arXiv subjects

Suyang Sun

Publications and source records attributed to Suyang Sun.

7 recordsLinked to original sources

arXiv2026

Melting behavior and dynamical properties of Cr2Ge2Te6 phase-change material

Cr2Ge2Te6 (CrGT) is known as an intrinsic ferromagnetic semiconductor and a promising candidate for phase-change memory applications. In amorphous CrGT, Cr atoms form non-defective octahedral motifs with Te atoms, similar to those in the crystalline phase. The abundance of Cr[Te6] octahedra is regarded as the key structural factor in reducing the resistance drift coefficient of amorphous CrGT. However, the stage at which these octahedra emerge during melt-quench amorphization remains unclear. Here, we present ab initio molecular dynamics (AIMD) simulations to model the melting process of crystalline CrGT and to investigate the dynamical properties of liquid and supercooled liquid CrGT in detail. Upon heating, Ge atoms are observed to leave their lattice sites earlier than Cr and Te atoms, diffusing into the van der Waals gap and initiating the collapse of the layered structure. The Cr[Te6] octahedra are more robust, maintaining their structural pattern up to 1400 K despite continuous rupture and re-formation of Cr-Te bonds. At higher temperatures, Cr and Te atoms start to migrate independently. In supercooled liquid CrGT at 550 K, most Cr-centered octahedra remain intact, with only limited Cr-Te bond breaking. The collective motion of these octahedra in this temperature regime helps explain why crystallization in CrGT devices can be accomplished in tens of nanoseconds.

cond-mat.mtrl-sci↗

arXiv2026

DUAP: Dual-task Universal Adversarial Perturbations Against Voice Control Systems

Modern Voice Control Systems (VCS) rely on the collaboration of Automatic Speech Recognition (ASR) and Speaker Recognition (SR) for secure interaction. However, prior adversarial attacks typically target these tasks in isolation, overlooking the coupled decision pipeline in real-world scenarios. Consequently, single-task attacks often fail to pose a practical threat. To fill this gap, we first utilize gradient analysis to reveal that ASR and SR exhibit no inherent conflicts. Building on this, we propose Dual-task Universal Adversarial Perturbation (DUAP). Specifically, DUAP employs a targeted surrogate objective to effectively disrupt ASR transcription and introduces a Dynamic Normalized Ensemble (DNE) strategy to enhance transferability across diverse SR models. Furthermore, we incorporate psychoacoustic masking to ensure perturbation imperceptibility. Extensive evaluations across five ASR and six SR models demonstrate that DUAP achieves high simultaneous attack success rates and superior imperceptibility, significantly outperforming existing single-task baselines.

cs.CR↗

arXiv2025

Amorphous phase-change memory alloy with no resistance drift

Spontaneous structural relaxation is intrinsic to glassy materials due to their metastable nature. For phase-change materials (PCMs), the resultant temporal change in electrical resistance seriously hamper in-memory computing (IMC) applications. Here, we report an ab-initio-calculation-informed design of amorphous PCM composed of robust "molecule-like" motifs with minimal Peierls distortion, depriving the amorphous alloy of structural ingredients that would gradually evolve upon aging to entail resistance drift. We demonstrate amorphous CrTe3 thin films that display practically no resistance drift at any working temperature from -200 to 165 degree C. We achieve multilevel programming of CrTe3 through both step-wise crystallization and step-wise amorphization using a hybrid opto-electronic device at various temperatures. Moreover, the application potential of CrTe3 in neuromorphic computing is testified by its incorporation in a vehicle with automatic path-tracking function. Our work opens a new avenue to achieving IMC-requisite properties via judicious design of the composition and atomic-level structure of disordered PCM alloys.

cond-mat.mtrl-sci↗

arXiv2025

Spin glass behavior in amorphous CrSiTe3 alloy

Owing to the intrinsically high crystallization temperatures, layered phase-change materials, such as CrGeTe3 and InGeTe3, are attracting attention for embedded memory applications, In addition to the electrical contrast, a major change in magnetic properties is observed in CrGeTe3 upon switching from the crystalline to the amorphous state. In this work, we report a combined ab initio modeling and magnetic characterization study on the isostructural silicon parent compound of CrGeTe3, namely, CrSiTe3. Amorphous CrSiTe3 has similar structural properties to amorphous CrGeTe3; however, it shows a smaller energy difference between the ferromagnetic configuration and the random magnetic configuration, indicating a high probability of spin glass formation. Indeed, direct-current and alternating-current magnetic measurements show that the coercive force of amorphous CrSiTe3 is higher than that of amorphous CrGeTe3. Therefore, the pinning effect of spins is enhanced in amorphous CrSiTe3, leading to a more robust spin glass state with a higher freezing temperature. The large magnetic contrast between the amorphous and crystalline phase could make CrSiTe3 a potential candidate for phase-change magnetic switching applications.

cond-mat.mtrl-sci↗

arXiv2024

Ab initio investigation of layered TMGeTe3 alloys for phase-change applications

Chalcogenide phase-change materials (PCMs) are one of the most mature candidates for next-generation memory technology. Recently, CrGeTe3 (CrGT) emerged as a promising PCM due to its enhanced amorphous stability and fast crystallization for embedded memory applications. The amorphous stability of CrGT was attributed to the complex layered structure of the crystalline motifs needed to initiate crystallization. A subsequent computational screening work identified several similar compounds with good thermal stability, such as InGeTe3, CrSiTe3 and BiSiTe3. Here, we explore substitution of Cr in CrGT with other 3d metals, and predict four additional layered alloys to be dynamically stable, namely, ScGeTe3, TiGeTe3, ZnGeTe3 and MnGeTe3. Thorough ab initio simulations performed on both crystalline and amorphous models of these materials indicate the former three alloys to be potential PCMs with sizable resistance contrast. Furthermore, we find that crystalline MnGeTe3 exhibits ferromagnetic behavior, whereas the amorphous state probably forms a spin-glass phase. This makes MnGeTe3 a promising candidate for magnetic phase-change applications.

cond-mat.mtrl-sci↗

arXiv2023

Spin glass behavior in amorphous Cr2Ge2Te6 phase-change alloy

The layered crystal structure of Cr2Ge2Te6 shows ferromagnetic ordering at the two-dimensional limit, which holds promise for spintronic applications. However, external voltage pulses can trigger amorphization of the material in nanoscale electronic devices, and it is unclear whether the loss of structural ordering leads to a change in magnetic properties. Here, we demonstrate that Cr2Ge2Te6 preserves the spin-polarized nature in the amorphous phase, but undergoes a magnetic transition to a spin glass state below 20 K. Quantum-mechanical computations reveal the microscopic origin of this transition in spin configuration: it is due to strong distortions of the Cr-Te-Cr bonds, connecting chromium-centered octahedra, and to the overall increase in disorder upon amorphization. The tunable magnetic properties of Cr2Ge2Te6 could be exploited for multifunctional, magnetic phase-change devices that switch between crystalline and amorphous states.

cond-mat.mtrl-sci↗

arXiv2021

Density dependent local structures in InTe phase-change materials

Chalcogenide phase-change materials (PCMs) based random access memory (PCRAM) is one of the leading candidates for the development of non-volatile memory and neuro-inspired computing technologies. Recent work shows Indium to be an important alloying element for PCRAM, while a thorough understanding of the parent compound InTe, in particular, its amorphous phase, is still lacking. In this work, we carry out ab initio simulations and chemical bonding analyses on amorphous and various crystalline polymorphs of InTe. We reveal that the local geometries are highly density dependent in amorphous structures, forming In-centered tetrahedral motifs under ambient conditions but defective octahedral motifs under pressure, which stems from the bonding characters of its crystalline polymorphs. In addition, our ab initio molecular dynamics simulations predict rapid crystallization capability of InTe under pressure. At last, we make a suggestion for better use of Indium and propose an "active" device design to utilize both thermal and mechanical effects for phase-change applications.

cond-mat.mtrl-sci↗