arXiv subjects

Muting Xie

Publications and source records attributed to Muting Xie.

5 recordsLinked to original sources

arXiv2025

Hidden integer quantum ferroelectricity in chiral Tellurium

Ferroelectricity is a cornerstone of functional materials research, enabling diverse technologies from non-volatile memory to optoelectronics. Recently, type-I integer quantum ferroelectricity (IQFE), unconstrained by symmetry, has been proposed and experimentally demonstrated; however, as it arises from ionic displacements of an integer lattice vector, the initial and final states are macroscopically indistinguishable, rendering the physical properties unchanged. Here, we propose for the first time the nontrivial counterpart (i.e., type-II IQFE) where the polarization difference between the initial and final states is quantized but the macroscopical properties differ. We further demonstrate the existence of type-II IQFE in bulk chiral tellurium. In few-layer tellurium, the total polarization remains nearly quantized, composed of a bulk-inherited quantum component and a small surface-induced contribution. Molecular dynamics simulations reveal surface-initiated, layer-by-layer switching driven by reduced energy barriers, explaining why ferroelectricity was observed experimentally in few-layer tellurium, but not in bulk tellurium yet. Interestingly, the chirality of the initial and final states in bulk tellurium is opposite, suggesting a novel way to control structural chirality with electric field in chiral photonics and nonvolatile ferroelectric memory devices.

cond-mat.mtrl-sci↗

arXiv2025

Defect-Charge-Driven 90{\deg} Switching in HfO2

Hafnium dioxide (HfO2) is a CMOS-compatible ferroelectric showing both 180{\deg} and 90{\deg} switching, yet the microscopic nature of the 90{\deg} pathway remains unresolved. We show that the 90{\deg} rotation pathway, negligible in pristine HfO2, becomes dominant under E// [111] when induced by charged oxygen vacancies. This pathway is more fatigue-resistant than the 180{\deg} reversal pathway, while delivering the same polarization change along [111] (2Pr=60 {\mu}C/cm^2 ). This charge-driven switching arises from two factors: the crystal geometry of HfO2 and the intrinsic nature of rotational pathways, the latter suggesting a possible general tendency for defect charge to bias rotation over reversal in ferroelectrics. Together these findings reveal a pathway-level origin of fatigue resistance and establish defect charge as a general control parameter for polarization dynamics.

cond-mat.mtrl-sci↗

arXiv2024

Role of Domain Walls on Imprint and Fatigue in HfO2-Based Ferroelectrics

HfO2-based ferroelectric materials are promising for the next generation of memory devices, attracting significant attention. However, their potential applications are significantly limited by fatigue and imprint phenomena, which affect device lifetime and memory capabilities. Here, to accurately describe the dynamics and field effects of HfO2, we adopt our newly developed DREAM-Allegro network scheme and develop a comprehensive machine-learning model for HfO2. Such model can not only predict the interatomic potential, but also predict Born effective charges. Applying such model, we explore the role of domain dynamics in HfO2 and find that the fatigue and imprint phenomena are closely related to the so-called E-path and T-path switching pathways. Based on the different atomic motions in the two paths, we propose that an inclined electric field can sufficiently suppress fatigue and enhancing the performance of HfO2-based ferroelectric devices.

cond-mat.mtrl-sci↗

arXiv2024

Switchable Ferroelectricity in Subnano Silicon Thin Films

Recent advancements underscore the critical need to develop ferroelectric materials compatible with silicon. We systematically explore possible ferroelectric silicon quantum films and discover a low-energy variant (hex-OR-2*2-P) with energy just 1 meV/atom above the ground state (hex-OR-2*2). Both hex-OR-2*2 and hex-OR-2*2-P are confirmed to be dynamically and mechanically stable semiconductors with indirect gaps of 1.323 eV and 1.311 eV, respectively. The ferroelectric hex-OR-2*2-P exhibits remarkable in-plane spontaneous polarization up to 120 Pc/m and is protected by a potential barrier (13.33 meV/atom) from spontaneously transitioning to hex-OR-22. To simulate the switching ferroelectricity in electric fields of the single-element silicon bilayer, we develop a method that simultaneously learns interatomic potentials and Born effective charges (BEC) in a single equivariant model with a physically informed loss. Our method demonstrates good performance on several ferroelectrics. Simulations of hex-OR-2*2-P silicon suggest a depolarization temperature of approximately 300 K and a coercive field of about 0.05 V/{\AA}. These results indicate that silicon-based ferroelectric devices are feasible, and the ground state phase of the silicon bilayer (hex-OR-2*2) is an ideal system. Our findings highlight the promise of pure silicon ferroelectric materials for future experimental synthesis and applications in memory devices, sensors, and energy converters.

cond-mat.mtrl-sci↗

arXiv2023

Topological interfacial states in ferroelectric domain walls of two-dimensional bismuth

Using machine learning methods, we explore different types of domain walls in the recently unveiled single-element ferroelectric, the bismuth monolayer [Nature 617, 67 (2023)]. Remarkably, our investigation reveals that the charged domain wall configuration exhibits lower energy compared to the uncharged domain wall structure. We also demonstrate that the experimentally discovered tail-to-tail domain wall maintains topological interfacial states caused by the change in the Z_2 number between ferroelectric and paraelectric states. Interestingly, due to the intrinsic built-in electric fields in asymmetry DW configurations, we find that the energy of topological interfacial states splits, resulting in an accidental band crossing at the Fermi level. Our study suggests that domain walls in two-dimensional bismuth hold potential as a promising platform for the development of ferroelectric domain wall devices.

cond-mat.mtrl-sci↗