Control of near-field radiative heat transfer based on anisotropic 2D materials

Abstract

In this work, we study the near-field radiative heat transfer between two suspended sheets of anisotropic 2D materials. It is found that the radiative heat transfer can be enhanced with orders-of-magnitude over the blackbody limit for nanoscale separation. The enhancement is attributed to the excitation of anisotropic and hyperbolic plasmonic modes. Meanwhile, a large thermal modulation effect, depending on the twisted angle of principal axes between the upper and bottom sheets of anisotropic 2D materials, is revealed. The near-field radiative heat transfer for different concentrations of electron is demonstrated and the role of hyperbolic plasmonic modes is analyzed. Our finding of radiative heat transfer between anisotropic 2D materials may find promising applications in thermal nano-devices, such as non-contact thermal modulators, thermal lithography, thermosphotovoltaics, etc.Thermal radiation is an important physical phenomenon. Any object with temperature T>0K emits electromagnetic (EM) waves due to the fluctuating current generated from thermal motion of charge carriers. According to the Stefan-Boltzmann law, the radiative heat flux between two separated black bodies is given as 2 4 4 4 1 2 3 2 ( ) 60 B bb k S T T c π = −  , where k B is the Boltzmann constant,  is the reduced Planck's constant, c is the speed of light in vacuum, T 1 and T 2 is the high and low temperatures,respectively. For the Stefan-Boltzmann law, the separation distance d is much larger than the thermal wavelength λ th =c/k B T and only the propagation modes are taken into account in the process of radiative heat transfer. However, an additional contribution, i.e., evanescent waves, is dominant and should be considered when the separation distance d is much smaller than λ th (about 10 µm at room temperature). 1-2 The evanescent waves near the surface can be surface plasmon polaritions (SPPs), 3 surface phonon polaritions (SPhPs), 3,4 or even frustrated modes from hyperbolic materials. 5-6 Due to large density of states of evanescent waves, near-field radiative heat transfer (NFRHT) can exceed the blackbody limit by several orders of _____________________________ a) Author to whom correspondence should be addressed. Electronic

Magnetoplasmonic manipulation of nanoscale thermal radiation using twisted graphene gratings

“… is the component of the wave vector parallel to the interface. () is the energy transmission coefficient, which reads [67,70,73]…”

The Optical Properties and Plasmonics of Anisotropic 2D Materials

“…Because of their unique plasmon dispersion, the hyperbolic plasmons can propagate in a certain direction with a large density of states and higher filed confinement, leading to applications of spontaneous radiation enhancement, hyperlens, negative index materials, and thermal management . Many of these have been realized in hyperbolic metasurfaces, created by artificial subwavelength structuring from visible to microwave frequency ranges .…”

Nonreciprocal radiative heat transfer between two planar bodies

“…Understanding radiative heat transfer [1][2][3] is essential in many applications ranging from radiative cooling [4][5][6] and thermal diodes [7] to thermal transistors [8][9][10][11] and thermophotovoltaic systems [12][13][14][15][16]. The majority of works investigating radiative heat transfer consider materials that satisfy Lorentz reciprocity [17][18][19][20][21][22][23][24][25][26][27][28][29][30]. On the other hand, it is known that breaking the constraint of reciprocity is necessary in order to reach the thermodynamic limit of thermal radiation harvesting [31][32][33].…”