The research group of Professor Liu Hongwu of Jilin University has discovered a new topological particle magnetic domain Wall Smingzi Vigner solid

Recently, Professor Liu Hongwu's research group of the State Key Laboratory of Superhard Materials of Jilin University has made new progress in the field of condensed matter topology research, and the relevant results were published in Nature Communications on October 14, 2021 under the title of "Wigner solids of domain wall skyrmions".

Topological insulator is a new type of material with surface conductive electricity and internal insulation and symmetrical protection topological sequence (its topologicality stems from the unique band structure of the material in the inverted space), and has a wide range of application prospects in the fields of spintronics and quantum computing (the research of topological phase transition was awarded the 2016 Nobel Prize in Physics). With the continuous deepening of the research on topological insulators, the application of topological concepts in condensed matter systems has attracted much attention in recent years, the most representative of which is chiral magnets. Chiral magnets are a class of magnetic materials with inverse symmetry fractures, and the topological spin structure is formed by the chiral interaction induced by spin-orbit coupling, the magnetic Schminsteron (left). Magnetosters and topological insulators are the concrete embodiment of topological properties in real space and reversible space, respectively. As a topological particle that can be directly observed in real space, its novel quantum characteristics are of great significance for the preparation of new magnetic storage devices with high density, high speed and low power consumption. In addition to the magnetos found in chiral magnets, the theory predicts that sigmines may also form a new topological particle in the domain wall, the magnetic domain wall sigminon (right). Since magnetic domain walls are widely present in many fields such as cosmology, string theory, high-energy physics and condensed matter physics, the experimental discovery of magnetic domain walls will greatly expand the dimension and physical space of the existence of smarters, and the detection and study of their characteristics have important theoretical and practical significance in the above fields.

In order to realize the experimental observation of this new topological particle, Liu Hongwu's research group cleverly combined the resistive nuclear magnetic resonance (RDNMR) and non-local resistance measurement with ultra-high detection sensitivity to create a new non-local resistive nuclear magnetic resonance measurement (NRDNMR) technology (national invention patent: CN202011028664.0). This technology not only increases the detection sensitivity by an order of magnitude, but more importantly eliminates the Effect of Hall bias caused by electrical measurements under magnetic field conditions, thereby enabling damage-free detection of the intrinsic properties of quantum states. The researchers used the technique to discover this new topological particle in the quantum Hall ferromagnetic (QHF) magnetic domain wall formed by the InSb quantum well, and the important results include:

1. Discovery of ground-state magnetic domain wall Scrimminer Theory predicts that magnetic domain wall Sgminzi exist in the form of excited states of magnetic domain walls. This study shows that the equivalence of topological and physical charges in the QHF state gives the magnetic domain Dsgminon "chargability" and the formation of one-dimensional Vigner crystals (i.e., in the ground state) through long-range Coulomb interactions.

2. Achieve high-temperature Vigner crystal Compared with the semiconductor electrons or hole Wigner crystals formed at mk temperature, the magnetic domain wall Sigmin Vigner crystal can remain stable at 4k temperature. This temperature is expected to be further improved by pressure-regulating spin-orbit interactions that control topological particle size and spacing.

3. Regulation of topological phase transition Experiments have found that by adjusting the effective magnetic field between landau energy levels, the phase transition of topological magnetic domain wall Schweiminder crystals, vitreous bodies and non-topological spin waves can be realized. This topological system provides a new platform for studying quantum criticality.

It should be pointed out that the InSb quantum well device used in the above experiment has a history of more than 30 years. In 2017, the research group successfully revealed the important influence of quantum Hall edge chirality on nuclear spin polarization based on the same sample, and opened the door to the application of edge state chirality in nuclear spintronics [Nat.Commun. 8, 15084(2017)】。 After years of unremitting efforts, researchers have re-energized this "ancient" device, perfectly interpreting the true meaning of "the realm from far away is always in the song, and the material contains magic and can always be found".

The first unit to complete the above research results is Jilin University, With Associate Professor Yang Kaifeng as the first author and Professor Liu Hongwu as the sole corresponding author. This work has been funded by the National and Jilin Provincial Natural Science Foundation.

China Jilin Network Jike APP reporter Yin Wei

Image courtesy of Jilin University