Ultrafast Coherent THz Lattice Dynamics Coupled to Spins in the van der Waals Antiferromagnet FePS₃

Abstract

Coherent THz optical lattice and hybridized phonon–magnon modes are triggered by femtosecond laser pulses in the antiferromagnetic van der Waals semiconductor FePS3. The laser‐driven lattice and spin dynamics are investigated in a bulk crystal as well as in a 380 nm‐thick exfoliated flake as a function of the excitation photon energy, sample temperature and applied magnetic field. The pump‐probe magneto‐optical measurements reveal that the amplitude of a coherent phonon mode oscillating at 3.2 THz decreases as the sample is heated up to the Néel temperature. This signal eventually vanishes as the phase transition to the paramagnetic phase occurs, thus revealing its connection to the long‐range magnetic order. In the presence of an external magnetic field, the optically triggered 3.2 THz phonon hybridizes with a magnon mode, which is utilized to excite the hybridized phonon–magnon mode optically. These findings open a pathway toward the optical control of coherent THz photo–magnonic dynamics in a van der Waals antiferromagnet, which can be scaled down to the 2D limit.

Magnetic order in 2D antiferromagnets revealed by spontaneous anisotropic magnetostriction

“…In addition to ferromagnetism, first observed in CrI 3 [2] and Cr 2 Ge 2 Te 6 [3], antiferromagnetism in 2D materials has also been studied in FePS 3 [4] and CrSBr [5]. Antiferromagnetic (AF) materials are of particular technological interest due to their high spin-wave propagation speed and lack of macroscopic stray fields, making them strong candidates for spintronic and magnonic applications [6][7][8][9][10].…”

An antiferromagnetic semiconducting FeCN2monolayer with a large magnetic anisotropy and strong magnetic coupling

“…[12][13][14] Experimentally, 2D FeOCl shows a strong spin-phonon coupling effect below B83.3 K. 15 van der Waals antiferromagnet FePS 3 presents ultrafast coherent THz lattice dynamics coupled to spins. 16 Theoretical calculations also play an important role in designing magnetic materials, 17,18 rationalizing magnetic origins, 19,20 and finding effective routes (e.g., doping, strain engineering, and carrier modulation) to modulate magnetism. [21][22][23] Additionally, the introduction of various AFM orders (including zigzag, Ne ´el, and striped types) also enriches the properties of materials.…”

2D antiferromagnetic semiconducting FeCN with interesting properties

“…11 Recent advances in material synthesis and characterization techniques have facilitated the discovery of 2D AFM semiconductors, such as 2D FeOCl with a strong spinphonon coupling effect below B83.3 K, 12 and van der Waals antiferromagnet FePS 3 with ultrafast coherent THz lattice dynamics coupled to spins. 13 These findings have considerably stimulated the exploration of 2D AFM materials with novel structures and properties.…”

“…19 Iron (Fe), as a typical magnetic element with rich valenceelectron configurations, has shown great potential for stabilizing 2D Fe-based materials. 12,13,[20][21][22][23][24] For example, the 2D Fe 3 GeTe 2 material experiences a transition from ferromagnet to antiferromagnet below 152 K. 20 Distinct from the non-magnetic FeS and FeSe monolayers, the FM FeTe monolayer satisfies the Stoner criterion and has a total magnetization of 3.8 m B per unit cell. 21 The T-phase Fe 2 C monolayer exhibits a room-temperature AFM order.…”