arXiv subjects

Xujin Zhang

Publications and source records attributed to Xujin Zhang.

4 recordsLinked to original sources

arXiv2026

Interface-Engineered Giant Multistate Resistance Switching in Altermagnetic CrSb Multiferroic Tunnel Junctions

Altermagnets enable spin-split transport without stray magnetic fields, yet converting their momentum-dependent spin splitting into a strong tunnel-junction response requires interface-selected tunneling channels. Here, using density functional theory combined with nonequilibrium Green's function calculations, we demonstrate giant multistate resistance switching in CrSb/$α$-In$_2$Se$_3$ altermagnetic multiferroic tunnel junctions. The response is governed not by the bulk spin splitting of CrSb alone, but by a symmetry-selected interfacial mechanism in which Cr/Sb terminations and \textit{h}-BN or graphene insertion layers determine spin-channel matching, while ferroelectric polarization reshapes the electrostatic barrier. Symmetric and asymmetric terminations reverse the correspondence between parallel/antiparallel Néel-vector configurations and high-/low-resistance states, showing that the actual alignment of interfacial Cr moments selects the dominant tunneling channels. Monolayer-In$_2$Se$_3$ junctions exhibit four nonvolatile resistance states, with tunneling magnetoresistance (TMR) and tunneling electroresistance (TER) reaching 1626\% and 2206\%, respectively, and increasing to 9576\% and 4144\% upon Fermi-level shifting. Finite-bias calculations further reveal robust spin filtering and tunable spin-polarized currents. Extending the barrier to bilayer In$_2$Se$_3$ introduces interlayer polarization coupling, enabling eight resistance states with maximum TMR and TER values of $3.77\times10^{4}\%$ and $4.18\times10^{5}\%$, respectively. These results establish interface symmetry, spin-channel matching, and ferroelectric barrier reconstruction as design principles for stray-field-free multistate spintronic tunnel devices.

cond-mat.mtrl-sci↗

arXiv2026

Nonvolatile single-ion memory with picosecond switching

The rapid development of artificial intelligence (AI), Internet of Things (IoT), and edge computing applications has posed severe challenges to conventional memory technologies in terms of density, speed, and energy consumption. Herein, a single-ion transport mechanism is proposed to achieve picosecond (ps) switching capability. For monolayer hexagonal boron nitride (h-BN) with single-atom vacancy defects, first-principles calculations reveal that single-ion penetration across the BN plane dominates the resistive switching. The trapping and release of a single ion correspond to different states of the memory device for one bit of information. Experimentally fabricated single-ion memory exhibits nonvolatile resistive switching with ultra-fast switching speed of 20 ps and ultra-low energy consumption of 310 aJ/bit. This high performance is attributed to the extremely short distance for the single ion to travel through. Such devices pave the way for the realization of high-performance nonvolatile memory with ultra-fast speed, ultra-low energy consumption, and high storage density, that is called the "Unified Memory" long desired by the whole industry.

physics.app-ph↗

arXiv2025

Giant Nonvolatile Multistate Resistance with Fully Magnetically Controlled van der Waals Multiferroic Tunnel Junctions

Ferroelectric polarization switching in electrically controlled van der Waals multiferroic tunnel junctions (vdW-MFTJs) causes atomic migration, compromising device stability and fatigue resistance. Here we propose a fully magnetically controlled vdW-MFTJ based on a $\mathrm{CrBr_3/MnPSe_3/CrBr_3}$ vertical heterostructure, which achieves ferroelectric polarization reversal without relying on atomic migration driven by inversion symmetry breaking. Using first-principles calculations, we investigate the spin-polarized quantum transport properties of the proposed structure. By integrating asymmetric PtTe$_2$/alkali-metal (Li/Na/K)-doped/intercalated CrBr$_3$ electrodes, the device demonstrates exceptional performance, with a maximum tunneling magnetoresistance (TMR) exceeding $8.1\times10^5$\% and tunneling electroresistance (TER) reaching 2499\%, while the spin-filtering channels can be flexibly controlled by the magnetization direction of the magnetic free layer, achieving perfect spin-filtering over a broad bias voltage range. Applying an external bias voltage further enhances these metrics, increasing TMR to $3.6\times 10^7$\% and TER to 9990\%. Notably, a pronounced negative differential resistance (NDR) effect is observed, yielding an unprecedented peak-to-valley ratio (PVR) of $9.55\times10^9$\%, representing the highest value reported for vertical tunnel junctions. These extraordinary characteristics highlight the potential of vdW-MFTJs for ultra-efficient electronic switching, a key feature for next-generation spintronic devices. Our findings provide a solid theoretical foundation for designing and developing high-performance magnetic storage and logic technologies.

cond-mat.mtrl-sci↗

arXiv2025

Giant Tunneling Magnetoresistance in Graphene/$h$-BN Based van der Waals Magnetic Tunnel Junctions via 3$d$ Transition Metal Intercalation

Atomic intercalation offers a powerful route for engineering two-dimensional (2D) materials by precisely tuning interlayer electronic coupling and spin configurations. Here, we propose a generic strategy for the construction of fully 2D magnetic tunnel junctions (MTJs) based on transition metal-intercalated graphene electrodes with $h$-BN barrier layer. First-principles calculations reveal that intercalation not only stabilizes uniform atomic dispersion via steric hindrance but also induces robust ferromagnetism in graphene. Manganese- and vanadium-intercalated systems (Mn-Gr and V-Gr) exhibit exceptional spintronic performance, with tunneling magnetoresistance (TMR) showing a pronounced odd-even oscillation as a function of barrier thickness. A giant TMR of $4.35 \times 10^8\,\%$ is achieved in the Mn-Gr system with a monolayer barrier $h$ -BN ($n=1$), while V-Gr reaches a maximum TMR of $1.86 \times 10^5\,\%$ for a trilayer barrier ($n=3$). Moreover, biaxial strain further enhances the TMR to $10^9\,\%$ and $10^7\,\%$ in Mn-Gr and V-Gr systems, respectively. The devices also exhibit perfect spin filtering and pronounced negative differential resistance, offering new opportunities for high-performance spintronic and memory applications based on 2D van der Waals heterostructures.

cond-mat.mtrl-sci↗