Evidence of an odd-parity hidden order in a strongly spin-orbit coupled correlated iridate Contents: S1. RA-SHG data for Sin-Pout and Sin-Sout geometries above and below TΩ show that the crystal structure of Sr2IrO4 belongs to the centrosymmetric tetragonal 4/m point group as opposed to the previously accepted 4/mmm point group 4,5 . Given the presence of inversion symmetry, the leading order contribution to SHG is the non-local term of electricquadrupole type, which can be expressed as an effective nonlinear polarization aswhere is the electric-quadrupole susceptibility tensor. By enforcing 4/m point group symmetry, is reduced to having 21 non-zero independent elements 6 :With the four additional constraints from degenerate SHG { = , = , = , = }, the number of non-zero independent tensor elements is further reduced to 17. The rotation of the crystal by an angle φ about the c-axis is carried out mathematically by applying a basis transformation on the reduced tensor from the original (primed) to rotated (unprimed) reference frame usingwhere ( ) is the rotation matrix about the c-axis. Finally, the expression that is used to fit theA is a constant determined by the experimental geometry, ( ) is the intensity of the incident 4 beam and ̂ is the polarization of the incoming or outgoing light, which we select to be either linearly P or S polarized. We note that previous work has already shown that there is no evidence of a surface electric-dipole contribution SHG 3 and that the crystallographic symmetry of the surface remains unchanged across TΩ 7 .ii) Fitting RA-SHG data for T < TThe low temperature RA-SHG data are fit to a coherent sum of the electric-quadrupole term described above and a hidden order induced electric-dipole term. The electric-dipole contribution is expressed as a nonlinear polarization (2 ) ∝ ( ) ( ). By enforcing 2/m magnetic point group symmetry, is reduced to having 14 non-zero independent elements:We only discuss the results using a 2/m magnetic point group here although the same procedure was applied to all of the magnetic point groups we surveyed. The additional constraints from degenerate SHG { = , = , = , = } leaves 10 non-zero independent tensor elements remaining. A basis transformation was then carried out on using ( ) = ′ ′ ′ ′ ′ ′ and the expression used to fit the RA-SHG data at Invariance of the magnetic structure under the elements of 2/m1 is explicitly shown in Figs S2 b-e. We note that the 2/m1 magnetic point group assignment does not rely on the magnitude of the magnetic moments on the two structural sub-lattices being equal, even though experimentally they are found to be so. S4. Loop-current order in cuprates versus iridatesLoop-current ordered phases were initially proposed in a three-band CuO2 model of the copperoxide planes where the charge currents are emergent complex hopping terms between oxygen and copper sites 8,9 . In this section, we examine how this model would be modified for Sr2IrO4.Our intention is not to elaborate on any of the details of loop-curr...
aerosols, carbon, emissions, FIRE BEAR Project, fire regimes, forest fire behavior, Scotch pine, Siberia,
A microscopic model of indirect exchange interaction between transition metal impurities in dilute magnetic semiconductors (DMS) is proposed. The hybridization of the impurity delectrons with the heavy hole band states is largely responsible for the transfer of electrons between the impurities, whereas Hund rule for the electron occupation of the impurity d-shells makes the transfer spin selective. The model is applied to such systems as n−type GaN:Mn and p−type (Ga,Mn)As, p−type (Ga,Mn)P. In n−type DMS with Mn 2+/3+ impurities the exchange mechanisms is rather close to the kinematic exchange proposed by Zener for mixed-valence Mn ions. In p−type DMS ferromagnetism is governed by the kinematic mechanism involving the kinetic energy gain of heavy hole carriers caused by their hybridization with 3d electrons of Mn 2+ impurities. Using the molecular field approximation the Curie temperatures T C are calculated for several systems as functions of the impurity and hole concentrations. Comparison with the available experimental data shows a good agreement.
Forest fires resulting from long periods of drought cause extensive forest ecosystem destruction and can impact on the carbon balance and air quality and feed back to the climate system, regionally and globally. Past fire frequency is reconstructed for Tuvan Scots pine stands using dendrochronology and statistics. Central Tuvan Scots pine (Pinus sylvestris) stands are subject to annual fire regimes; however high intensity fires are rare but they are responsible for most of the damage. Low, medium, and high severity fires have shaped the multi-story Scots pine communities, locally and regionally. Fire type and frequency are directly related to weather and climate and are also dependent on anthropogenic influences. The primary dry period, which promotes fire ignition and spread, in Tuva occurs in April and May. In some years, the precipitation deficit combined with high air temperatures induces long periods of drought. Unlike the typical surface fire regime, forest fires that burn during these extreme droughts often become crown fires that result in substantial forest damage and carbon release. The mean fire interval (MFI) is found to be 10.4 years in Balgazyn stands, and the landscape-scale MFI is 22.4 years. High severity, stand-replacing crown fires have a longer MFI. The warmer and dryer weather that is predicted by global climate models is evident in Tuva, and we believe that these changes in weather and climate have resulted in increased fire intensity and severity, rather than fire frequency in the Tuvan region.
An energy level diagram is constructed on the basis of a microscopic Hamiltonian proposed for a description of interacting manganese impurities in diluted magnetic semiconductors (DMS). It is shown that ferromagnetism in p-type III-V DMS is governed by the strong hybridization of Mn 2+ -electrons with the mobile holes and localized states near the top of the valence band. The Curie temperature estimated from the proposed kinematic exchange agrees with the experiments on GaAs : Mn. The model is also applicable to the GaP : Mn system.
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