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TT: Fachverband Tiefe Temperaturen

TT 84: Focus Session: Emerging Magnetic Phenomena from Chiral Phonons II (joint session MA/TT)

TT 84.1: Talk

Friday, March 22, 2024, 09:30–09:45, H 1058

Born effective charges in insulators and metals — •Paolo Fachin, Francesco Macheda, and Francesco Mauri — Sapienza, Università di Roma, Italia

The Born effective charges quantify the coupling of phonons with light, allowing to describe experimental spectra of crystals in infrared spectra. While in insulators the electrical polarization is well defined and the Born Effective charges are described in a Berry phase formulation in the context of the modern theory of polarization[1], in metals this quantity is more challenging to deal with. There are two different limits, the static [2] and the dynamical [1][3] one, concurring in the determination of the vibrational features in a combination depending on the phonon frequency and linewidth ratio [4]. The nature of these two limits is clarified using a low energy model for graphene compared with ab initio simulations. The effect of the recently predicted [5][6] intrinsic chiral phonons in crystals can be detected in infrared experiments in a way that is described by the Born effective charges.

[1] Bistoni,Mauri et al., 2D Materials, 6, 045015 (2019)

[2] Macheda, Barone and Mauri, Phys.Rev.Lett.,129(18),185902(2022)

[3] Dreyer,Coh, and Stengel, Phys. Rev. Lett., 128, 095901 (2022)

[4] Marchese, Macheda, Mauri and al., Nat. Phys. (2023)

[5] Bistoni, Mauri, and Calandra, Phys.Rev.Lett. 126,225703 (2019)

[6] Saparov, Niu et al., Phys. Rev. B 105, 064303 (2022)

Keywords: Phonons; Chiral Phonons; Born Effective Charges; Infrared spectroscopy