查看更多>>摘要：We theoretically study nonlinear thermoelectric transport through a topological superconductor nanowire hosting Majorana bound states(MBSs)at its two ends,a system named as Majorana nanowire(MNW).We consider that the MNW is coupled to the left and right normal metallic leads subjected to either bias voltage or temperature gradient.We focus our attention on the sign change of nonlinear Seebeck and Peltier coefficients induced by mechanisms related to the MBSs,by which the possible existence of MBSs might be proved.Our results show that for a fixed temperature difference between the two leads,the sign of the nonlinear Seebeck coefficient(thermopower)can be reversed by changing the overlap amplitude between the MBSs or the system equilibrium temperature,which are similar to the cases in linear response regime.By optimizing the MBS-MBS interaction amplitude and system equilibrium temperature,we find that the temperature difference may also induce sign change of the nonlinear thermopower.For zero temperature difference and finite bias voltage,both the sign and magnitude of nonlinear Peltier coefficient can be adjusted by changing the bias voltage or overlap amplitude between the MBSs.In the presence of both bias voltage and temperature difference,we show that the electrical current at zero Fermi level and the states induced by overlap between the MBSs keep unchanged,regardless of the amplitude of temperature difference.We also find that the direction of the heat current driven by bias voltage may be changed by weak temperature difference.
查看更多>>摘要：We conduct a detailed examination of the magnetic and electrical transport properties in GdAlSi and SmAlGe crys-tals,which possess a LaPtSi-type structure(space group I41md).The magnetic susceptibility data unambiguously reveal magnetic ordering below a characteristic transition temperature(TN).For GdAlSi,a hysteresis loop is observed in the mag-netization and magnetoresistance curves within the ab plane when the magnetic field is applied below TN,which is around 32 K.Notable specific heat anomalies are detected at 32 K for GdAISi and 6 K for SmAlGe,confirming the occurrence of magnetic transitions.In addition,the extracted magnetic entropy at high temperatures is consistent with the theoretical value of Rln(2J+1)for J=7/2 in Gd3+and J=5/2 in Sm3+,respectively.SmAlGe also exhibits Schottky-like specific heat contributions.Additionally,both GdAlSi and SmAlGe exhibit positive magnetoresistance and a normal Hall effect.
查看更多>>摘要：In high temperature cuprate superconductors,it was found that the superfluid density decreases with the increase of hole doping.One natural question is whether there exists normal fluid in the superconducting state in the overdoped region.In this paper,we have carried out high-resolution ultra-low temperature laser-based angle-resolved photoemission measurements on a heavily overdoped Bi2212 sample with a Tc of 48 K.We find that this heavily overdoped Bi2212 remains in the strong coupling regime with 2△0/(kBTc)=5.8.The single-particle scattering rate is very small along the nodal direction(～5 meV)and increases as the momentum moves from the nodal to the antinodal regions.A hard superconducting gap opening is observed near the antinodal region with the spectral weight at the Fermi level fully suppressed to zero.The normal fluid is found to be negligibly small in the superconducting state of this heavily overdoped Bi2212.These results provide key information to understand the high Tc mechanism in the cuprate superconductors.
查看更多>>摘要：Kagome magnets have attracted considerable research attention due to the interplay between topology,magnetism and electronic correlations.In this study we report single-crystal synthesis of a series of the kagome magnets RCr6Ge6(R=Gd-Tm)that possess defect-free Cr kagome lattices and systematically study their magnetic and electrical trans-port properties.The transition from a canted ferrimagnetic to a paramagnetic state in GdCr6Ge6,TbCr6Ge6,DyCr6Ge6,HoCr6Ge6,ErCr6Ge6 and TmCr6Ge6 occurs at 11.3 K,10.8 K,4.3 K,2.5 K,3.3 K and below 2 K,respectively,due to R-R interactions within the compounds.Magnetization measurements reveal highly anisotropic magnetism with canted magnetic moments in these compounds.In electrical transport,both negative and positive magnetoresistances at different magnetic fields and temperatures have been observed due to the competition between different scattering mechanisms.This work enriches our understanding of the Cr-based kagome magnets and paves the way to search for possible topological responses in this family.
查看更多>>摘要：Based on the force-heat equivalence energy density principle,a theoretical model for magnetic metallic materials is developed,which characterizes the temperature-dependent magnetic anisotropy energy by considering the equivalent relationship between magnetic anisotropy energy and heat energy;then the relationship between the magnetic anisotropy constant and saturation magnetization is considered.Finally,we formulate a temperature-dependent model for saturation magnetization,revealing the inherent relationship between temperature and saturation magnetization.Our model predicts the saturation magnetization for nine different magnetic metallic materials at different temperatures,exhibiting satisfactory agreement with experimental data.Additionally,the experimental data used as reference points are at or near room temper-ature.Compared to other phenomenological theoretical models,this model is considerably more accessible than the data required at 0 K.The index included in our model is set to a constant value,which is equal to 10/3 for materials other than Fe,Co,and Ni.For transition metals(Fe,Co,and Ni in this paper),the index is 6 in the range of 0 K to 0.65Tcr(Tcr is the critical temperature),and 3 in the range of 0.65Tcr to Tcr,unlike other models where the adjustable parameters vary according to each material.In addition,our model provides a new way to design and evaluate magnetic metallic materials with superior magnetic properties over a wide range of temperatures.
查看更多>>摘要：We theoretically investigate the Ruderman-Kittel-Kasuya-Yosida(RKKY)interaction in helical higher-order topo-logical insulators(HOTIs),revealing distinct behaviors mediated by hinge and Dirac-type bulk carriers.Our findings show that hinge-mediated interactions consist of Heisenberg,Ising,and Dzyaloshinskii-Moriya(DM)terms,exhibiting a decay with impurity spacing z and oscillations with Fermi energy εF.These interactions demonstrate ferromagnetic behaviors for the Heisenberg and Ising terms and alternating behavior for the DM term.In contrast,bulk-mediated interactions include Heisenberg,twisted Ising,and DM terms,with a conventional cubic oscillating decay.This study highlights the nuanced interplay between hinge and bulk RKKY interactions in HOTIs,offering insights into designs of next-generation quantum devices based on HOTIs.
查看更多>>摘要：Cubic Mn2RuxGa Heusler compound is a typical example of compensated ferrimagnet with attractive potential for high-density,ultrafast,and low-power spintronic applications.In the form of epitaxial thin films,Mn2RuxGa exhibits high spin polarization and high tunability of compensation temperature by freely changing the Ru content x in a broad range(0.3＜x＜1.0).Herein Mn-Ru-Ga-based polycrystalline bulk buttons prepared by arc melting are systematically studied and it is found that in equilibrium bulk form,the cubic structure is unstable when x＜0.75.To overcome this limitation,Mn-Ru-Ga is alloyed with a fourth element V.By adjusting the content of V in the Mn2Ru0.75VyGa and Mn2.25-yRu0.75VyGa quaternary systems,the magnetic compensation temperature is tuned.Compensation is achieved near 300 K which is confirmed by both the magnetic measurement and anomalous Hall effect measurement.The analyses of the anomalous Hall effect scaling in quaternary Mn-Ru-V-Ga alloy reveal the dominant role of skew scattering,notably that contributed caused by the thermally excited phonons,in contrast to the dominant intrinsic mechanism found in many other 3d ferromagnets and Heusler compounds.It is further shown that the Ga antisites and V content can simultaneously control the residual resistivity ratio(RRR)as well as the relative contribution of phonon and defect to the anomalous Hall effect a''/a'in Mn-Ru-V-Ga,resulting in a scaling relation a"/a'∝RRR1.8.
查看更多>>摘要：Skyrmions,with their vortex-like structures and inherent topological protection,play a pivotal role in developing in-novative low-power memory and logic devices.The efficient generation and control of skyrmions in geometrically confined systems are crucial for the development of skyrmion-based spintronic devices.In this study,we focus on investigating the non-reciprocal transport behavior of skyrmions and their interactions with boundaries of various shapes.The shape of the notch structure in the nanotrack significantly affects the dynamic behavior of magnetic skyrmions.Through micromagnetic simulation,the non-reciprocal transport properties of skyrmions in nanowires with different notch structures are investigated in this work.
查看更多>>摘要：The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under sub-picosecond laser irradiation are investigated using molecular dynamics(MD)simulations and experiments.The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms,which has laser-induced high stress.However,under high fluence and short pulse width laser irradiation,the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film.In addition,Mg[0001]has higher pressure sensitivity and is more prone to ablation than Mg[1 010].The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments.The results show that,under multiple pulsed laser irradiation,not only does the crater depth increase linearly with the pulse number,but also the quadratic term and constant term of the fitted crater profile curve increase linearly.
查看更多>>摘要：Single-molecule magnetic tweezers(MTs)have revealed multiple transition barriers along the unfolding pathway of several two-state proteins,such as GB1 and Csp.In this study,we utilized MTs to measure the force-dependent folding and unfolding rates of both protein L(PLWT)and its Y47W mutant(PLY47W)where the mutation point is not at the force-bearing β-strands.The measurements were conducted within a force range of 3-120 pN.Notably,the unfolding rates of both PLWT and PWY47W exhibit distinct force sensitivities below 50 pN and above 60 pN,implying a two-barrier free energy landscape.Both PLWT and PLY47W share the same force-dependent folding rate and the same transition barriers,but the unfolding rate of PLY47W is faster than that of PLWT.Our finding demonstrates that the residue outside of the force-bearing region will also affect the force-induced unfolding dynamics.
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