Electrical control of intervalley scattering in graphene via the charge state of defects

Abstract

We study the intervalley scattering in defected graphene by low-temperature transport measurements. The scattering rate is strongly suppressed when defects are charged. This finding highlights "screening" of the short-range part of a potential by the long-range part. Experiments on calciumadsorbed graphene confirm the role of a long-range Coulomb potential. This effect is applicable to other multivalley systems, provided that the charge state of a defect can be electrically tuned. Our result provides a means to electrically control valley relaxation and has important implications in valley dynamics in valleytronic materials.

Electrical band flattening, valley flux, and superconductivity in twisted trilayer graphene

“…It can be observed clearly that sizable valley currents appear in regions in the complementary regions to the low-energy states, similarly to other moiré systems [22,56]. Since the emergence of such currents relies on valley conservation, terms in the system creating intervalley mixing are expected to substantially impact them [6,[65][66][67], as we address in the next section.…”

Engineering Valley Polarization of Monolayer WS2: A Physical Doping Approach

“…The intervalley scattering process of exciton is governed by electron–hole exchange interaction through the Maialle–Silva–Sham mechanism, resulting in short valley lifetime in picosecond scale . In the previous studies by electrically tailoring the doping states in graphene, the intervalley scattering rate was strongly suppressed . This carrier doping approach was proposed to be applicable to other multivalley systems like TMDs.…”

Spontaneous Valley Spirals in Magnetically Encapsulated Twisted Bilayer Graphene

“…For example, a valley magnet (hv z I i ≠ 0) acts as a valley filter and can be used to suppress the valley Hall signal for one valley but not the other. In our case, we expect the planar valley spiral (hv z I i ¼ 0) to act as a "coherent valley mixer" [85][86][87]. This would strongly suppress the valley Hall signal when the chemical potential is swept to approach half filling of the flatband, thus providing an experimental signature for spontaneous valley mixing.…”