Graphene-Based Modulation and Enhancement of Near-Field Radiative Heat Transfer Rectification

Two bodies at different temperatures experience a radiative heat transfer mediated by the electromagnetic field even when they are separated by vacuum. While this energy transfer is limited by Stefan-Boltzmann's law at large separation distances, in the second half of the 20th century the development of fluctuational electrodynamics has theoretically shown that it can be enhanced in a spectacular fashion in the near field [1,2] (distances in the micron range and below around ambient temperature), in particular in the case of polar materials supporting resonant surface modes of the electromagnetic field such as surface phonon polaritons [2]. Since then, these theoretical predictions have been confirmed by a large number of experiments, involving different geometries and temperature ranges, and stimulating in turn further theoretical investigations (see [4] and references therein).<br/>These developments have paved the way to the exploration of the role played by near-field radiative heat transfer in a variety of applications, including heat-assisted data recording, infrared spectroscopy, energy conversion techniques and thermotronics, i.e. the design of thermal equivalent of circuit elements.<br/>In this context a significant attention has been devoted to the rectification of radiative heat flux in the near field [5], consisting in a configuration implying a strong asymmetry of heat flux when exchanging the temperatures of the two bodies. This behavior has been explored by exploiting phase-change materials [6-14], superconductors [15,16] or many-body effects [17].<br/>In our work we consider a system made of two parallel films, made of silica and vanadium dioxide, a metal-insulator phase-change material with a transition around ambient temperature. We show that, by covering both films with a graphene sheet and by acting on the chemical potential of both graphene sheets, the efficiency of such a device can be strongly modulated and more specifically enhanced by up to 14% at a separation distance of 100 nm. More specifically, our system is expected to reach an efficiency of 85%, among the best recently proposed rectification systems in the same distance and temperature ranges. By studying the dependence on the separation distance and the graphene chemical potential along with the flux spectral features, we highlight the crucial role played by graphene plasmons in the increased coupling between the two films. These results pave the way to the active manipulation of heat flux at the nanoscale.<br/><b>References</b><br/>[1] S. M. Rytov, Y. A. Kravtsov, and V. I. Tatarskii, <i>Principles of Statistical Radiophysics</i> (Springer, New York, 1989).<br/>[2] D. Polder and M. van Hove, Phys. Rev. B <b>4</b>, 3303 (1971).<br/>[3] K. Joulain, J.-P. Mulet, F. Marquier, R. Carminati, and J.-J. Greffet, Surf. Sci. Rep. <b>57</b>, 59 (2005).<br/>[4] S.-A. Biehs, R. Messina, P. S. Venkataram, A. W. Rodriguez, J. C. Cuevas, and P. Ben-Abdallah, Rev. Mod. Phys. <b>93</b>, 025009 (2021).<br/>[5] C. R. Otey, W.T. Lau, and S. Fan, Phys. Rev. Lett. <b>104</b>, 154301 (2010).<br/>[6] P. van Zwol, K. Joulain, P. Ben-Abdallah, and J. Chevrier, Phys. Rev. B <b>84</b>, 161413(R) (2011).<br/>[7] P. Ben-Abdallah, S.-A. Biehs, Appl. Phys. Lett. <b>103</b>, 191907 (2013).<br/>[8] W. Gu, G.-H. Tang, W.-Q. Tao, Int. J. Heat Mass Transf. 82, 429 (2015).<br/>[9] Y. Yang, S. Basu, and L. P. Wang, J. Quant. Spectrosc. Radiat. Transfer 158, 69 (2015).<br/>[10] A. Ghanekar et al., Opt. Express <b>26</b>, A209 (2018).<br/>[11] F. Chen, X. Liu, Y. Tian, and Y. Zheng, Adv. Eng. Mater. <b>23</b>, 2000825 (2021).<br/>[12] K. Ito, K. Nishikawa, A. Miura, H. Toshiyoshi, and H. Iizuka, Nano Lett. <b>17</b>, 4347 (2017).<br/>[13] A. Fiorino et al., ACS Nano <b>12</b>, 5774 (2018).<br/>[14] I.Y. Forero-Sandoval et al., Phys. Rev. Applied <b>14</b> 034023 (2020).<br/>[15] J. Ordonez-Miranda et al., J. Appl. Phys. <b>122</b>, 093105 (2017).<br/>[16] E. Moncada-Villa and J. C. Cuevas, Phys. Rev. Appl. <b>15</b>, 024036 (2021).<br/>[17] I. Latella and P. Ben-Abdallah, Phys. Rev. B <b>104</b>, 045410 (2021).