D-instanton Effects on the Holographic Weyl Semimetals

Abstract

We investigate D-insatnton effects on the holographic Weyl semimetal in top-down approach. From the free energy of the D7 brane embedding solutions, we get phase diagram in terms of the electron mass, instanton number, and temperature in the unit of the weyl parameter. We calculate non-linear conductivities from the regularity condition of the probe D7 brane and investgate anomalous Hall phenomena in the boundary system. From the study of the phase diagram, we suggest the gaped phase induced by the instanton to a topological insulator.

Figures (9)

• Figure 1: D7 brane embeddings without $q$ (a), (b) and without $b$ (c), (d). Here, we set $\xi_h=1$ which shown as a black disc.
• Figure 2: $m_e$ dependence of D7 brane embeddings for (a) $q/b=1$, (b) $q/b=7$. The blue lines denote the Minkowski embedding and the orange line to black hole embedding. Here, we set $\xi_h=1$ which shown as a black disc.
• Figure 3: $m_e$ dependence of the free energy density $f$ for (a) $q/b=1$, (c) $q/b=7$. Three embeddings for the critical $m_e$ (vertical dashed lines) are plotted for (b) $q/b=1$, (d) $q/b=7$, respectively.
• Figure 4: phase diagram surface in $\left( m, T, q\right)$ for a nonzero $b$. Right figure is detailed phase diagram near origin of the left phase diagram.
• Figure 5: $b$ dependence of phase transition temperature at $m_e/b=0$.