Last blog mentioned metallic hydrogen at a very small level. As the computational power increases, we are able to examine (theoretically at least) the behavior of various materials. There is a significant amount of effort being directed at the investigation of a new state of matter of metals, defined as “strange metals”, which actually involves understanding the behavior of the electrons.
The difference from traditional understanding of metals, is that “strange” metals have electrical resistance directly linked to its temperature. The conductivity is linked to both Planck’s constant and Boltzmann’s constant. [Ref. 1] Planck’s constant establishes the energy a photon can have, while the Boltzmann constant is the relationship of the kinetic energy of particles in a gas with temperature of the gas.
According to Reference 2, a robust computational model of “strange’ metals provided sufficient details to classify these “strange” metals existing in a new state of matter. Their explanation of “strange” metals is that the name is generated base on the behavior of electrons in the metal. In metals, electrons travel freely in the material with little resistance and few interactions. “Strange” metal electrons are more restricted and slower moving that would be anticipated. In effect, “strange” metals are not metal nor insulator. The referenced article also employs the term “reluctant” metals.
This discovery is a result of research on high-temperature super-conductivity [Ref. 3] In 1990, researchers discovered that cuprates have a strange behavior that does not vary with temperature as anticipated or as other high temperature super-conductors. Current theory can explain superconducting properties below 30 K, but that property up to temperatures of 130 K was puzzling. Fermi liquid theory predicts that at low temperatures, the metal resistance should depend on the square of the temperature. Cuprates resistance varies linearly down to when they become superconducting. This testing has been performed at a wide range of temperatures and with field strengths of up to 80 T (tesla).
Some research at TU Wien (Vienna University of Technology) is focused on developing higher temperature super conducting materials [Ref. 4]. They have been using ytterbium, rhodium, and silicon (YbRn2Si2), which is know for its “strange” properties. They are using a new molecular beam epitaxy (MBE) process. They build the layers of the material atomic layer by atomic layer. (A side issue was to create the substrate for building the material. Germanium turns out to be a geometrical match for the structure of the new material. They have found that a sudden change in the carrier concentration induces the “strange” metal state. Significant additional work needs to be done to understand the state of the materials before any development can proceed.
The implications of this work are many. While the mention of super conductivity has been basis for projections of high speed transport via magnetic levitation, the increase in conductivity could increase the effective amount of electrical power for everyone. Currently, the transmissions losses are significant and being able to almost eliminate the losses would effectively increase the electrical power available. This type of application becoming mainstream is based on atomic level precision and methods of building materials layer by atomic layer. That ability to create very large amounts of the material is still a few years in the future. Tools need to be developed and techniques for measuring and evaluating the resultant materials need to be developed. This is part of the continual search for new material properties starting at the atomic and nanometer sizes.