Lattice dynamics and elastic properties of black phosphorus

Pogna, Eva A. A.; Bosak, Alexeï; Chumakova, A. V.; Milman, Victor; Winkler, Björn; Viti, Leonardo; Vitiello, Miriam S.

doi:10.1103/physrevb.105.184306

Cited by 11 publications

(6 citation statements)

References 74 publications

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“…The dynamical matrices were calculated on an 8 × 8 × 8q-point grid, and the phonon dispersions and density of states were obtained by Fourier interpolation. 34 is in agreement with a recent X-ray experimental study 48 . b Angle dependence of the phonon wave-vectors with a frequency of 20 cm −1 projected in the xz plane.…”

Section: Calculationssupporting

confidence: 92%

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The phonon thermal Hall angle in black phosphorus

Machida

Subedi

et al. 2023

Nat Commun

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The origin of phonon thermal Hall Effect (THE) observed in a variety of insulators is yet to be identified. Here, we report on the observation of a thermal Hall conductivity in a non-magnetic elemental insulator, with an amplitude exceeding what has been previously observed. In black phosphorus (BP), the longitudinal (κii), and the transverse, κij, thermal conductivities peak at the same temperature and at this peak temperature, the κij/κjj/B is ≈ 10−4−10−3 T−1. Both these features are shared by other insulators displaying THE, despite an absolute amplitude spreading over three orders of magnitude. The absence of correlation between the thermal Hall angle and the phonon mean-free-path imposes a severe constraint for theoretical scenarios of THE. We show that in BP a longitudinal and a transverse acoustic phonon mode anti-cross, facilitating wave-like transport across modes. The anisotropic charge distribution surrounding atomic bonds can pave the way for coupling between phonons and the magnetic field.

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Section: Calculationssupporting

confidence: 92%

“…This spectrum, first calculated in ref 34. is in agreement with a recent X-ray experimental study48 . b Angle dependence of the phonon wave-vectors with a frequency of 20 cm −1 projected in the xz plane.…”

supporting

confidence: 90%

The phonon thermal Hall angle in black phosphorus

Machida

Subedi

et al. 2023

Nat Commun

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“…We report the first direct nanoscale measurement of CAP group velocities in the ZZ and AC crystalline directions. Our measurements are in excellent agreement with other calculations and non-localized measurements of acoustic phonon velocities [30,[41][42][43]. We also report the first observation of CAPs launched from flake edges in BP.…”

Section: Introductionsupporting

confidence: 90%

“…Like other 2D materials, the electronic properties of BP vary on the nanoscale, particularly flake edges [16], which impact the carrier-phonon interactions that generate and transport heat. Macroscopic or indirect measurements, such as theoretical calculations, ultrasonic measurements, and neutron and inelastic x-ray scattering measurements, report a wide range of acoustic phonon velocities in the in-plane Bravais lattice directions (ZZ direction, 7.4-9.6 km/s; AC direction 4.6-5.0 km/s [30,[41][42][43]), while in-plane phonon velocities in other directions are routinely calculated as linear-combinations of the ZZ and AC velocities by mode-averaging models. These wide distributions, combined with the absence of direct experimental observation of intrinsic vs edge-mediated phonon transport, once again raises the question of how nanoscale edge reconstruction may facilitate coherent phonon propagation in non-Bravais lattice directions.…”

Section: Introductionmentioning

confidence: 99%

Anomalous reduction in black phosphorus phonon velocities driven by lattice anisotropy

Joshi,

Unruh,

Mirzajani

et al. 2024

Preprint

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Phonon dynamics and transport determines how heat is utilized or dissipated in materials. In anisotropic 2D materials for miniaturized optoelectronics or thermoelectrics, the impact of material geometry and nanoscale material structure on phonon propagation is central to controlling thermal conduction. Here, we directly observe {in-plane} phonon propagation and dynamics in intrinsically anisotropic black phosphorus (BP) using ultrafast electron microscopy. We directly measure coherent acoustic phonon group velocities on the nanoscale along each of the Bravais lattice vectors (zigzag and armchair) and in an intermediate lattice direction that is a linear combination of the Bravais lattice vectors. We identify an anomalously low group velocity, deviating strongly from theoretical calculations, for coherent acoustic phonons travelling in the intermediate lattice direction. A machine learning-based model, calculating the phonon properties of an >8000 atom supercell, reveals the low group phonon velocity results from a mixing of the transverse and longitudinal acoustic phonons in BP that is independent of material morphology. This work demonstrates how transport of coherent phonons may be controlled through material geometry, while also highlighting how new avenues for directional control of nanoscale heat transport remain undiscovered even within well-known corrugated layered materials like BP.

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“…BP is a layered two-dimensional (2D) photocatalyst with visible near-infrared activity, layer-dependent bandgap, high carrier mobility, excellent mechanical resistance, biocompatibility and biodegradability, and high photothermal conversion efficiency. [1][2][3][4][5][6] However, the lone pair electrons on the phosphorus atoms of BP can react with oxygen and water molecules, which leads to diminishing the photocatalytic activity and ambient stability of BP. [7][8][9] Surface modication techniques such as covalent or non-covalent functionalizations, and metal-ion modication are common methods devoted to augmenting the ambient stability and photocatalytic activity of BP.…”

Section: Introductionmentioning

confidence: 99%