Research On The Effect Of Graphene Plasmons In Near-field Radiative Heat Transfer

Nowadays,the increasing demand for sustainable energy leads to an urgent need for alternative energy harvesting methods with better performance than current technologies.Near-field radiative heat transfer is one of the most promising routes for boosting the efficiency and power output of energy harvesting systems.It has been shown that when two objects at different temperatures are brought within a distance much smaller than the characteristic wavelength of thermal radiation,the radiative heat flux can exceed the well-known blackbody limit.This effect is caused by the coupling of evanescentwaves that opens the paths for photons to tunnel,which called the photon tunneling.Therefore,radiative heat transfer in near-field region has gained interests theoretically and experimentally in the past decades.It has widely application in thermal imaging,radiative cooling,near-field thermophotovoltaics and thermal energy conversion.Various systems have been proposed to enhance the near-field heat transfer as well.There are many materials like metamaterials,hyperbolic metamaterials and SiC-covered metamaterials have been presented to improve the near-field radiation transfer.We should continue to study new material and structure to solve the transmission of thermal photovoltaic devices.The radiation transfer of THz wave is also an interesting research.Particularly,studies on the enhancement and modulation of radiation transfer of THz waves in near-field regime are necessary.Surface waves,such as surface phonon-polaritons(SPhPs)and surface plasmons(SPs),can efficiently enhance radiative heat transfer.The finite conductivity of metal or high absorption coefficient of dielectric material can cause high energy loss,however,the appearance of graphene makes up for the deficiency of metal and graphene is believed to be a promising surface plasmonic material from the terahertz to the mid-infrared spectral region.Graphene is composed of monolayer carbon atoms arranged in honeycomb lattices and has attracted considerable attention in recent years because of its excellent optical and electronic properties.Compared with SPPs on noble metals,graphene surface plasmon polaritions(GSPPs)could confine EM field at an extremely subwavelength scale in the mid-infrared spectral region.Moreover,GSPPs could be actively tuned by external bias voltage or chemical doping.In this paper,we introduced several new structures based on the graphene forimproving near-field radiative heat transfer.Firstly,the near-field radiative heat transfer between graphene-covered metamaterials is investigated.The electric surface plasmons(SPs)supported by metamaterials can be coupled with the SPs supported by graphene,which enhances the near-field heat transfer.Then,we study the contribution of terahertz waves to near-field radiation transfer by graphene-based hyperbolic metamaterials structure.Because of the presence of a continuum of hyperbolic modes,the radiation heat transfer can also be enhanced remarkably in the total THz range for our proposed structure.Meanwhile,we demonstrate that the radiation transfer can be actively controlled by means of graphene surface plasmon polaritions.Finally,study the coupling of surface plasmons in terms of two monolayer conplane graphene nanoribbons to design high-speed and ultra-compact terahertz devices.