Quantum decoherence by magnetic fluctuations in a magnetic topological insulator

Abstract

In magnetic topological insulators, spontaneous time-reversal symmetry breaking by intrinsic magnetic order can gap the topological surface spectrum, resulting in exotic properties like axion electrodynamics, the quantum anomalous Hall effect, and other topological magnetoelectric responses. Understanding the magnetic order and its coupling to topological states is essential to harness these properties. Here, we leverage near-resonant magnetic dipole optical second harmonic generation to probe magnetic fluctuations in the candidate axion insulator EuSn${}_2$(As,P)${}_2$ across its antiferromagnetic phase boundary. We observe a pronounced dimensional crossover in the quantum decoherence induced by magnetic fluctuations, whereby two-dimensional in-plane ferromagnetic correlations at high temperatures give way to three-dimensional long-range order at the Néel temperature. We also observe the breaking of rotational symmetry within the long-range-ordered antiferromagnetic state and map out the resulting spatial domain structure. More generally, we demonstrate the unique capabilities of nonlinear optical spectroscopy to study quantum coherence and fluctuations in magnetic quantum materials.

References in corpus (23)

• Experimental Observation of the Quantum Anomalous Hall Effect in a Magnetic Topological Insulator
• Quantized Anomalous Hall Effect in Magnetic Topological Insulators
• Magnetoelectric polarizability and axion electrodynamics in crystalline insulators
• Topological axion states in magnetic insulator MnBi${}_2$Te${}_4$ with the quantized magnetoelectric effect
• Quantum Anomalous Hall Effect in Hg${}_{1-y}$Mn${}_y$Te Quantum Wells
• Antiferromagnetic topological insulators
• Chiral Topological Superconductor From the Quantum Hall State
• Dynamical Axion Field in Topological Magnetic Insulators
• Higher-order Topology of Axion Insulator EuIn${}_2$As${}_2$
• Axion Electrodynamics in Topological Materials
• Spin fluctuation induced Weyl semimetal state in the paramagnetic phase of EuCd${}_2$As${}_2$
• An ideal Weyl semimetal induced by magnetic exchange
• A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal Cd${}_2$Re${}_2$O${}_7$
• Coupling of magnetic order and charge transport in the candidate Dirac semimetal EuCd${}_2$As${}_2$
• Manipulating of magnetism in the topological semimetal EuCd2As2
• In-plane antiferromagnetic moments in axion topological insulator candidate EuIn${}_2$As${}_2$
• Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties
• Topological Hall Effect Driven by Short-Range Magnetic Orders in EuZn${}_2$As${}_2$
• A-type antiferromagnetic order and magnetic phase diagram of the trigonal Eu spin-7/2 triangular-lattice compound EuSn2As2
• Electric quadrupole second harmonic generation revealing dual magnetic orders in a magnetic Weyl semimetal
• Various magnetism of the compressed antiferromagnetic topological insulator EuSn2As2
• Direct visualization and control of antiferromagnetic domains and spin reorientation in a parent cuprate
• Ultrafast spin dynamics in the proximate quantum spin liquid α-RuCl3