Related papers: Chern-Simons orbital magnetoelectric coupling in g…
The contribution of reducible connections to the U(N) Chern-Simons invariant of a Seifert manifold $M$ can be expressed in some cases in terms of matrix integrals. We show that the U(N) evaluation of the LMO invariant of any rational…
We study complex Chern-Simons theory on a Seifert manifold $M_3$ by embedding it into string theory. We show that complex Chern-Simons theory on $M_3$ is equivalent to a topologically twisted supersymmetric theory and its partition function…
Considerable efforts have recently been devoted to the experimental realization of a two-dimensional Chern insulator, i.e., a system displaying a quantum anomalous Hall effect. However, existing approaches such as those based on magnetic…
The electronic contribution to the magnetically induced polarization in orthorhombic TbMnO3 is studied from first principles. We compare the cases in which the spin cycloid, which induces the electric polarization via the spin-orbit…
The effect of a magnetic field on a two-dimensional Chern band insulator is discussed. It is shown that, unlike the trivial insulator, an anomalous Hall insulator with Chern number $C$ becomes a metal when a magnetic field is applied at…
We formulate a Chern-Simons composite fermion theory for Fractional Chern Insulators (FCIs), whereby bare fermions are mapped into composite fermions coupled to a lattice Chern-Simons gauge theory. We apply this construction to a Chern…
We have found a remarkable increase (up to 60 %) of the dielectric constant with the onset of magnetic order at 42 K in the metastable orthorhombic structures of YMnO3 and HoMnO3 that proves the existence of a strong magneto-dielectric…
Spin-phonon coupling underlies a number of diverse range of phenomena of recent interest, particularly in transition metal insulators with strong spin-orbit effects, where it may give rise to hybrid magnetoelastic excitations, and the…
We consider Chern-Simons theory with complex gauge group and present a complete non-perturbative evaluation of the path integral (the partition function and certain expectation values of Wilson loops) on Seifert fibred 3-Manifolds. We use…
With a combined ab initio density functional and model Hamiltonian approach we establish that in the recently discovered multiferroic phase of the manganite Sr$_{1/2}$Ba$_{1/2}$MnO$_{3}$ the polar distortion of Mn and O ions is stabilized…
We have investigated the dielectric anomalies associated with spin ordering transitions in the tetragonal spinel Mn$_3$O$_4$, using thermodynamic, magnetic, and dielectric measurements. We find that two of the three magnetic ordering…
We have investigated the magnetoelectric coupling in the lone pair containing piezoelectric ferrimagnet Cu2OSeO3. Significant magnetocapacitance develops in the magnetically ordered state (TC = 60 K). We find critical behavior near TC and a…
We propose characterization of the three-dimensional topological insulator by using the Chern number for the entanglement Hamiltonian (entanglement Chern number). Here we take the extensive spin partition of the system, that pulls out the…
In this work we study some physical phenomena that emerge in the vicinity of a magnetoelectric boundary. For simplicity, we restrict to the case of a planar boundary described by a coupling between the gauge field with a planar external…
A key feature of topological insulators is the robustness of the electron energy spectrum. At a surface of a topological insulator, Dirac point is protected by the characteristic symmetry of the system. The breaking of the symmetry opens a…
We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr$_2$GaN. A magnetic phase transition is identified at $T \approx 170$ K, whereas no trace of structural transition is observed down to 6 K.…
We derive a spin-orbital model for insulating LaMnO_3 which fulfills the SU(2) symmetry of S=2 spins at Mn^{3+} ions. It includes the complete e_g and t_{2g} superexchange which follows from a realistic Mn^{2+} multiplet structure in cubic…
The universal perturbative invariants of rational homology spheres can be extracted from the Chern-Simons partition function by combining perturbative and nonperturbative results. We spell out the general procedure to compute these…
Working in the Wannier representation, we derive an expression for the orbital magnetization of a periodic insulator. The magnetization is shown to be comprised of two contributions, an obvious one associated with the internal circulation…
We study three-dimensional {\cal N}=2 U(N) Chern-Simons theory on S^3 coupled to 2N_f chiral multiplets deformed by mass terms. The partition function localizes to a matrix integral, which can be exactly computed in the large N limit. In a…