If the fractional quantum Hall regime were a series of highways, these highways would have either two or 4 lanes. The flow of the two-flux or four-flux composite fermions, like automobiles on this two- to four-flux composite fermion traffic scenario, naturally explain the greater than 90 fractional quantum Hall states that form in a big number of host materials. Physicists at Purdue University have recently discovered, though, that fractional quantum Hall regimes usually are not limited to two-flux or four-flux and have discovered the existence of a brand new form of emergent particle, which they’re calling six-flux composite fermion. They’ve recently published their groundbreaking findings in Nature Communications.
Gabor Csathy, professor and head of the Department of Physics and Astronomy on the Purdue University College of Science, together with PhD students Haoyun Huang, Waseem Hussain, and up to date PhD graduate Sean Myers, led this discovery from the West Lafayette campus of Purdue. Csathy credits lead creator Huang as having conceived, led the measurements and writing a big a part of the manuscript. All of the ultra-low-temperature measurements were accomplished in Csathy’s Physics Constructing lab. In his lab they conduct research on strongly correlated electron physics, sometimes known as topological electron physics.
Weak interactions of electrons are well established, and the behavior is kind of predictable. When electrons interact weakly, the electron is often considered the natural constructing block of the whole system. But when the electrons interact strongly, interpreting the systemic behavior by pondering of individual electrons becomes nearly not possible.
“This happens in only a few instances, like within the fractional quantum Hall regime which we study, for instance,” says Csathy. “To elucidate fractional quantum Hall states, the composite fermion, a really intuitive fundamental constructing block, comes in numerous flavors. They’ll account for a complete subset of the fractional quantum Hall states. But all of the fully developed, (i.e topologically protected), fractional quantum Hall states may very well be accounted for by only two forms of composite fermions: the two-flux and four-flux composite fermions. Here we reported a brand new fractional quantum Hall state that can not be explained by any of those previous ideas! As a substitute, we want to invoke the existence of a brand new form of emergent particle, the so-called six-flux composite fermions. The invention of latest fractional quantum Hall states is scarce enough. Nevertheless, the invention of a brand new emergent particle in condensed matter physics is really rare and amazing.”
For now, these ideas will likely be used to expand our understanding of the ordering of the known fractional quantum Hall states right into a “periodic table.” It is very notable to this process that the emergent composite fermion particle is exclusive in that the electron captures six quantized magnetic flux quanta, forming probably the most intricate composite fermion known to this point.
“The numerology of this complicated physics puzzle requires quite some patience,” says Haoyun Huang, Csathy’s PhD student. “Take the nu=2/3 fractional state for instance. Since 2/3=2/(2*2-1), the nu=2/3 state belongs to the two-flux family. Similarly, for the nu=2/7 fractional state, 2/7=2/(2*4-1), so this state belongs to the four-flux family. In contrast, the fractional states we discovered closely relate to 2/11=2/(2*6-1). Before our work, no fully quantized fractional quantum Hall state was seen that may very well be related to six-flux composite fermions. The situation was completely different on the speculation front: The existence of those sorts of composite fermions was predicted by Jainendra Jain in his highly influential theory of composite fermions published in 1989. The associated quantization was not observed during these 34 years.”
The fabric utilized in this study was grown by a Princeton University team led by Loren Pfeiffer. The GaAs semiconductor electrical quality played an enormous role within the success of this research. In line with Csathy, this Princeton group is leading the world in growing the best quality GaAs-based materials.
“The GaAs they grow may be very special, because the variety of imperfections is astonishingly low,” he says. “The mix of low disorder and the ultra-low-temperature measurement expertise within the Csathy lab made this project possible. One reason we were measuring these samples is that very recently the Princeton group has significantly improved the standard of the GaAs semiconductor, as measured by the tiny amounts of defects present. These improved samples will, needless to say, proceed to constitute a playground for brand new physics.”
This exciting discovery is an element of ongoing research by Csathy’s team. The team continues to push the boundaries of discovery of their persistent pursuit of topological electron physics.
Low-temperature measurements in Csathy’s lab were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences program, under Award No. DE-SC0006671. Sample growth efforts of the Princeton team were supported by the Gordon and Betty Moore Foundation Grant No. GBMF 4420 and the National Science Foundation MRSEC Grant No. DMR-1420541.
