2D and quasi-2D quantum and magnetic systems
Abstract
This theoretical/computational research will address two classes of materials:1.Single-layer magnets with anomalous transport and topological properties. In recent years, a lot of attention was paid to single layer ferromagnets such as CrI3 or Cr2Ge2Te6. On the contrary, antiferromagnetic single layers, such as MnP(S,Se)3, while relatively intensively researched, have not attracted as much effort as ferromagnets, because so far spintronics has been largely employing ferromagnetic properties, such as anomalous Hall effect,magnetooptics, GMR or spin-splitting. At the same time ferromagnetic devices have an unavoidable problem of stray fields. Very recently, two new classes of magnetic materials have been proposed, dubbed alter-magnets, and Luttinger-compensated ferromagnets. These have most of the beneficial properties of ferromagnets, but do not have stray fields, thus very promising for spintronics. So far nomonolayer materials in either class have been identified, but I have some rather encouraging preliminary results, which I would like to pursue. We will identify several good candidates, which can be grown experimentally and built into devices. 2.Interplay of strong correlations, itineracy and dimensionality. One of the big hits in the last year or so were several reports from different groupsof anomalous properties of bilayers of the hex-agonal (1H-TaSe2) and tetrahedral (1T-TaSe2) monolayers. The former is a good metal (also showing signatures of Ising superconductivity) and the latter a Mott-insulator. Experiments revealed appearance in tunneling of a density of state peak at or near the Fermi surface. It was interpreted as a Kondo peak arising from screening strongly correlated S=1/2 electrons in the 1T layer by itinerant electrons in 1H. These papers were published in the highest-profile journals. Our preliminary calculations indicate substantial, and strongly separation-dependent charge transfer from 1T to 1H. As a result, the Mott insulator becomes strongly self-doped and a peak emulating a Kondo peak appears within the 1T layer, but for entirely different physical reasons. Model calculations based on our DFT parameters, including the charge transfer, indicate the key physics, including Kondo-like screening, occurs entirely in the strongly correlated layer, the heterostructure just playing the role of a charge reservoir.The results are in excellent agreement with STM, indicating that these high-profile experiments are totally misinterpreted! These results suggest that there is a lot of largely unexplored physics there. For instance, nearest neighbor Coulomb repulsion, usually neglected, starts playing a pivotal role at small dopings. It is not impossible that unconventional superconductivity can emerge at shorter interlayer separations, which can be achieved, for instance, by the #nano-squeegeeing# technique developed at NRL. The plan isto venture deeper into this so far unexplored area.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2023
- Source ID
- N000142312480
Entities
People
- Igor I. Mazin
Organizations
- George Mason University
- Office of Naval Research
- United States Navy