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PhD Thesis Presentation
Strain Effect in C-paired Spin-Valley Locking Dirac Systems
Speaker Mr. Zhenqiao HUANG
Department of Physics, The Hong Kong University of Science and Technology
Date 26 June 2024 (Wednesday)
Time 4:00 pm
Venue Room 5501 (Lifts 25-26), 5/F Academic Building, HKUST
ABSTRACT

Mechanical strain has long served as a fundamental technique for modulating the physical properties of materials. In magnetic materials, strain not only adjusts magnetic properties but also alters their electronic structures. Owing to the rapid development of antiferromagnetic materials, the emergence of altermagnets and C-paired spin-valley locking (SVL) systems introduces novel prospects in the realms of spintronics and valleytronics within magnetic systems. The strong coupling among the three degrees of freedom, charge, spin, and valley, grants strain modulation versatile in the antiferromagnetic materials. In this thesis, we investigate the effects of both uniform and non-uniform strain in two-dimensional Dirac semimetals with C-paired SVL. First, we explore the piezomagnetic effect induced by uniaxial uniform strain in antiferromagnetic Dirac materials with C-paired SVL. Employing a combination of low-energy effective k · p models and density functional theory (DFT) methods, we predict the emergence of a unconventional piezomagnetic effect in two-dimensional Fe2S materials, and discuss the observed quantum phase transitions. Additionally, we study the pseudo-Landau levels generated by non-uniform strain in these Dirac systems. Based on symmetry analysis and a tight-binding model, we find that straininduced pseudomagnetic fields in such systems can produce Landau levels similar to those under a real magnetic field. We propose that these pseudo-Landau levels can lead to novel transport properties, notably quantized Hall conductivity even without an external magnetic field. Our research enhances the understanding of strain-induced phenomena in advanced magnetic materials and their prospective applications. 

DEPARTMENT OF PHYSICS