Pressure induced antiferromagnetic-tetragonal to nonmagnetic-collapse-tetragonal insulator-metal transition in ThMnAsN

TL;DR

This study uses first principles calculations to reveal a pressure-induced transition in ThMnAsN from a magnetic tetragonal phase to a nonmagnetic collapsed tetragonal phase, accompanied by insulator-metal and structural changes.

Contribution

It is the first to identify and characterize the pressure-driven magneto-structural and electronic phase transitions in ThMnAsN, including the collapse of Mn magnetic moments and electronic structure evolution.

Findings

Critical pressure for transition ~9 GPa.

Complete collapse of Mn magnetic moments at transition.

Electronic structure resembles Fe-based superconductors at high pressure.

Abstract

We report first principles numerical discovery of hydrostatic pressure driven tetragonal to collapsed tetragonal transition in 1111-type material ThMnAsN accompanied by simultaneous magneto-structural, insulator to metal transition together with complete collapse of Mn moment. We present detailed evolution of various structural parameters, magnetism and electronic structures of ThMnAsN with increasing hydrostatic pressure. All the structural parameters show anomalies at a critical pressure P$_c \sim$ 9 GPa; c-lattice parameter, out of plane As-As bond length, anion height (h$_{As}$) undergo drastic modification compared to the in-plane parameters which is manifested in an iso-structural phase transition from tetragonal to a collapsed tetragonal (cT) phase. These modifications in "local structural correlations" due to pressure destroys usually localized nature of Mn moments and gets completely quenched. Apart from that the elastic constant, the electronic structures also bear the finger prints of insulator-metal and magneto-structural transition at higher pressures accompanying a total collapse of magnetic moment at the vicinity of 9 GPa. The critical value of the pressure P$_c$ at which tetragonal to collapse tetragonal phase transition occurs, remains robust with respect to the on-site Hubbard correlation (U). The dynamical stability of the compound at higher pressures are affirmed through detailed computations of phonon dispersion curves endowed with positive phonon frequency through out the Brillouin zone. The effect of magnetic spin structure on the electronic band structures are obtained through band unfolding. The electronic structure of ThMnAsN at higher pressures "orbital selectively" influences bands, band gap and closely resembles with the electronic structure of Fe-based superconductors with the occurrences of orbital selective Lifshitz transition.