Kravtsov M, Shilov A L, Yang Y, Pryadilin T, Kashchenko M A, Popova O, Titova M, Voropaev D, Wang Y, Shein K, Gayduchenko I, Goltsman G N, Lukianov M, Kudriashov A, Taniguchi T, Watanabe K, Svintsov D A, Adam S, Novoselov K S, Principi A, Bandurin D A
Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore.
Institute for Functional Intelligent Materials, National University of Singapore, Singapore, Singapore.
Nat Nanotechnol. 2025 Jan;20(1):51-56. doi: 10.1038/s41565-024-01795-y. Epub 2024 Oct 7.
Light incident upon materials can induce changes in their electrical conductivity, a phenomenon referred to as photoresistance. In semiconductors, the photoresistance is negative, as light-induced promotion of electrons across the bandgap enhances the number of charge carriers participating in transport. In superconductors and normal metals, the photoresistance is positive because of the destruction of the superconducting state and enhanced momentum-relaxing scattering, respectively. Here we report a qualitative deviation from the standard behaviour in doped metallic graphene. We show that Dirac electrons exposed to continuous-wave terahertz (THz) radiation can be thermally decoupled from the lattice, which activates hydrodynamic electron transport. In this regime, the resistance of graphene constrictions experiences a decrease caused by the THz-driven superballistic flow of correlated electrons. We analyse the dependencies of the negative photoresistance on the carrier density, and the radiation power, and show that our superballistic devices operate as sensitive phonon-cooled bolometers and can thus offer, in principle, a picosecond-scale response time. Beyond their fundamental implications, our findings underscore the practicality of electron hydrodynamics in designing ultra-fast THz sensors and electron thermometers.
入射到材料上的光会引起其电导率的变化，这种现象被称为光电阻。在半导体中，光电阻是负的，因为光诱导电子穿过带隙会增加参与输运的载流子数量。在超导体和普通金属中，光电阻分别是正的，这是由于超导态的破坏和动量弛豫散射增强。在这里，我们报道了掺杂金属石墨烯中与标准行为的定性偏差。我们表明，暴露在连续太赫兹（THz）辐射下的狄拉克电子可以与晶格热解耦，从而激活流体动力学电子输运。在这种情况下，石墨烯缩颈处的电阻会因太赫兹驱动的关联电子超弹道流而降低。我们分析了负光电阻对载流子密度和辐射功率的依赖性，并表明我们的超弹道器件作为灵敏的声子冷却测辐射热计工作，因此原则上可以提供皮秒级的响应时间。除了其基本意义外，我们的发现强调了电子流体动力学在设计超快太赫兹传感器和电子温度计方面的实用性。
