terms of Raman vibration modes.…”