[Paper Review] Discovery of a metallic room-temperature d-wave altermagnet KV2Se2O

Bei Jiang, Mingzhe Hu+20 more|arXiv (Cornell University)|Aug 1, 2024

Magnetism in coordination complexes4 citations

TL;DR

This paper reports the discovery of a metallic, room-temperature d-wave altermagnet, KV2Se2O, exhibiting time-reversal symmetry breaking and spin-split band structures with zero net magnetization. Through comprehensive electronic and magnetic characterization, the study identifies highly anisotropic spin-polarized Fermi surfaces and spin-density-wave order, establishing it as a robust platform for spintronics and many-body physics with d-wave spin-momentum locking.

ABSTRACT

Beyond conventional ferromagnetism and antiferromagnetism, altermagnetism is a recently discovered unconventional magnetic phase characterized by time-reversal symmetry breaking and spin-split band structures in materials with zero net magnetization. This distinct magnetic phase not only enriches the understanding of fundamental physical concepts but also has profound impacts on condense-matter physics research and practical device applications. Spin-polarized band structures have been recently observed in semiconductors MnTe and MnTe2 with vanishing net magnetization, confirming the existence of this unconventional magnetic order. Metallic altermagnets have unique advantages for exploring novel physical phenomena related to low-energy quasiparticle excitations and for applications in spintronics as electrical conductivity in metals allows the direct manipulation of spin current through electric field. Here, through comprehensive characterization and analysis of the magnetic and electronic structures of KV2Se2O, we have unambiguously demonstrated a metallic room-temperature altermaget with d-wave spin-momentum locking. The highly anisotropic spin-polarized Fermi surfaces and the spin-density-wave order emerging in the altermagnetic phase make it an extraordinary platform for designing high-performance spintronic devices and studying many-body effects coupled with the unconventional magnetism.

Motivation & Objective

• To identify and characterize a new class of metallic altermagnets with unconventional spin textures at room temperature.
• To investigate the electronic structure and magnetic order in KV2Se2O to confirm altermagnetic behavior with d-wave spin-momentum locking.
• To explore the potential of metallic altermagnets in enabling low-energy quasiparticle excitations and spintronic device applications.
• To establish KV2Se2O as a platform for studying many-body effects coupled with unconventional magnetism.

Proposed method

• Conducting angle-resolved photoemission spectroscopy (ARPES) to map the spin-polarized Fermi surface and band structure of KV2Se2O.
• Performing first-principles density functional theory (DFT) calculations to model the electronic and magnetic properties.
• Analyzing the spin texture and spin-momentum locking using symmetry and band structure analysis.
• Measuring electrical transport and magnetic response to confirm metallic behavior and altermagnetic order.
• Evaluating spin-density-wave (SDW) order through analysis of Fermi surface nesting and spin splitting.
• Comparing experimental data with theoretical predictions to confirm d-wave symmetry in spin-momentum locking.

Experimental results

Research questions

• RQ1 Does KV2Se2O host a metallic altermagnetic phase with time-reversal symmetry breaking and zero net magnetization at room temperature?
• RQ2 What is the nature of spin-momentum locking in KV2Se2O, and does it exhibit d-wave symmetry?
• RQ3 How do the spin-polarized Fermi surfaces and spin-density-wave order influence its electronic and transport properties?
• RQ4 To what extent does the altermagnetic order in KV2Se2O support novel many-body effects and low-energy quasiparticle excitations?
• RQ5 Can KV2Se2O serve as a viable platform for spintronic devices due to its metallic conductivity and robust spin texture?

Key findings

• KV2Se2O exhibits a metallic, room-temperature altermagnetic phase with time-reversal symmetry breaking and zero net magnetization.
• The material displays d-wave spin-momentum locking, confirmed by spin-polarized Fermi surface measurements and symmetry analysis.
• Highly anisotropic spin-polarized Fermi surfaces are observed, indicating strong spin-orbit coupling and unconventional spin texture.
• Spin-density-wave order emerges in the altermagnetic phase, driven by Fermi surface nesting and spin splitting.
• First-principles calculations confirm the stability of the altermagnetic ground state and the d-wave nature of spin-momentum locking.
• The combination of metallic conductivity and robust spin-polarized bands positions KV2Se2O as a promising candidate for spintronic applications and many-body physics studies.