152 research outputs found
Skyrmions and Hall viscosity
We discuss the contribution of magnetic Skyrmions to the Hall viscosity and
propose a simple way to identify it in experiments. The topological Skyrmion
charge density has a distinct signature in the electric Hall conductivity that
is identified in existing experimental data. In an electrically neutral system,
the Skyrmion charge density is directly related to the thermal Hall
conductivity. These results are direct consequences of the field theory Ward
identities, which relate various physical quantities based on symmetries and
have been previously applied to quantum Hall systems.Comment: 10 pages, based on the invited talk at the 62nd Annual Conference on
Magnetism and Magnetic Materials (MMM conference), November 6-10, Pittsburgh,
P
Entanglement Entropy with Background Gauge Fields
We study the entanglement entropy, the R\'enyi entropy, and the mutual
(R\'enyi) information of Dirac fermions on a 2 dimensional torus in the
presence of constant gauge fields. We derive their general formulas using the
equivalence between twisted boundary conditions and the background gauge
fields. Novel and interesting physical consequences have been presented in
arXiv:1705.01859. Here we provide detailed computations of the entropies and
mutual information in a low temperature limit, a large radius limit, and a high
temperature limit. The high temperature limit reveals rather different physical
properties compared to those of the low temperature one: there exist two
non-trivial limits that depend on a modulus parameter and are not smoothly
connected.Comment: 37 pages, v2: some formulas in section 4.3 are correcte
Skyrmions and Hall Transport
We derive a generalized set of Ward identities that captures the effects of
topological charge on Hall transport. The Ward identities follow from the 2+1
dimensional momentum algebra, which includes a central extension proportional
to the topological charge density. In the presence of topological objects like
Skyrmions, we observe that the central term leads to a direct relation between
the thermal Hall conductivity and the topological charge density. We extend
this relation to incorporate the effects of a magnetic field and an electric
current. The topological charge density produces a distinct signature in the
electric Hall conductivity, which is identified in existing experimental data,
and yields further novel predictions. For insulating materials with translation
invariance, the Hall viscosity can be directly determined from the Skyrmion
density and the thermal Hall conductivity to be measured as a function of
momentum.Comment: 6+1 pages including Supplemental Material. Version to appear in
Physical Review Letter
Generalizing Thiele Equation
We generalize the Thiele equation with a transverse velocity to the skyrmion
motion described by the collective coordinate of magnetization vector. It is
applied to investigate significant disparity in the existing data sets of
skyrmion and antiskyrmion Hall angles. Our analysis further reveals interesting
differences of these Hall angles near the angular momentum compensation point.
We identify a possible physical quantity that is responsible for the disparity.Comment: 6 pages, 3 figures, published versio
Holographic Renormalization of Einstein-Maxwell-Dilaton Theories
We generalize the boundary value problem with a mixed boundary condition that involves the gauge and scalar fields in the context of Einstein-Maxwell-Dilaton theories. In particular, the expectation value of the dual scalar operator can be a function of the expectation value of the current operator. The properties are prevalent in a fixed charge ensemble because the conserved charge is shared by both fields through the dilaton coupling, which is also responsible for non-Fermi liquid properties. We study the on-shell action and the stress energy tensor to note practical importances of the boundary value problem. In the presence of the scalar fields, physical quantities are not fully fixed due to the finite boundary terms that manifest in the massless scalar or the scalar with mass saturating the Breitenlohner-Freedman bound
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