Fermionic Hubbard model with Rashba or Dresselhaus spin–orbit coupling

Abstract

In this work, we investigate the possible dramatic effects of Rashba or Dresselhaus spin-orbit coupling (SOC) on the fermionic Hubbard model in a two-dimensional square lattice. In the strong coupling limit, it leads to the rotated antiferromagnetic Heisenberg model which is a new class of quantum spin model. For a special equivalent class, we identify a new spin-orbital entangled commensurate ground (Y-y) state subject to strong quantum fluctuations at T=0. We evaluate the quantum fluctuations by the spin wave expansion up to order S 1 2 . In some SOC parameter regimes, the Y-y state supports a massive relativistic incommensurate magnon (C-IC) with its two gap minima positions continuously tuned by the SOC parameters. The C-IC magnons dominate all the low temperature thermodynamic quantities and also lead to the separation of the peak positions between the longitudinal and the transverse spin structure factors. In the weak coupling limit, any weak repulsive interaction also leads to a weak Y-y state. There is only a crossover from the weak to the strong coupling. High temperature expansions of the specific heats in both weak and strong coupling are presented. The dramatic roles to be played by these C-IC magnons at generic SOC parameters or under various external probes are hinted at. Experimental applications to both layered noncentrosymmetric materials and cold atoms are discussed.

Halogen in materials design: Revealing the nature of hydrogen bonding and other non-covalent interactions in the polymorphic transformations of methylammonium lead tribromide perovskite

“…Despite the different functionals used, the conclusions reached for the nature of the intermolecular interactions in o-MAPbBr 3 (as well as those for the other room temperature polymorphs discussed below) and characterized with QTAIM remain the same. Indirect to direct (or direct to indirect) bandgap transition in Pb-based perovskite solar cell materials[101][102][103][104][105] is a consequence of the Rashba-Dresselhaus effect[106], irrespective of whether the material in question is MAPbBr 3 or MAPbI 3 . The effect is related to the splitting of conduction and valence band energy levels in momentum space[106].…”

Quantum incommensurate skyrmion crystals and commensurate to in-commensurate transitions in cold atoms and materials with spin–orbit couplings in a Zeeman field

“…Obviously, due to the lacking of the spin SU(2) symmetry in equation (1), applying the Zeeman field along the two transverse directions H x and H z lead to quite different phenomena and will be presented in separate publications [34]. Rotated anti-ferromagnetic Heisenberg model (RAFMH) will show quite different behaviors [27] (see footnote 7) and will also be presented in separate publications.…”

“…However, the AFM is for spin = can be compensated by increasing the atom number N per site. Unfortunately, the RAFHM may not share such a nice properties [27](see footnote 7). So in the aspect of temperature requirements, it would be easier to study the IC-SkX correlations in figures 1 and 2 than to study the AFM correlations [27] (see footnote 7).…”

Topological spin textures in chiral magnets on the honeycomb lattice with magnetic fields

“…The most mechanism of skyrmion formation is the competition between Dzyaloshinskii-Moriya (DM) interaction [3,4] and ferromagnetic exchange interaction with an external field. The DM interaction arises from the relativistic spin-orbit coupling (SOC) in the presence of broken inversion symmetry, such as in chiral magnets (MnSi, FeGe, Fe 1−x Co x Si, Cu 2 OSeO 3 , etc) [5][6][7][8][9][10][11][12], the metallic ferromagnet/paramagnet bilayers or bulks with artificial DM interaction [13][14][15][16][17], ultra-cold systems with synthetic SOC [18][19][20][21][22][23][24][25][26], which have been researched extensively theoretically and experimentally.…”