The breakdown of both strange metal and superconducting states at a pressure-induced quantum critical point in iron-pnictide superconductors

TL;DR

This study observes the simultaneous breakdown of the strange metal state and superconductivity at a pressure-induced quantum critical point in an iron-pnictide superconductor, revealing a fundamental link between these phenomena.

Contribution

It provides the first evidence of a quantum critical point where both strange metal behavior and superconductivity vanish concurrently under pressure in an iron-pnictide superconductor.

Findings

Resistivity exponent changes from 1 to 2 with pressure.

At 12.5 GPa, the coefficient A and Tc both go to zero.

A and Tc are positively correlated, similar to other unconventional superconductors.

Abstract

The strange metal (SM) state, characterized by a linear-in-temperature resistivity, is often seen in the normal state of high temperature superconductors. It is believed that the SM state is one of the keys to understand the underlying mechanism of high-Tc superconductivity. Here we report the first observation of the concurrent breakdown of the SM normal state and superconductivity at a pressure-induced quantum critical point in an iron-pnictide superconductor, Ca10(Pt4As8)((Fe0.97Pt0.03)2As2)5. We find that, upon suppressing the superconducting state by applying pressure, the power exponent changes from 1 to 2, and the corresponding coefficient A, the slope of the temperature-linear resistivity per FeAs layer, gradually diminishes. At a critical pressure (12.5 GPa), A and Tc go to zero concurrently,where a quantum phase transition (QPT) from a superconducting state with a SM normal state to a non-superconducting Fermi liquid state takes place. Scaling analysis on the results obtained from the pressurized 1048 superconductor reveals that A and Tc have a positive relation, which exhibits a similarity with that is seen in other chemically-doped unconventional superconductors, regardless of the type of the tuning method (doping or pressurizing), the crystal structure, the bulk or film superconductors and the nature of dopant. These results suggest that there is a simple but powerful organizational principle of connecting the SM normal state with the high-Tc superconductivity.