POSTECH LabCumentary Jee-Hoon Kim (Physics)
Magnetic Force Microscopy Laboratory
Magnetic Force Microscopy Laboratory
Jee-Hoon Kim (Physics)
In 2017, the international academic journal Nature Materials featured a paper titled ‘Violation of Ohm’s law in Weyl metal’. This was the first instance of a metal being discovered that did not follow Ohm’s law in 190 years. Ohm’s law, declared in 1827, outlines one of the most fundamental principles in physics that illustrates the relationship among current, voltage and resistance.
The Magnetic Force Microscope (MFM) Lab led by Professor Jeehoon Kim at the Department of Physics, POSTECH, became the world’s first to substantiate that the movement of electrons on the surface of Weyl metal was independent from the precepts of Ohm’s law. This monumental discovery could not have been made without the use of the magnetic force microscope (MFM), an instrument which the Lab single-handedly created.
A magnetic force microscope (MFM) is a cutting-edge device that uses a magnetic-coated probe to observe the magnetic properties of the sample. By measuring the magnetic force between the magnetized tip and the sample that measures only dozens of nanometers (1nm = one billionth of a meter), the MFM enables scientists to obtain magnetic information on the sample. There are only five or six laboratories equipped with MFM in the entire world, and only one such lab in Korea – the MFM Lab. Since these state-of-the art instruments are not commercially available, just creating an MFM alone is an extremely challenging research endeavor.
According to Professor Kim, we need to harness original observational equipment, such as the MFM, to identify and comprehensively understand novel physical phenomena. Professor Kim noted that “We have developed an MFM that operates at the ultra-low temperature of 4K (absolute temperature) and became the world’s first in 2017 to create a cryogenic vector magnetic field microscope that enables three-dimensional observations at the even lower temperature of 0.5K”.
Weyl metal is a new kind of topological metal and was first reported in academia as recently as 2013. The MFM Lab, while observing Weyl metal through its very own MFM, discovered that this metal did not follow the dictates of Ohm’s law. “Ohm’s law can be applied to generally all kinds of metal, which makes it unfit for use as an electronic element, such as semiconductor”, Professor Kim noted, and went on to say, “As we study the characteristics of Weyl metal and ensure that the electrons in it move about freely without being interrupted by impurities, then it becomes possible that we could actually create transistors from metal”.
A transistor is a sort of switch that controls voltage and current flow through the use of a semiconductor. The Digital Revolution of the 20th century arose along with the emergence of semiconductors and transistors, and they are widely accepted as the key components of the 4th Industrial Revolution. Professor Kim asserted that “If we could resort to metal over semiconductors as transistor materials, metal could be used as an electronic element”, and added that such a change ”could trigger a revolution in the field of electronic elements”.
In addition to the study of Weyl metal and other next-generation materials, the Lab is also planning to leverage MFM to observe and manipulate ‘Majorana fermions’ that are considered a promising candidate for qubit, the basic unit of quantum computing. Majorana fermions manifest themselves both as particles and an anti-particles, and Microsoft is looking into these as a possible qubit for quantum computing. Professor Kim reminds us that “As we engage in basic research to observe and manipulate Majorana fermions, the pathway towards developing commercial-level quantum computers will become all the more accessible”.
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