Chiral magnetic effect at low temperature

TL;DR

This paper studies the chiral magnetic effect at low temperatures using instanton vacuum configurations, revealing how the effect diminishes with increasing temperature and becomes negligible above approximately 300 MeV.

Contribution

It introduces a framework employing instanton fluctuations to analyze the CME at low temperatures, highlighting the temperature dependence of the effect.

Findings

Longitudinal current is much larger than transverse

CME becomes insensitive to magnetic field as temperature increases

Instanton contribution diminishes and becomes negligible above ~300 MeV

Abstract

We investigate the chiral magnetic effect (CME) under a strong magnetic field B = B_0 x_3 at low temperature T < T^chi_c. For this purpose, we employ the instanton vacuum configuration with the finite instanton-number fluctuation Delta, which relates to the nontrivial topological charge Q_t. We compute the vacuum expectation values of the local chiral density <rho_chi>, chiral charge density <n_chi> and induced electromagnetic current <j_mu>, which signal the CME, as functions of T and B_0. We observed that the longitudinal EM current is much larger than the transverse one, |j_perp/j_parallel| ~ Q_t, and the <n_chi> equals to the |<j_{3,4}>|. It also turns out that the CME becomes insensitive to the magnetic field as T increases, according to the decreasing instanton, i.e. tunneling effect. Within our framework, the instanton contribution to the CME becomes almost negligible beyond T~300 MeV.