American physicists have described the device is a rectifying antenna, which uses no diodes. This design is more sensitive and energy efficient, and in the future with its help, you can recharge mobile device from radio waves. In addition, it eliminates the terahertz gap. Article published in the journal Science Advances.
In the mid-twentieth century was invented a method of producing DC power from radio waves. It requires rectenna — rectifying antenna. In its construction, use diodes that allow current only in one direction. The problem is that the diodes have two fundamental disadvantages. First, they have a threshold minimum voltage for actuation, that is, either the radio emission must be very powerful, or the antenna is large. Second, the current through them begins to flow only after a short time after its filing, that prevents the use of high frequency.
These and other problems reduce the efficiency of generating electricity from radio waves, although some modern miniature devices consume microwatt energy, and hypothetically they could be powered from the router or even use remote charging of mobile devices. In addition, between the operating frequencies of your pictures and radiationof gaps exist, which currently are difficult to detect waves in the range from 0.1 to 10 terahertz.
A group of scientists from the Massachusetts Institute of technology under the leadership of Hiroki Isobe (Isobe Hiroki) proposed an alternative design rectenna that do not use diodes. Instead, they propose to use a nonlinear electric response of non-centrosymmetrical crystals.
The fact that some materials produce a DC current when placed in an external oscillating electric field. They have no minimum voltage to trigger, no delay. Because the nonlinear electric response occurs including the terahertz and infrared radiation, terahertz bezdomnye rectenna eliminate the gap and can replace bolometersare used to detect infrared radiation, but also triggered with a delay.
A key element of this technology is non-centrosymmetrical crystals are chiral, that is, those whose one half is not equal to the specular reflection of the second. The authors proposed to create such crystals of graphene due to its conductive properties, but at the same time in pure form it is symmetrical. For the violation of this symmetry can be single layer graphene to augment the substrate of boron nitride, or three layers folded so that the atoms in the resulting crystal, formed an irregular triangle. If the material of these crystals attach the antenna, it will be effective to produce a current from radio waves, even if they are weak.
Recently, graphene has also made savetogether and anomalous magnet. On the effect similar to the nonlinear electric response, the nonlinear optics, which could create a cheap detector for two-dimensional materials.