High-entropy enabled two-dimensional ferroelectricity and memristive synapses in van der Waals layered materials – Dr. Runze Yu

Two-dimensional ferroelectric materials offer opportunities for ultrathin non-volatile electronics, but their development is limited by stringent structural requirements for intrinsic polarity. New research from a team of scientists co-led by Dr. Runze Yu from HPSTAR demonstrates that high-entropy engineering can induce switchable polarization in centrosymmetric two-dimensional van der Waals crystals, enabling coupled ferroelectric-like, memristive, and neuromorphic functions. The related results are published in Nature Communications.

Two-dimensional ferroelectric materials hold great promise for ultrathin nonvolatile memories, low-power electronics, and neuromorphic computing. However, their development has been largely constrained by stringent structural requirements, as conventional ferroelectricity typically relies on intrinsically non-centrosymmetric lattices or highly ordered atomic configurations. This symmetry-driven paradigm substantially limits the accessible material space and makes it challenging to realize switchable polarization in centrosymmetric van der Waals crystals. High-entropy materials, featuring multicomponent configurational disorder, local lattice distortions, and heterogeneous coordination environments, offer an alternative route to reshape polarization landscapes and ionic migration pathways. Nevertheless, whether high-entropy engineering can induce ferroelectric-like states and associated memory functionalities in two-dimensional van der Waals materials has remained largely unexplored.

In this work, the authors develop a high-entropy structural engineering strategy based on layered (MnFeCoNi)_1-xCd_xPS₃ single crystals. Despite retaining an average centrosymmetric lattice, multielement mixing generates pronounced local lattice distortions and heterogeneous coordination environments that facilitate electric-field-driven interlayer migration of Cd²⁺, transforming the nonpolar lattice into metastable polar states. The optimized (MnFeCoNi)_0.5Cd_0.5PS₃ exhibits ferroelectric-like switching at approximately ±0.5 V and a transition temperature of up to 523 K. Spectroscopic characterization and density functional theory calculations identify Cd²⁺ as the dominant mobile species and reveal that weak Cd-S bonding and the high-entropy-regulated migration-energy landscape underpin the switchable polarization. The same ionic migration simultaneously modulates electronic transport, giving rise to nonvolatile resistive switching and neuromorphic functions including long-term potentiation, paired-pulse facilitation, and highly linear bidirectional synaptic weight modulation. By linking ferroelectric-like polarization, memristive dynamics, and synaptic plasticity to a common high-entropy-regulated ionic migration mechanism, this work establishes high-entropy engineering as a strategy for generating emergent polar states beyond the conventional requirement of intrinsic non-centrosymmetry and provides a versatile platform for reconfigurable memory and neuromorphic electronics.

 Schematic of the high-entropy ferroelectric memristor and its ion-migration-mediated synaptic mechanism. Representative structural, ferroelectric, and synaptic characteristics of (MnFeCoNi)_1-xCd_xPS₃ are shown below.

开发兼具低功耗和多功能集成能力的二维铁电材料，是面向新型非易失存储与神经形态计算的重要科学问题。然而，传统二维铁电通常依赖本征非中心对称结构或高度有序的原子排列，严格的对称性要求显著限制了材料体系。近年来，高熵材料凭借多组分无序、局域晶格畸变和丰富配位环境，为调控极化行为与离子迁移提供了新的思路。近期，北京高压科学研究中心（HPSTAR）于润泽研究员联合北京邮电大学毕科教授、吴永乐教授、黄凯教授等团队在该领域取得重要进展。该研究以二维层状金属磷硫化物NiPS₃为模型体系，构筑高 (MnFeCoNi)_1-xCd_xPS₃单晶，并提出利用高熵局域结构调控离子迁移、在中心对称晶格中诱导可切换极化的新机制。多组元随机占位形成显著局域晶格畸变和异质配位环境，为Cd²⁺电场驱动层间迁移提供了丰富的亚稳态路径。同步辐射谱学和理论计算表明，Cd²⁺具有较弱的Cd-S相互作用和更低的迁移能垒，是电场作用下的主要迁移离子；高熵局域畸变进一步重塑其迁移能量景观并稳定极性亚稳态，从而实现中心对称晶格向可切换极化状态转变。 优化后的(MnFeCoNi)_0.5Cd_0.5PS₃表现出约±0.5 V的低电压铁电样开关行为，极化转变温度最高可达523 K。同时，Cd²⁺迁移还可调控电子输运，使材料兼具非易失忆阻与神经突触功能，实现长时程增强、双脉冲易化和近线性的双向权重调节，非易失电导保持超过1000 s。 该研究建立了“高熵局域结构—离子迁移—极化亚稳态—忆阻与突触功能”之间的内在联系，为突破二维铁电对本征非中心对称结构的依赖，以及发展可编程极化和神经形态电子材料提供了新的设计思路。相关成果以“High-entropy enabled two-dimensional ferroelectricity and memristive synapses in van der Waals layered materials”为题发表于Nature Communications。