On August 24, the international academic journal Nature Physics published on line the research results of Professor Wang Zenghui and Xia Juan of University of Electronic Science and technology of China. With the aid of a diamond anvil cell (DAC), which can generate 1 million atmospheres of pressure, they have carried out extremely high pressure research on two-dimensional heterojunction materials which are only one thousandth of the thickness of cicada wings. < / P > < p > in the research, scientists have skillfully utilized the structural characteristics of two-dimensional heterojunction to achieve efficient compression of nanomaterials with atomic thickness, and observed a series of novel physical phenomena. < / P > < p > “diamond anvil cell is a very powerful experimental method because it has unique advantages in applying ultra-high pressure to micro samples.” Xia Juan said. < / P > < p > the main part of the diamond anvil device is two sharp diamonds (diamond anvil) and a gasket that surrounds the very small space between the two diamond tips (also known as the anvil surface). < / P > < p > “when we push the two diamonds in the diamond anvil towards each other, the space between the diamond tips is sharply compressed, and the space is filled with liquid pressure medium (such as silicone oil) in addition to the sample.” Xia Juan explained that because the gasket is like a hoop, tightly hooping these liquid pressure transmission media, so that there is no place to release, so the pressure in the space where the sample is located will rise sharply, thus exerting a huge hydrostatic pressure on the sample, similar to the increasing sea water pressure when diving into the deep sea. < p > < p > the reporter has learned that since the diameter of the anvil surface at the top of the diamond is very small, usually only a fraction of a millimeter, that is, the diameter of almost 4-8 hair wires, so that the pressure on the bottom plane of the diamond can be effectively concentrated, so as to achieve a high pressure at the top of the diamond. The pressure of our daily living environment is 1 atm, and the pressure of 10 000 m on the sea floor is about 1000 ATM. With this device, we can easily realize a high pressure environment of 1 million ATM. < / P > < p > what is the pressure of one million atmospheres? People often jokingly say that “the pressure mountain is great”. Let’s take Mount Tai as an example to estimate. The main peak of Mount Tai is 1450 meters high. If the rock density is 3 times of water, it will be pressed at the bottom of the mountain. The pressure from the mountain is more than 400 atmospheres. Therefore, “heavier than Mount Tai” is far from enough to describe the pressure produced by diamond on anvil. < / P > < p > two dimensional materials are a kind of new materials which are widely concerned at present. The most significant feature of 2D materials is that they can be as thin as atoms, and can still maintain excellent material properties. How thin is “atomic level”? A typical cicada wing is a few microns thick (that is, about one tenth of the hair silk), while the two-dimensional materials studied by physicists are generally nanometer in thickness, even less than one thousandth of that of cicada wings. Therefore, “as thin as a cicada wing” is far from enough to describe the thin of two-dimensional materials. What is a two-dimensional heterojunction? “Structurally, it can be understood as stacking different two-dimensional materials in a specific way to form a new two-dimensional material, similar to sticking two (or more) different” cicada wings “together to form a new” composite cicada wing. ” Wang Zenghui said. < / P > < p > for scientists, all kinds of two-dimensional materials are like Lego building blocks: by choosing different two-dimensional materials and different stacking methods, all kinds of novel LEGO works – two-dimensional heterojunction can be formed. This means that almost unlimited kinds of novel two-dimensional structures can be designed artificially, and each structure may have different material physical properties. Therefore, in many research fields, two-dimensional heterojunction is a kind of new material structure with great potential. Xia Juan said: “this study is a little similar to putting a two-dimensional heterojunction cicada wing in the middle of a 10000 ton hydraulic press to make the two” cicada wings “fit more closely by using the extremely high pressure which is heavier than Mount Tai, so as to change the interaction between the two layers of” cicada wings “, and observe the regulation effect of this process on the performance of the whole” composite cicada wing “. It’s just that we’re doing this at a nanoscale < / P > < p > during the experiment, the research team confirmed that although the thickness of the two-dimensional heterojunction is at the atomic level, due to its structural characteristics, it can still be further compressed by the pressure generated by the diamond anvil device. When the ambient pressure of the sample increases to about 10000 atmospheres, the researchers have successfully observed the abrupt changes in the band structure and related physical properties of the two-dimensional heterojunction. < / P > < p > “although this work is a very basic physical research, from the application point of view, it is also of great scientific significance and application value to carry out the research on the physical characteristics of new sensitive materials under high pressure for the development of new ultra-high pressure sensors, promoting the progress of China’s deep-sea exploration technology, and accelerating the industrial development of shale gas and other modern energy strategies Value. ” Wang Zenghui said. Global Tech