The anisotropic spin splitting in unconventional magnets opens new opportunities for realizing spintronic functionalities without relying on net magnetization or relativistic spin-orbit coupling. Here, we propose a spin valve and a spin transistor based on unconventional p-wave magnets (UPMs). The spin valve is realized in a junction where a normal metal is sandwiched between two UPMs whose exchange-field strength vectors are oriented transverse to the junction direction. The conductance of such a device is governed by the spin alignment between two UPMs: when their strength vectors are parallel, the spin-state alignment enables efficient electron transmission, leading to a high-conductance state; in contrast, the antiparallel configuration suppresses the conductance owing to the opposite spin orientations. Furthermore, the spin-valve can be extended to a spin transistor by replacing the central normal metal with another UPM with a longitudinally oriented strength vector and a perpendicular spin polarization axis. The central UPM enables uniform spin precession with the same precession frequency for all transverse modes. Both devices can be electrically controlled by modulating the strength vectors of UPMs. These findings establish UPMs as a promising platform for developing spintronic devices without net magnetization or relativistic spin-orbit coupling.

Abstract We investigate the quantized charge pumping in graphene with Rashba spin–orbit coupling (RSOC) under two time-periodic staggered potentials. Surprisingly, the quantized charge pumped per cycle exhibits a sharp dependence on the transverse boundary conditions: a zero quantized charge is obtained under periodic boundary conditions (consistent with bulk thermodynamic limits), whereas a quantized value of 1 per spin emerges under open boundary conditions. This topological transition induced by the transverse boundary conditions persists even for large system widths, revealing a discontinuous crossover from finite to infinite geometries without relying on topological edge states at the boundaries. We attribute this phenomenon to RSOC-induced intravalley reflection at transverse boundaries, which modifies the winding number of the pumping cycle. These results challenge conventional wisdom about finite-to-infinite transitions in condensed matter systems and advance the fundamental understanding of boundary-sensitive quantum transport in multivalley systems.

We study an electron-phonon-interaction-driven thermoelectric diode. The nonreciprocity in this diode arises from the asymmetry between the probabilities of phonon emission and absorption in the electron-phonon interaction, as well as the structural reflection asymmetry. We reveal the intrinsic nature of this nonreciprocity, as the forward and backward electron transport remains asymmetric even when the applied temperature difference is not reversed. This intrinsic nonreciprocity gives rise to two novel transport phenomena. One is a novel thermoelectric effect that is driven by the temperature difference between the leads and the central device region, rather than the conventional temperature difference between the two leads. The second, and more significant, phenomenon is the suppression of electronic backscattering in the load resistor. This suppression decreases the resistance of the load resistor, which leads to the breakdown of Ohm’s addition law. Under suitable conditions, the presence of electron-phonon interaction can yield a larger thermoelectric current compared to the case without it. This intrinsic nonreciprocity opens up a pathway for low-power electronics besides topology and superconductivity, and for nonreciprocal thermoelectric devices.

An identity term in the Hamiltonian is conventionally regarded as spectrally inert-it shifts energies but does not alter eigenstate topology. We show that under non-Hermitian skin pumping, this paradigm fails: a momentum-dependent identity term actively deforms the generalized Brillouin zone, thereby challenging established topological criteria that rely on fixed complex contours. Here, by introducing spin-orbit coupling into a Hatano-Nelson chain, we present an exact analytical solution for the entire non-Hermitian eigensystem under open boundary conditions. Our solution reveals how inter-cell spin-orbit coupling, synergizing with this non-trivial identity term, induces topological edge states and robust zero modes in the complete absence of chiral symmetry. This work establishes an exactly solvable paradigm for non-Hermitian topology beyond symmetry protection, and provides a rigorous benchmark for testing topological invariants in systems with momentum-dependent identity terms.

The material 1 T − TaS 2 with the charge density wave phase can be employed to achieve multiple robust flat bands that depends on the number ( m ) of extra atoms residing on each edge of the hexagon (Lee et al 2020 Phys. Rev. Lett. 124 137002). When m = 1, the 1 T − TaS 2 lattice represents the line-centered honeycomb lattice. We report a theoretical study of the integer quantum Hall effect (IQHE) in the honeycomb superlattice model from the nearly commensurate charge-density-wave phase of 1 T − TaS 2 which has a flat band at band center crossing a single Dirac cone. It is shown that the Dirac electrons exhibit a conventional nonrelativistic IQHE of σ x y = v e 2 / h ( v = 0 , ± 2 , ± 4 , … ) while a zero Hall platform grows at the band center from the electrons of the flat band. The zero-Hall platform can be easily destroyed by the disorder effect due to the band broadening effect. The staggered potential controlled by an external electric field is introduced into the system to open an energy gap and an emergent IQHE is observed in the band gap. The relativistic half-IQHE is also found in the system in the energy region near K and K ′ valleys far away from the band center.

The dice lattice bears a similar honeycomb lattice structure to graphene but with a non-dispersive flat band intersecting the Dirac bands at the band center. In this work, we investigate Nernst effect of the dice lattice in a strong magnetic field, focusing on the role of the flat band. By using the Chebyshev polynomial Green’s function method, we show that no Nernst effect (Sxy=0) is around the Dirac point in the clean limit contrary to the graphene case because of the existence of a zero Hall conductivity platform. However, an unconventional negative Sxy of the double-peak structure emerges instead when the flat band is broadened by disorder and temperature. In addition, when a mass term of Dirac electrons is introduced in the system to open an energy gap, a negative single peak of Sxy appears at the Dirac point and this is due to the derivative quantum Hall effect of non-Dirac electrons in the flat band appearing in the energy gap.

Based on the lattice Green's function technique, we theoretically investigate the topological charge pump driven by two time-dependent staggered potentials in graphene with Rashba spin-orbit coupling. A topological transition occurs with increasing Rashba strength, where the pumped charge in a period changes from 1 to 0 per spin. The transition is attributed to the change of Berry phase from 7r to 27r when the Rashba spin-orbit coupling is turned on. In the gap opened by the staggered potential, the Berry phase becomes the valley Chern number and very sensitive to the Rashba strength. As a consequence, the pumped current undergoes an abrupt transition from 1 to 0 even in the presence of a weak Rashba coupling. This proposal provides a scheme to realize tunable topological transitions in quantized charge pumps.

Organophosphorus (OP) compounds are neurotoxins that are among the most widely used pesticides in agriculture in the United States. In this application, a new integrated point-of-care smartphone/resistive nanosensor device is developed for onsite rapid and sensitive detection of exposure to OP pesticides from a drop of finger-stick blood among a sample of farmworkers. The nanosensor leverages the transport properties of a multiwalled carbon nanotube/polyaniline nanofiber (MWCNT/PAnNF) nanocomposite film on a gold interdigitated electrode and acetylcholinesterase/butyrylcholinesterase (AChE/BChE) hydrolysis of their respective substrates generating protons doping PAnNFs, thereby increasing the conductance of the film. As such, a conductance change can be used to quantify cholinesterase activity, enabling assessment of acute/chronic OP poisoning. Additionally, a mobile app was developed for the nanosensor to process, display, track, and share results. Under optimal conditions, the nanosensor demonstrated exceptional sensitivity with the detection limits of 0.11 U/mL for AChE and 0.093 U/mL for BChE, physiologically relevant dynamic ranges of 2.0-18.0 U/mL for AChE and 0.5-5.0 U/mL for BChE in whole blood, and high reproducibility with the relative standard variation of <4%. The nanosensor was further validated with widely used radiometric and Ellman's methods, utilizing both in vitro pesticide-spiked blood samples and blood samples from 22 farmworkers. The results between this nanosensor and those two methods demonstrated a strong agreement. This platform provides a new avenue for the simple, rapid, and sensitive biomonitoring of OP pesticide exposure.

We investigate the possible Josephson diode effect(JDE)in a two-dimensional(2D)nonmagnetic planar s-wave superconductor junction,which is constructed on a spin-collinear d-wave altermagnet(AM)material in the presence of Rashba spin-orbit interaction.It is demonstrated that the JDE is critically dependent on the crystalline axis of the AM relative to the current direction.The dx2-y2 magnetization symmetry can support a JDE whereas the dxy symmetry does not facilitate it.The JDE efficiency can reach up to 40％and can be adjusted by an additional asymmetric gate voltage applied to the non-superconducting region of the junction,including control of its polarity.Our findings provide an electrical means to control the JDE within a non-magnetic AM-based superconducting junction.

The nonadiabatic holonomic quantum computation based on the geometric phase is robust against the built-in noise and decoherence. In this work, we theoretically propose a scheme to realize nonadiabatic holonomic quantum gates in a surface electron system, which is a promising two-dimensional platform for quantum computation. The holonomic gate is realized by a three-level structure that combines the Rydberg states and spin states via an inhomogeneous magnetic field. After a cyclic evolution, the computation bases pick up different geometric phases and thus perform a holonomic gate. Only the electron with spin up experiences the holonomic gate, while the electron with spin down is decoupled from the state-selective driving fields. The arbitrary controlled-U gate encoded on the Rydberg states and spin states can then be realized. The fidelity of the output state exceeds 0.99 with experimentally achievable parameters.

Disorder is often considered the opposite of order, lacking quantitative methods and being difficult to control. Disordered nanostructures can be conveniently prepared by bottom-up approaches, such as self-assembly, but their intrinsic randomness is often considered to lead to unpredictable results, impeding reproducibility and application. Here, we demonstrate that deterministic, angle-dependent visual appearances induced by specific correlated disorder can be achieved through bottom-up approaches, and reveal plenty of room for tailoring color appearance between order and random disorder. Two unprecedented iridescent visual appearances, backscattering iridescence (rainbow-like color transition covering more than five distinct colors at backscattering angles), and specular iridescent halo (gradual color changes in the visible light range around specular reflection direction), are proposed and demonstrated to be induced by correlated disorder at different degrees, which is regulated by interparticle distance. Besides elucidating the mechanism of iridescence generation, a comprehensive protocol for predicting the color appearance is established, and agrees well with experimental results. Combining bottom-up process, materials with low absorption, and tailored spatial disorder, we have endowed solar cells with colorful appearances, while maintaining the performance, which can serve as a solution for photovoltaic-integrated architectures and vehicles. This study advances the understanding of how disorder shapes color and angular appearance, and will find applications in energy photonics, dazzling arts, and anticounterfeiting.

Dirac electrons possess a valley degree of freedom,which is currently under investigation as a potential information carrier.We propose an approach to generate and manipulate the valley-switching current(VSC)through Andreev reflection using an interferometer-based superconductor hybrid junction.The interferometer comprises a ring-shaped structure formed by topological kink states in the α-T3 lattice via carefully designed electrostatic potentials.Our results demonstrate the feasibility of achieving a fully polarized VSC in this device without contamination from cotunneling electrons sharing the same valley as the incident electron.Furthermore,we show that control over the fully polarized VSC can be achieved by applying a nonlocal gate voltage or modifying the global parameter α.The former alters the dynamic phase of electrons while the latter provides an α-dependent Berry phase,both directly influencing quantum interference and thereby affecting performance in terms of generating and manipulating VSC,crucial for advancements in valleytronics.

Typically, edge states in graphene are known to exist solely along zigzag edges. However, in this paper, we present a theoretical discovery of edge states along armchair edges in graphene under shear strain. This phenomenon arises from shear strain causing a separation between two inequivalent Dirac cones in the Brillouin zone (BZ) along the zigzag direction. Consequently, these armchair edge states appear as flat bands, connecting the two Dirac points at the two edges of armchair graphene nanoribbons (AGNRs). The length of these flat bands in the BZ and the penetration depth of the edge states are directly and inversely proportional to the strain, respectively. In monolayer AGNRs, possible magnetic configurations of flat bands resulting from electron-electron interactions are investigated. The edge-to-edge antiferromagnet (AFM) ground state is found in neutral AGNRs, while the AFM to ferromagnet (FM) transition can occur and be controlled by the strain in low-doped AGNRs. In gapped bilayer AGNRs, the armchair edge states evolve into quantum valley Hall edge states (QVHESs), which significantly improves the conductivity of QVHESs at realistic imperfect sample edges. These armchair edge states present a promising and tunable platform for exploring topological edge states in graphene.

The nonreciprocity of critical supercurrents in a Josephson device, termed the Josephson diode effect (JDE), has drawn considerable interest recently. Herein, we present possible spin-resolved and charge JDEs in a Josephson junction based on the alpha- T-3 lattice, due to different spin-resolved Fermi velocities in opposite directions for the distorted flat bands and edge states. Two mechanisms are exhibited, which are characterized by a topological phase with an anisotropic parameter alpha . One is that the JDE only originates from distorted flat bands, corresponding to the topological phase (0 < alpha < 0 . 5), the other simultaneously from edge states in the topological phase (0.5 . 5 < alpha < 1). Particularly, the charge JDE only manifests in the context of magnetization and its efficiency can range from - 45% to 39%, suggesting a high nonreciprocity. More importantly, both the magnitude and polarity of the charge JDE from edge states and distorted flat bands can be strongly adjusted by the magnetization strength.

- Anomalous Josephson current in an s-wave superconductor junction is due to the parity and time-reversal symmetry breaking from the spin-orbit coupling (SOC) together with magnetization. Altermagnetism is an emerging magnetic phase with the d-wave-type magnetism but zero macroscopic magnetization. Here, we numerically study the Josephson supercurrent in a two-dimensional junction with both the SOC and altermagnetism. It is found that the 0-pi transition can appear in the system by modulating the junction's lengths or the SOC strengths despite the zero net magnetization in the system. An anomalous Josephson effect is also identified but dependent on the orientation of magnetization.

The Josephson diode effect (JDE) is the asymmetry of the critical supercurrent flowing along opposite current directions. We study a mechanism in this work to generate a possible JDE in the two-dimensional line-centered honeycomb (LCH) lattice based Josephson junction in which the supercurrent flows via the topological edge states. Since the two helical edge states of the LCH topological insulator have different Fermi velocities, the field-free Josephson junction is shown to exhibit a spin-resolved JDE in which the critical supercurrent is asymmetric over the two opposite current directions for each spin species. By introducing magnetization in the circuit, a charge version of JDE occurs in the system.

In this paper, we theoretically propose a method to simulate the longitudinal relaxation of a single qubit by coupling it to an auxiliary qubit. In order to mimic the finite-temperature relaxation, we utilize the Hamiltonian-ensemble approach [Kropf, Gneiting, and Buchleitner, Phys. Rev. X 6, 031023 (2016)] and in each realization the auxiliary qubit possesses a random level spacing. The longitudinal relaxation arises as a consequence of the ensemble average and the interaction between the working qubit and the auxiliary qubit. Furthermore, we apply this approach to investigate the influence of the longitudinal relaxation and the transverse relaxation on the entanglement dynamics of two qubits. It is discovered that the sudden death of the entanglement will occur as long as the longitudinal relaxation is present. The transverse relaxation assists the longitudinal relaxation and thus accelerates the finite-time disentanglement.

The Dice lattice structure is similar to the graphene honeycomb lattice, but with an imbalance atom in each hexagon center giving rise to a dispersionless flat band, which intersects the pseudopsin $S=1$ Dirac bands through the Dirac point. In this work, we report a theoretical study on the thermopower of the Dice lattice by focusing on the role of the flat band and comparison with the graphene case. Based on the Chebyshev polynomials Green's function method, we show that an extra pair of thermopower peaks near the band center appear in the Dice lattice compared to the graphene counterpart due to the presence of the flat band. In the relatively high temperature regime, the emergent thermopower peaks exhibit an unconventional dependence on temperature and disorder contrary to the Mott's relation, and the origin is ascribed to the extreme narrow bandwidth of the broadened flat band. We also discuss the enhancement of the thermopower by introducing an energy gap in the Dice lattice.

The alpha-T3 lattice is an interpolate between the graphene (alpha = 0) and the Dice lattices (alpha = 1) and has a nondispersive flat band across the Dirac bands at the band center (E = 0). In this paper, we study the delocalization effect of the additional chiral zero-energy modes (CZEM) from the vacancy disorder in the alpha-T3 lattice and address the influence of the flat band on the CZEM. It is shown that the mere broadening of the flat band without the CZEM could produce a supermetallic phase around the band center E similar to 0 as well as an adjoined narrow localization regime. When the CZEM from the vacancy disorder is turned on, the transport property resembles the graphene case (alpha = 0) that electrons in the low-energy regime are fully localized except the Dirac point of E = 0, which is a critical delocalization point because the zero-energy conductivity (ZEC) is independent of the inelastic-scattering strength q. But the ZEC itself is shown to weakly rely on both the model parameter alpha and the vacancy density nc due to the broadening effect of the flat band. The extreme vacancy imbalance among each ABC site of a primitive cell is also studied, and the electron transport around E similar to 0 is changed to be either the pure inelastic disorder case without vacancy or the fully localized phase without the critical delocalization point of E = 0, which depends on the central site B atom replaced by vacancy or not.

We propose an adiabatic superconducting charge pump based on massive Dirac electrons. A superconductor is sandwiched in between two pumping sources, which are formed by introducing the time-dependent and out-of-phase staggered potentials in graphene as pumping parameters. The pump is shown to be characterized by not only the topological interface state (TIS) but also the non-topologically quasi interface state (QIS). Hereafter, our attention is focused on the pumping currents I L NR and I L AR from the normal and Andreev reflections, respectively, which predominate by making the electron energy reside in the effective energy gap. It is found that modulating the energy E , superconductor length L 0 , and pumping source length L P results in the considerable variation of competitive behaviors between I L NR and I L AR . In particular, the reversal effect of current direction can be realized by tuning L P . More interestingly, the current-phase relationship exhibits the platform behaviors, which can be manipulated by L P and the pumping strength. All the above pumping properties are attributed to the adiabatic evolution of TIS and non-topologically QIS, particularly the conversion between each other is the crucial origin. We also obtain the quantized pumping current by adjusting L P and L 0 , and present the corresponding qualitative explanation through the pumping contour circled by the two parameters. In addition, we discuss the features of pumping current based on the armchair graphene as well.