Pressure-induced transition from a Mott insulator to a ferromagnetic Weyl metal in La2O3Fe2Se2

Abstract

The insulator-metal transition in Mott insulators, known as the Mott transition, is usually accompanied with various novel quantum phenomena, such as unconventional superconductivity, non-Fermi liquid behavior and colossal magnetoresistance. Here, based on high-pressure electrical transport and XRD measurements, and first-principles calculations, we find that a unique pressure-induced Mott transition from an antiferromagnetic Mott insulator to a ferromagnetic Weyl metal in the iron oxychalcogenide La2O3Fe2Se2 occurs around 37 GPa without structural phase transition. Our theoretical calculations reveal that such an insulator-metal transition is mainly due to the enlarged bandwidth and diminishing of electron correlation at high pressure, fitting well with the experimental data. Moreover, the high-pressure ferromagnetic Weyl metallic phase possesses attractive electronic band structures with six pairs of Weyl points close to the Fermi level, and its topological property can be easily manipulated by the magnetic field. The emergence of Weyl fermions in La2O3Fe2Se2 at high pressure may bridge the gap between nontrivial band topology and Mott insulating states. Our findings not only realize ferromagnetic Weyl fermions associated with the Mott transition, but also suggest pressure as an effective controlling parameter to tune the emergent phenomena in correlated electron systems.

Exploring the Interplay between Structure and Electronic Behavior across Pressure-Induced Isostructural and Structural Transitions in Weyl-Type Semimetal NbAs

“…The broken inversion symmetry is crucial for the existence of the Weyl semimetal phase, which in contrast preserves time-reversal symmetry [14,15]. It is known that exotic phase transitions in materials can be induced through the application of pressure, potentially leading to the emergence of new electronic or magnetic quantum phases [16][17][18][19][20][21][22][23][24][25]. In NbAs, theoretical calculations predicted a sequence of pressure-induced structural transitions from tetragonal-to-hexagonal (another topological phase with different Weyl node geometry) and subsequently the transition from monoclinic to cubic as follows: I4 1 md → P6m2 → P2 1 /c → Pm3m [26].…”

Pressure tuning of superconductivity in TiN thin films

“…Pressure, as a fundamental thermodynamic variable, can modulate the physical properties of materials, providing a new dimension of research in condensed matter physics [1,2]. The characteristics of materials under high pressure are remarkably different from those observed at ambient conditions, and many novel physical phenomena emerge under high pressure [3][4][5][6][7][8][9][10]. Moreover, as a clean method to tune the electronic properties without introducing any impurities, high pressure has incomparable advantages in physical property modulation.…”