Electrical switching of Ising-superconducting nonreciprocity for quantum neuronal transistor

Nonreciprocal quantum transport effect is mainly governed by the symmetry breaking of the material systems and is gaining extensive attention in condensed matter physics. Realizing electrical switching of the polarity of the nonreciprocal transport without external magnetic field is essential to the development of nonreciprocal quantum devices. However, electrical switching of superconducting nonreciprocity remains yet to be achieved. Here, we report the observation of field-free electrical switching of nonreciprocal Ising superconductivity in Fe3GeTe2/NbSe2 van der Waals (vdW) heterostructure. By taking advantage of this electrically switchable superconducting nonreciprocity, we demonstrate a proof-of-concept nonreciprocal quantum neuronal transistor, which allows for implementing the XOR logic gate and faithfully emulating biological functionality of a cortical neuron in the brain. Our work provides a promising pathway to realize field-free and electrically switchable nonreciprocity of quantum transport and demonstrate its potential in exploring neuromorphic quantum devices with both functionality and performance beyond the traditional devices.


Introduction
Nonreciprocity is an inherent property of materials describing the inequality of the electric or optical signals traveling in opposite directions.This nonreciprocity is usually strongly correlated to the intricate interplay among various types of symmetry breaking, such as inversion symmetry, time-reversal symmetry and mirror symmetry 1- 7 .Manipulation of the nonreciprocity by switching the polarized states resulting from the spontaneous symmetry breaking could give unique opportunities for developing future technologies.Particular interest in this field lies in the nonreciprocal superconducting transport [8][9][10][11][12][13][14][15][16][17][18] , which could be exploited to develop next-generation electronic devices that have ultralow dissipation and new functionalities, such as electronic synapses and neurons [19][20][21][22][23][24][25] .A key step for that purpose is achieving electrical switching of the nonreciprocal superconductivity without the assistant of external magnetic field, but the electrically switchable nonreciprocal superconductivity is still absent.It's worth noting that the polarity of such superconducting diode effect is usually strongly entwined with the breaking mechanisms of time-reversal symmetry and crystalline symmetry 26 .To that end, searching unconventional superconductors with magnetization-or ferroelectricitydetermined nonreciprocity would give a unique opportunity for electrically switching the superconducting diode behavior by reversing those polarized symmetry-broken states 13,27 .
In this work, we demonstrate the electrically switchable nonreciprocal Ising superconductivity at zero magnetic field in a perpendicular-anisotropy Isingsuperconducting (PAIS) quantum material.The PAIS material is synthesized by stacking a layered Ising superconductor, which has Ising-type spin-orbit coupling (SOC) 28 , onto a vdW magnet of perpendicular anisotropy 29 .With the high-quality vdW interface, strong magnetic proximity is induced in the Ising superconductor and breaks time-reversal symmetry, leading to emergence of field-free nonreciprocal Ising-superconductivity, i.e., superconducting diode effect.Moreover, the polarity of nonreciprocal superconductivity in the PAIS device can be switched by electrically reversing the magnetization at zero magnetic field through current-induced out-ofplane spin accumulation.Based on the electrical manipulation of this magnetizationdetermined superconducting diode effect, the proposed nonreciprocal neuronal transistor can implement XOR logic gate and faithfully emulate the biological functionality of a cortical neuron in the brain.Our work demonstrates that the electrical switching of nonreciprocal quantum transport in the condensed matter systems shows great potential in neuromorphic computing.

Field-free and magnetization-determined superconducting diode
The PAIS device was fabricated by stacking vdW magnet Fe3GeTe2 (FGT) and Ising superconductor 2H-NbSe2 (Fig. 1a and 1b).We carried out measurements of the longitudinal resistance under different temperatures.A typical PAIS device with fivelayer NbSe2 (see the atomic force microscope images and corresponding height profiles in Supplementary Fig. 1) exhibits a superconducting behavior with a transition temperature of Tc ≈ 2.95 K (Fig. 1c).To characterize the magnetization of the PAIS material, we measured the Hall resistance under various magnetic field (Supplementary Fig. 2).The results show hysteresis loops of Hall resistance which shrink as temperature increases, indicating that the PAIS device possesses switchable perpendicular magnetization states, denoted as magnetization "UP" and "DOWN" states.
We then investigated the superconducting behaviors under different magnetization states.We first set the magnetization state of the device as "UP" and swept the d.c.current under different perpendicular magnetic fields  z , and monitored the longitudinal resistance at the temperature of 1.6 K.As shown in Fig. 1d Here, Δ c > 0 and Δ c < 0 corresponds to the "+" and "-" polarity, respectively.Notably, as  z is set to zero, a significant nonreciprocal supercurrent with "+" polarity still exists, suggesting the emergence of superconducting diode effect does not require external field.This nonreciprocity with "+" polarity is retained until  z = −10 mT and eventually reversed to that with "-" polarity (i.e., Δ c < 0).When the magnetic field further increases, the nonreciprocal supercurrent Δ c is then suppressed beyond certain magnetic field due to field-induced breakdown of superconductivity (Supplementary Fig. 5).In contrast, we observed the nonreciprocal supercurrent with same magnitude but opposite polarity, when the magnetization is switched to the "DOWN" state (Fig. 1f-g).Such nonreciprocity of superconducting transport can persist to zero external magnetic field in our PAIS device.This is in stark contrast to that reported in nonmagnetic superconducting device 8 , in which the nonreciprocal superconducting transport only emerges at nonzero external magnetic field.Such zero-field superconducting diode effect can produce a large nonreciprocal efficiency, defined by  = , up to 13% at 1.6 K, which is much larger than the value (6% at 0.9 K) previously reported in NbSe2based heterostructure 16 .Since the direction of electrical transport is perpendicular to the magnetization, the observed nonreciprocal superconductivity is similar to magneto-toroidal nonreciprocal directional dichroism (NDD) effect 5 .Note that the nonreciprocal superconducting behavior is determined by the magnetization state in our PAIS device.Electrical switching of the magnetization is thus critical for developing ultralow-power electronic devices based on the superconducting diode effect.

Field-free electrical switching of superconducting diode
We demonstrated that such electrical switching of the polarity of nonreciprocal superconductivity in the PAIS device can be realized through d.c.current pulse.We first swept the pulsed d.c.current Ipulse applied to the PAIS device at 1.6 K and monitored the change in the Hall resistance, with the corresponding results presented in Fig. 2a.At zero magnetic field, sweeping Ipulse upwards or downwards to a critical value can change the sign of the Hall resistance.This phenomenon is consistent with the anomalous Hall effect observed in the same device (Fig. 2b), confirming that the d.c.current pulse can switch the magnetization state in the PAIS device.To be specific, a positive current pulse favours the reversal of the magnetization to "UP" state, while a negative current pulse switches the magnetization to "DOWN" state.
Such field-free electrical switching of magnetization could enable the electrical manipulation of nonreciprocal superconducting transport due to the intrinsic intertwinement of magnetization and nonreciprocal superconductivity.As shown in Fig. 2c, after applying a positive current pulse (Ipulse =+10 mA), we observed the field-free nonreciprocal superconductivity with "+" polarity, consistent with the behavior of magnetization "UP" state demonstrated in Fig. 1d.By contrast, a negative current pulse (Ipulse =-10 mA) can switch the nonreciprocal superconductivity with "+" polarity to its opposite, which is consistent with the behavior of magnetization "DOWN" state shown in Fig. 1f.Such electrical switching of the nonreciprocal Ising superconductivity could provide a promising pathway for the development of novel nonreciprocal electronic devices 17 .

Origin of field-free electrically switchable nonreciprocal superconductivity
We infer that the nonreciprocal Ising superconductivity could result from the intricate interplay among the valley-contrasting Ising spin-orbit coupling (SOC) effect, the time-reversal symmetry breaking induced by magnetic proximity effect and the lowered rotation symmetry in the PAIS quantum materials.On the one hand, the ubiquitous strain and lattice mismatch at the vdW interface can break the ℳ  mirror symmetry of the NbSe2, and lead to in-plane electrical polarization (P).This in-plane P and perpendicular magnetization M of PAIS device can form a magneto-toroidal moment 30 , leading to magneto-toroidal NDD with nonreciprocal charge transport.
When charge current is applied, such lowered lattice symmetry at the interface can give rise to valley-asymmetric Berry curvature distribution, and thus lead to valley magnetization with perpendicular anisotropy, which can generate a spin torque and facilitate the switching of magnetization in PAIS device 31 .In this case, the magneto-toroidal NDD can be flipped by electric pulse through the flipping of M with P fixed.
On the other hand, with the current along the zigzag direction, the ℳ  mirror symmetry of this system can also be broken due to the intricate interplay between valley-contrasting triagonal warping and the magnetic proximity effect (see more detailed discussion in Supplementary Materials).As shown in Fig. 3a-b, an upward magnetization enhances the spin polarization in K valley while decreases the spin polarization in K' valley.In conjunction with the asymmetric trigonal warping effects present in the two distinct valleys, a finite momentum of Cooper pairs could emerge in NbSe2.Conversely, a downward magnetization gives rise to the non-zero Cooper pairs momentum in an opposite manner (Fig. 3c-d).Notably, such effect is a quadratic effect compared to the fermi energy which dominates the charge transport properties.
However, the superconducting gap is several orders smaller than the fermi energy, leading to prominent nonreciprocal quantum transport behavior near the superconducting region where superconducting gap is the dominant energy scale.
Such understanding can be further verified by our successful observation of prominent second harmonic behavior near the superconducting transition region (see Supplementary Fig. 6 and Methods for details), which decays fast when the superconductivity is fully suppressed by external magnetic field and the fermi energy becomes the dominate energy scale.To further clarify this mechanism, we employ the generalized Ginzburg-Landau (GL) theory 3,32 in the proximity to the transition temperature   (see methods for details).When the magnetic proximity and trigonal warping effect is considered in the Ising superconductor NbSe2, we demonstrate that the nonreciprocity of superconducting transport is determined by both the external magnetic field Bz and the proximity-induced magnetization   , which is consistent with our experimental results shown in Fig. 2. In addition, the nonreciprocal efficiency  is calculated to be proportional to (  − ) 1/2 , which coincides with our experimental result shown in Supplementary Fig. 7 (see details in Methods).Finally, the calculation shows that the valley-contrasting Ising SOC with triagonal warping effect could also facilitate the generation of current-induced perpendicular spin polarization (see Methods for details), as shown in the inset of Fig. 3e.This currentinduced z-spin could also produce a spin torque at the vdW interface and thus contribute to the switching of the magnetization in the PAIS material (Supplementary Fig. 8).It is noted that this electrically switchable nonreciprocal superconductivity is reproducible and observed in the both PAIS devices with odd-layer and even-layer NbSe2 (see Section IX of the Supplementary Materials).Fully understanding of such electrical switching of superconducting nonreciprocity requires microscopic models considering the details of the magnetic proximity effect and the symmetry breaking at the vdW interface 27,[33][34][35] .

Quantum neuronal transistor based on electrically switchable superconducting diode effect
Taking advantage of the electrically switchable nonreciprocal Ising superconductivity, we propose and demonstrate a proof-of-concept quantum neuronal transistor, which can faithfully emulate the biological functionality of a cortical neuron 36 in the brain, i.e., performing nonlinear computing operations (Fig. 4a).The neural transistor, a tetrode device shown in Fig. 4b, is operated by feeding input and control signals (represented by X and Y) into the NbSe2 film through the electrodes.
The control current pulse signal Y is used for deterministic reversal of the perpendicular magnetization and thus determines the polarity state ("Δ c > 0" and " Δ c < 0 " corresponds to state "1" and "0", respectively) of nonreciprocal superconducting transport.The resulting state would generate a distinct electrical output corresponding to the input current signal X.The output state ("1" or "0") is represented by the resistance (high or low).To demonstrate the function of the proposed transistor, we switched the polarity state of nonreciprocal superconductivity by applying a train of positive and negative current pulses (denoted as  switch ) onto this device (Fig. 4c) and measured the resulting output (Fig. 4d).For the probe current  probe of +39 μA, the ON-state resistance (R ON ) corresponding to the polarity "+" state is smaller than 0.004 Ω, whereas the OFF-state resistance (R OFF ) corresponding to the polarity "-" state is about 9.8 Ω, giving rise to an on/off ratio of 10 3 .This value is two order of magnitude larger than that of MgO-based conventional MTJs 37-39 and one order of magnitude larger than the state-of-the-art value (1,9000%) under similar experimental conditions 40 .Notably, this ratio depends on the lowest resolution of the measurement system and can be further improved by improving the detection precision.We also note that a superconducting transistor based on the distinct physical mechanism has been theoretically proposed in a Josephson junction with chiral magnet 41 .Unlike the Josephson transistor based on the junction structure in that work, our proposed superconducting neuronal transistor is realizable in all-metallic junction-free superconductors.
The quantum neuronal transistor can emulate the biological function of a cortical neuron 36 in the brain, which can classify linearly non-separable inputs.As the polarity of nonreciprocity is in "+" state, the transistor exhibits a threshold response behavior due to current induced transition between the superconducting and normal states, and only spikes (i.e.output jumps from state "0" to state "1" and back to state "0") when receiving negative current pulses of large magnitude (Fig. 4e).In contrast, the transistor with polarity "-" state only spikes when receiving positive current pulses of large magnitude.These threshold response behaviors resemble those features in the cortical neurons capable of executing XOR nonlinear computational function.
Moreover, we show that the neuronal transistor can also realize the function of XOR gate (Fig. 4f).To demonstrate the XOR function, we set the positive current pulse (+39 μA) as input logic state '1' and the negative current pulse (-39 μA) as input logic state '0' in the experiment.As shown in Fig. 4g, when the input state and polarity state are set to (0,1) and (1,0), logic state "1" corresponding to a high resistance can be generated.By contrast, logic state "0" corresponding to a low resistance can be output when the input state and polarity state are set to (0,0) and (1,1).These results indicate that an XOR gate can be realized in a single quantum transistor.Note that this nonlinear Boole logic function cannot be implemented with a single traditional device and is conventionally thought to require multilayered networks [42][43][44] .In addition, the PAIS device allows the simultaneous achievement of the giant on/off ratio (>200,000%) and ultralow resistance area product (≈ 0.1 Ω⋅μm 2 ), which cannot be realized in conventional MTJs (see detailed comparation in Supplementary Fig. 12) but urgently required for ultrahigh-density electronic applications 45,46 .

Discussion
In

Device fabrication and fundamental characterization
We mechanically exfoliated the NbSe and 28.9 nm in thickness, respectively (see the atomic force microscope images and corresponding height profiles in Supplementary Fig. 1).The bottom electrodes (2 nm Ti/30 nm Au) were patterned using the standard electron beam lithography method and deposited by standard electron beam evaporation.Poly(propylene) carbonate (PPC) coated on polydimethylsiloxane (PDMS) was used to pick up the NbSe 2 and FGT flakes and fabricate the heterostructure devices in a glovebox filled with an inert atmosphere to avoid degradation.

Electrical measurements
All the electrical measurements were performed in the Oxford cryostat with magnetic fields of up to 14 T and temperatures between 1.5 and 300 K. To characterize the electric transport state, a Keithley 2636B dual-channel digital source meter or lock-in amplifier (Stanford SR830) was used to inject the d.c. or a.c.current and measure the 4-probe resistance.The a.c.measurements were performed by injecting a.c.current with a frequency of ω (17.777Hz) using lock-in amplifiers (Stanford SR830).In the measurement of electrical switching of magnetization, large current pulses (write current, 200 μs) were first applied by using Keithley 2636B dual-channel digital source meter.After an interval of 5s, the Hall resistance was measured using an alternating current excitation current of 500 μA.

Nonreciprocal critical current originated from finite momentum
We employ the generalized Ginzburg-Landau (GL) theory 3,32 To derive the microscopic GL free energy, the mean-field Hamiltonian is given by The free energy density can be expressed as a functional of the superconducting order parameter Δ, where  is the temperature and the Boltzmann constant   is neglected for simplicity 10 .We expanded the free energy density up to the third order of  and the first order of   and , that is, where  0 =  0 ( −   ) ,  2 = ℏ 2
For simplicity, we express the above free energy density in a more compact form, Denoting  as the angle between  and   axis, i.e.,   =  cos  and   =  sin , we then can obtain Additionally, the order parameter can be optimized by with () < 0, leading to Notice that the momentum dependent current is given by () = 2 which is a direct result of the mirror symmetry ℳ  breaking.In this case, we can expand (  ) around its minimum   0 , where  ̃3 ≡  3    and  is define as  ≡   −   0 .Under this condition, we find the supercurrent is The critical momentum | is then given by   ()| =  = 0.In this way, we can obtain the critical currents   ± corresponding to  = ∓  respectively, As such, the nonreciprocal efficiency is given by (  +   ), (11)   showing the temperature dependence ( ∝ ( −   )

Second harmonic signals
We adopted the well-established time-dependent GL equation, as widely used in previous reports 3,52 , to calculate the second harmonic signal in our device.By introducing a uniform electric field  and setting the vector potential  = −, the GL free energy quadratic in the order parameter reads where (, ) is the time-dependent GL coefficient which can be expressed as Here,  is the generalized magnetic field (i.e.,  =  +  ) and  .The solution of the time-dependent GL equation is given by which also satisfies the boundary condition (, ∞) = 0.Then, the expectation value of the order parameter is In analytical mechanics  can enters through the free energy (More generally, the Lagrangian).Considering infinitesimal variations , we get  = − ∫   ⋅ , an expression used to obtain the current density .Thus, the current density operator is expressed as (17)   with Ω is the volume of the system.The expectation value of the current density is By applying Eq. ( 13), (18), we can obtain the conductivity as where  1 = We then performed the second harmonic measurement 3,53 with sweeping the perpendicular magnetic field at 4.5 K, which corresponds to the superconducting transition regime, for both magnetization "UP" and "DOWN" states.To distinguish the linear and nonlinear component, both the first ( ω ) and second harmonic signals ) of the longitudinal magnetoresistance (Supplementary Fig. 6) are measured using a lock-in amplifier and applying the a.c.excitation current with an amplitude of 8 μA .The superconducting state fades off by increasing the magnetic field, manifested as the magnetoresistance in Supplementary Fig. 6a.We note that the magnetoresistance dip can be shifted to the left or right when the magnetization is reversed from "UP" to "DOWN" state, again indicating the presence of the proximityinduced exchange field  from the magnetization of FGT.We then extracted the value of  = ±10 mT, which is consistent with the critical field  C at which the Δ c vanishes for magnetization "UP" and "DOWN" state (Fig. 1e and Fig. 1g).In addition, the result that the  2ω is antisymmetric with respect to the perpendicular magnetic field and magnetization (Supplementary Fig. 6b), i.e.,  2ω ( − z ,  DOWN ) = − 2ω ( z ,  UP ), which is consistent with the magneto-toroidal nonreciprocal effect.
Notably, the second harmonic signal decays fast as the external magnetic field further increases and the fermi energy becomes the dominate energy scale.This phenomenon confirms the important role of trigonal warping effect on the nonreciprocal superconducting transport in our PAIS device.

Temperature dependence of nonreciprocal superconducting transport
We swept the direct current and monitored the change in resistance under various temperatures ranging from 1.6 to 3.5 K when fixing the magnetization "DOWN" state in a PAIS device with 7-layer NbSe2 (Supplementary Fig. 7a).For each temperature, we observed significant nonreciprocal supercurrent with polarity "+" state see in Supplementary Fig. 7c), consistent with the theoretic analysis (see Methods: Nonreciprocal critical current originated from finite momentum).

Current-induced spin polarization
The coexistence of Ising SOC and trigonal warping at the Fermi surface can also facilitate the generation of current-induced perpendicular spin polarization.
Specifically speaking, the electric field generated from charge current would change the trigonally warped Fermi surfaces of spin-up and spin-down branches in both K and K' valleys and thus lifts the valley degeneracy.This valley population imbalance would generate a z-spin polarization (the inset of Fig. 3e), which could produce a spin torque at the vdW interface and thus switch the magnetization in the PAIS material (Supplementary Fig. 8).To further elucidate the current-induced z-spin polarization, we calculated the current contribution to spin polarization using the Boltzmann equation 34,54 as follows.
The effective Hamiltonian of a monolayer NbSe2 can be written as where   = ±1 represent the valley degrees of freedom.Straightforward diagonalization of this Hamiltonian gives the eigenvalues and eigenvectors For simplicity, we consider a line in the Brillouin zone along the   , where  ± are the different energy-dependent scattering rates.Generally, one can assume that  ± = (1 ± ) with  the relaxation time of the free-electron gas 55 .
Then we calculate analytically the current contribution from each subband using the Boltzmann equation 34,54 , one can get where  ,± and   ± are the electron distribution function and Fermi surfaces for the ± bands, respectively.By choosing  = ℰ ̂ and assuming  ,± =   , one can further get where we apply the relation  = (cos  , sin  , 0).Thus, the total current density is given by The spin expectation value reads Therefore, the spin density can be calculated in an analogous way as which yields the total spin density Consequently, from the two equations (26) (29), we can get    spike to the input current pulses for the polarity "+" and "-" states.e, The XOR function in the nonreciprocal neural transistor.The dashed boxes represent the logic state values for input and polarity combinations (0,1), (1,1), (0,0) and (1,0), respectively.
, sharp jumps of resistance occur as the current reaches a critical value (| c |).When  z is applied in the positive direction of the z-axis (e.g.,  z = +10 mT ), | c | strongly depends on the direction of the current flowing (positive +I or negative -I), indicating the nonreciprocity of the supercurrent, i.e., superconducting diode effect.Such nonreciprocal supercurrent, characterized by Δ c = | c + | − | c − |, is dependent on the applied magnetic field, as shown in Fig. 1e.
2 and FGT flakes onto a highly doped Si wafer covered by a 300-nm-thick SiO2 layer.Before the device fabrication, the crystallographic orientation of the NbSe2 flake was characterized by measuring the co-polarized SHG intensity as a function of relative angle between laser polarization and crystal orientation.In the following fabrication process, we designed the device geometry to set the direction of current along zigzag direction of the NbSe2 sample in the experiments.As shown in Supplementary Fig.14, the maximum (minimum) intensity corresponds to the armchair (zigzag) direction of the crystal, confirming the current flowing along the zigzag direction.The thickness of these flakes were identified with optical contrast and a Bruker MultiMode 8 atomic force microscope.The NbSe2 and FGT flakes of typical PAIS device are approximately 3.1 nm (5 layers)

2 .
In this context, () = (  2 −   2 , −2    ) denotes the nonlinear term of the in-plane electric field.As expected,  2 encapsulates the second harmonic signal, which is prominent near the superconducting transition where the small superconducting gap dominates the electrical transport.

(
represented as Δ c < 0 ).To further clarify the temperature dependence of this nonreciprocal effect, the temperature dependence of nonreciprocal efficiency || are clearly plotted in Supplementary Fig. 7b.With increasing the temperature, this nonreciprocal efficiency || decreases and its temperature dependence is well fitted by a √1 −   c function (the critical temperature  c = 4.8 K

Fig. 2 .
Fig. 2. Electrically switchable nonreciprocal Ising superconductivity.a, Currentinduced magnetization switching at zero field at 1.6 K.The sign of Hall resistance is reversed by sweeping the pulsed current.b, Hall resistance as a function of the perpendicular magnetic field at 1.6 K.The Hall resistance was measured using an a.c.excitation current of 500 μA.c, Schematics (upper panels) and experimental data (lower panels) of electrically switchable nonreciprocal superconducting transport.After applying a positive current pulse (  pulse = +10 mA ), the polarity of nonreciprocal superconductivity is switched to Δ c > 0 , i.e., nonreciprocal supercurrent flowing rightward (left panels).While the negative current pulse ( pulse = −10 mA) favours the reversal to the polarity "-" state, i.e., Δ c < 0 (right

Fig. 3 .
Fig. 3.The mechanism for electrically switchable superconducting diode.a, Fermi surface and spin texture of NbSe 2 based on the tight-binding Hamiltonian in the first Brillouin zone for magnetization "UP" state.The color scale indicates the out-of-plane spin component.The red and blue lines represent the energy bands with the spin "UP" and "DOWN" states, respectively.b, Schematic of magnetic proximity induced finite momentum of Cooper pairs for magnetization "UP" state.The dotted and solid lines represent the energy bands without and with the magnetic proximity effect, respectively.c, Fermi surface and spin texture of NbSe 2 for magnetization "DOWN" state.d, Schematic of magnetic proximity induced a finite momentum of Cooper pairs for magnetization "DOWN" state.e, Calculation of current-induced spin density.Insets are the schematic illustrations of spin distributions changed by the current-induced electric fields.Red and blue lines represent contours of spin-up and spin-down branches, respectively.Orange and green shaded regions represent spin-up and spin-down overpopulation for K and K' valleys, respectively.

Fig. 4 .
Fig. 4. Nonreciprocal neural transistor.a, Schematic structure of a biological cortical neuron.The neuron can classify linearly nonseparable inputs through the nonlinear XOR function.b, Schematic of the neural transistor.Input signals (represented by X and Y) are fed into the NbSe2 film through the electrodes.c, Deterministic switching by a series of current pulses applied in the device.The width and magnitude of the current pulses are 200 μs and 10 mA, respectively.d, The resistance is measured by using a small d.c.excitation current of +39 μA.e, The responses of spike to the input current pulses for the polarity "+" and "-" states.f, Logic function of the neural transistor, in which nonlinear input-output responses depend on the polarity state.g, The XOR function in the nonreciprocal neural transistor.The dashed boxes represent the logic state values for input and polarity combinations (0,1), (1,1), (0,0) and (1,0), respectively.
By taking advantage of this electrically switchable superconducting diode effect, we propose and demonstrate a nonreciprocal quantum neuronal transistor able to perform the XOR function, which is inaccessible with previously reported technology.Our work opens up a promising avenue for neuromorphic computing based on nonreciprocal quantum transport.
summary, we demonstrate field-free electrical switching of Ising superconducting diode effect in the Fe3GeTe2/NbSe2 van der Waals (vdW) heterostructure.