Abstract
Interlayer van der Waals (vdW) coupling is generic in two-dimensional materials such as graphene and transition-metal dichalcogenides, which can induce very low-energy phonon modes. Using high-resolution inelastic hard x-ray scattering, we uncover the ultralow energy phonon mode along the Cu-O bond direction in the high-Tc cuprate (Bi,Pb)2(Sr,La)2CuO6+δ (Bi2201). The energy and full-width half-maximum (FWHM) of these modes are independent of temperature, while their intensity decreases with doping in accordance with an increasing c-axis lattice parameter. We compare the experimental results to first-principles density functional theory simulations and identify the observed mode as a van der Waals phonon, which arises from the shear motion of the adjacent Bi-O layers. This shows that Bi-based cuprate has vibrational properties similar to graphene and transition-metal dichalcogenides, which can be exploited to engineer novel heterostructures.
Original language | English (US) |
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Article number | 024804 |
Journal | Physical Review Materials |
Volume | 8 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2024 |
ASJC Scopus subject areas
- General Materials Science
- Physics and Astronomy (miscellaneous)