Abnormal T-linear susceptibility and Phase diagram of BaFe$_{2-x}$Co$_x$As$_2$ single crystals

TL;DR

This study investigates the phase diagram of BaFe$_{2-x}$Co$_x$As$_2$ single crystals, revealing unusual T-linear susceptibility, coexistence of SDW and superconductivity, and a transition from non-Fermi-liquid to Fermi-liquid behavior with doping.

Contribution

It provides a detailed electronic phase diagram of BaFe$_{2-x}$Co$_x$As$_2$, highlighting the coexistence of SDW and superconductivity and the unusual T-linear susceptibility behavior.

Findings

SDW transition observed in resistivity and susceptibility

Unusual T-linear susceptibility persists up to 700 K

Coexistence of SDW and superconductivity around x=0.17

Abstract

We study systematically transport, susceptibility and heat capacity for BaFe$_{2-x}$Co$_x$As$_2$ single crystals. In the underdoped region, spin density wave (SDW) transition is observed in both resistivity and susceptibility. The magnetic susceptibility shows unusual T-linear dependence above SDW transition up to 700 K. With Co doping, SDW ordering is gradually suppressed and superconductivity emerges with a dome-like shape. Electrical transport, specific heat and magnetic susceptibility indicate that SDW and superconductivity coexist in the sample BaFe$_{2-x}$Co$_x$As$_2$ around x = 0.17, being similar with (Ba,K)Fe$_2$As$_2$. When x$>$0.34, the superconductivity completely disappears. A crossover from non-Fermi-liquid state to Fermi-liquid state is observed with increasing Co doping. A detailed electronic phase diagram about evolution from SDW to superconducting state is given.