arXiv subjects

Xiaolan Yan

Publications and source records attributed to Xiaolan Yan.

3 recordsLinked to original sources

arXiv2026

Simplified criteria for identifying and designing altermagnetic crystals in real space

Altermagnetism is a compensated magnetic phase characterized by zero net magnetization and exchange-driven spin splitting. However, identifying altermagnets among collinear antiferromagnets usually requires full magnetic-space-group or spin-group analysis, which is not always intuitive. Here we formulate a simple real-space criterion based on how the crystallographic operations of the host nonmagnetic structure permute the two opposite-spin sublattices. We show that altermagnets usually exist on collinear compensated antiferromagnets whose magnetic primitive cell coincides with the host nonmagnetic crystallographic primitive cell. In this case, altermagnetic spin splitting is generally allowed unless an inversion-type operation exists that exchanges the two opposite-spin sublattices. Using chemically ordered Mn2SSe prototypes derived from zinc-blende or rocksalt parent structures, we demonstrate that these criteria can be easily used to construct the three symmetry classes by controlling chemical ordering and magnetic-sublattice permutation. Similar rules can also be applied to low-dimensional crystals or quasicrystals. Our work reduces the identification of altermagnets to a transparent real-space symmetry test and provides a practical route for designing altermagnetic crystals.

cond-mat.mtrl-sci↗

arXiv2022

Temperature Effect on Charge-state Transition Levels of Defects in Semiconductors

Defects are crucial in determining the overall physical properties of semiconductors. Generally, the charge-state transition level (TEL), one of the key physical quantities that determines the dopability of defects in semiconductors, is temperature dependent. However, little is known about the temperature dependence of TEL, and, as a result, almost all existing defect theories in semiconductors are built on a temperature-independent approximation. In this article, by deriving the basic formulas for temperature-dependent TEL, we have established two fundamental rules for the temperature dependence of TEL in semiconductors. Based on these rules, surprisingly, it is found that the temperature dependences of TEL for different defects are rather diverse: it can become shallower, deeper, or stay unchanged. This defect-specific behavior is mainly determined by the synergistic or opposing effects between free energy corrections (determined by the local volume change around the defect during a charge-state transition) and band edge changes (which differ for different semiconductors). These basic formulas and rules, confirmed by a large number of state-of-the-art temperature-dependent defect calculations in GaN, may potentially be widely adopted as guidelines for understanding or optimizing doping behaviors in semiconductors at finite temperatures.

cond-mat.mtrl-sci↗

arXiv2021

A Unified Theory and Fundamental Rules of Strain-dependent Doping Behaviors in Semiconductors

Enhancing the dopability of semiconductors via strain engineering is critical to improving their functionalities, which is, however, largely hindered by the lack of fundamental rules. In this Letter, for the first time, we develop a unified theory to understand the total energy changes of defects (or dopants) with different charge states under strains, which can exhibit either parabolic or superlinear behaviors, determined by the size of defect-induced local volume change (ΔV). In general, ΔV increases (decreases) when an electron is added (removed) to (from) the defect site. Consequently, in terms of this unified theory, three fundamental rules can be obtained to further understand or predict the diverse strain-dependent doping behaviors, i.e., defect formation energies, charge-state transition levels, and Fermi pinning levels, in semiconductors. These three fundamental rules could be generally applied to improve the doping performance or overcome the doping bottlenecks in various semiconductors.

cond-mat.mtrl-sci↗