Naslov
SYNTHETIC FIELD-INDUCED CHARGE DENSITY WAVES

Autori
Radić, Danko

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, znanstveni

Skup
PCS IBS Seminar

Mjesto i datum
Daejeon, Republika Koreja, 10.01.2017

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Podatak o recenziji nije dostupan

Ključne riječi
charge density waves, synthetic magnetic field

Sažetak
The experimental discovery of charge density wave (CDW) on graphene sheets in intercalated graphite compound CaC6 [Rahnejat et al., Nature Commun. 2011] has drawn a lot of attention in physical community. Most importantly, the inability to explain the origin of such charge modulation via standard Fermi surface nesting mechanism, obviously implies the necessity to introduce new concepts in understanding the physics of density waves. Here, we propose a model in which we utilize lattice deformation-induced synthetic magnetic field, which influences electron dynamics via magnetic breakdown mechanism, to explain the onset of electron density modulation. The physical properties of graphene are significantly changed in CaC6 compound which is formed by intercalation of graphite with Ca atoms that form a hexagonal superlattice between graphene sheets. Also, they push the carbon sheets to 35% larger distance and dope them with 0.2 electrons per carbon atom, resulting in finite Fermi surface. The observed CDW appears along the underlying Ca ion lines and has period in perpendicular direction equal to three times that of the Ca superlattice, without measured displacement of carbon lattice. Taking all counted, the nesting mechanism to induce a CDW instability is ruled out. However, the observed density wave periodicity relates Fermi surfaces exactly to slightly overlapping position, having the new lattice unit cell 3√3a×√3a R30° (a is a carbon-carbon distance). Earlier, we proposed a mechanism by which the density wave can be induced by magnetic breakdown, that lowers total energy of the system in such configuration, due to an external magnetic field [Kadigrobov et al., PRL 2008]. Here, a slight, spontaneous, inplane deformation of carbon lattice may create a perpendicular synthetic magnetic field that can be large (few dozens Tesla). Electron tunneling assisted by that field (magnetic breakdown) connects closed electron orbits thus delocalizing electron motion and lowering its energy. The onset of density wave is a result of energy balance between electron condensate energy decrease due to the tunneling, and elastic energy "paid" to create the self-consistent synthetic magnetic field that assists the tunneling.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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