Ca2N is a layered material that has been recently identified as a two-dimensional (2D) electride, an unusual ionic compound in which electrons serve as anions. The electronic properties of 2D electrides attract considerable interest as the anionic electrons, which form a 2D layer sandwiched between atomic planes, are highly mobile as they are not attached to any ion. Here, on the basis of first-principles time-dependent density-functional theory calculations, we investigate the collective excitations of the electrons - i.e., the plasmons - in Ca2N as a function of wave vector q. Our calculations reveal an intrinsic negative in-plane dispersion of the anionic plasmon, in striking contrast with the homogeneous electron gas. Moreover, for wave vectors q normal to the planes, we find a long-lived plasmon that continues to exist well beyond the first Brillouin zone. This is a mark of the electronic inhomogeneities in the charge response that Ca2N shares with other layered materials like transition-metal dichalcogenides and MgB2. Finally, we compare the plasmon properties of Ca2N in its bulk and monolayer forms, which shows the effect of the different electronic structures and dimensionalities.

Collective charge excitations of the two-dimensional electride Ca2 N / Cudazzo, P.; Gatti, M.. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 96:12(2017). [10.1103/PhysRevB.96.125131]

Collective charge excitations of the two-dimensional electride Ca2 N

Cudazzo P.;
2017-01-01

Abstract

Ca2N is a layered material that has been recently identified as a two-dimensional (2D) electride, an unusual ionic compound in which electrons serve as anions. The electronic properties of 2D electrides attract considerable interest as the anionic electrons, which form a 2D layer sandwiched between atomic planes, are highly mobile as they are not attached to any ion. Here, on the basis of first-principles time-dependent density-functional theory calculations, we investigate the collective excitations of the electrons - i.e., the plasmons - in Ca2N as a function of wave vector q. Our calculations reveal an intrinsic negative in-plane dispersion of the anionic plasmon, in striking contrast with the homogeneous electron gas. Moreover, for wave vectors q normal to the planes, we find a long-lived plasmon that continues to exist well beyond the first Brillouin zone. This is a mark of the electronic inhomogeneities in the charge response that Ca2N shares with other layered materials like transition-metal dichalcogenides and MgB2. Finally, we compare the plasmon properties of Ca2N in its bulk and monolayer forms, which shows the effect of the different electronic structures and dimensionalities.
2017
12
Cudazzo, P.; Gatti, M.
Collective charge excitations of the two-dimensional electride Ca2 N / Cudazzo, P.; Gatti, M.. - In: PHYSICAL REVIEW. B. - ISSN 2469-9950. - 96:12(2017). [10.1103/PhysRevB.96.125131]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/357564
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