Sonntag Jens, Reichardt Sven, Beschoten Bernd, Stampfer Christoph
JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany.
Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, 52425 Jülich, Germany.
Nano Lett. 2021 Apr 14;21(7):2898-2904. doi: 10.1021/acs.nanolett.0c05043. Epub 2021 Apr 2.
We explore the tunability of the phonon polarization in suspended uniaxially strained graphene by magneto-phonon resonances. The uniaxial strain lifts the degeneracy of the LO and TO phonons, yielding two cross-linearly polarized phonon modes and a splitting of the Raman G peak. We utilize the strong electron-phonon coupling in graphene and the off-resonant coupling to a magneto-phonon resonance to induce a gate-tunable circular phonon dichroism. This, together with the strain-induced splitting of the G peak, allows us to controllably tune the two linearly polarized G mode phonons into circular phonon modes. We are able to achieve a circular phonon polarization of up to 40% purely by electrostatic fields and can reverse its sign by tuning from electron to hole doping. This provides unprecedented electrostatic control over the angular momentum of phonons, which paves the way toward phononic applications.
我们通过磁声子共振研究了悬浮单轴应变石墨烯中声子极化的可调性。单轴应变消除了纵光学（LO）声子和横光学（TO）声子的简并，产生了两个交叉线性极化的声子模式以及拉曼G峰的分裂。我们利用石墨烯中强的电子-声子耦合以及与磁声子共振的非共振耦合来诱导栅极可调的圆声子二向色性。这与应变诱导的G峰分裂一起，使我们能够可控地将两个线性极化的G模式声子调谐为圆声子模式。我们仅通过静电场就能实现高达40%的圆声子极化，并且通过从电子掺杂调谐到空穴掺杂可以反转其符号。这提供了对声子角动量前所未有的静电控制，为声子应用铺平了道路。
