Majorana tunneling in a one-dimensional wire with non-Hermitian double quantum dots

The combination of non-Hermitian physics and Majorana fermions can give rise to new effects in quantum transport systems. In this work, we investigate the interplay of PT-symmetric complex potentials, Majorana tunneling and interdot tunneling in a non-Hermitian double quantum dots system. It is found that in the weak-coupling regime the Majorana tunneling has pronounced effects on the transport properties of such a system, manifested as splitting of the single peak into three and a reduced 1/4 peak in the transmission function. In the presence of the PT-symmetric complex potentials and interdot tunneling, the 1/4 central peak is robust against them, while the two side peaks are tuned by them. The interdot tunneling only induces asymmetry, instead of moving the conductance peak, due to the robustness of the Majorana modes. There is an exceptional point induced by the union of Majorana tunneling and interdot tunneling. With increased PT-symmetric complex potentials, the two side peaks will move towards each other. When the exceptional point is passed through, these two side peaks will disappear. In the strong-coupling regime, the Majorana fermion induces a 1/4 conductance dip instead of the three-peak structure. PT-symmetric complex potentials induce two conductance dips pinned at the exceptional point. These effects should be accessible in experiments.

纳米材料锰掺杂量子点中的近藤效应

采用非平衡格林函数方法,探讨了量子点掺杂锰原子纳米材料的低温输运特性。结果表明,输运受到掺杂锰原子的强烈影响。具体来说,在微分电导中出现(2S+1)个近藤劈裂峰,锰原子表现为一个多值量子化有效磁场,导致这种劈裂。

新能源材料及其在电池中的应用

新能源的开发与研究是降低碳排放、优化自然环境、实现可持续发展的重要保障,而新能源材料的研究则是新能源研究的基础环节,是新能源技术发展的前提。本文主要介绍了电池应用领域新能源材料的研究进度与取得的成就,并分析了各种材料的优劣,希望对新能源材料的研究工作能够有所帮助。

马约拉纳费米子与杂质自旋相互作用的热偏压输运

本文研究量子输运中马约拉纳费米子与杂质自旋的相互作用,发现系统能够产生温差驱动的自旋相关电流,得到了马约拉纳费米子导致的热自旋流.在大温差下,马约拉纳费米子与量子点强耦合时,电流与门电压趋于线性关系,体现了马约拉纳费米子的鲁棒性,且马约拉纳费米子导致的自旋流具有振荡特性,其零点个数与杂质自旋角量子数相关.

Negative tunnel magnetoresistance in a quantum dot induced by interplay of a Majorana fermion and thermal-driven ferromagnetic leads

We investigate the spin-related currents and tunnel magnetoresistance through a quantum dot,which is side-coupled with a Majorana fermion zero mode and two thermal-driven ferromagnetic electrodes.It is found that the interplay of Majorana fermion and electrodes'spin polarization can induce a nonlinear thermal-bias spin current.This interplay also decreases the total magnitude of spin or charge current,in either parallel or antiparallel configuration.In addition,a thermal-driven negative tunnel magnetoresistance is found,which is an unique feature to characterize Majorana fermion.With large temperature difference,a step phenomenon is observed in gate tuned spin-up current.When the coupling between quantum dot and topological superconductor is strong enough,this step will evolve into a linear relation,revealing Majorana fermion's robustness.

Phonon-Assisted Spin Current in Single Molecular Magnet Junctions

Owing to the bistable character of the single molecular magnet （SMM）, it can generate 100% spin-polarized currents even connected with normal （N） leads. In this work, we study the phonon-assisted spin current in N- SMM-N systems. We mainly focus on the interplay of SMM＇s bistable character and electron-phonon coupling. It is found that when SMM is trapped in one of the lowest bistable states, it can generate phonon-assisted spin- polarized currents. At the up-spin transport channel, it is accompanied by a phonon-assisted up-spin current, while at the down-spin transport channel, it is accompanied by a phonon-assisted down-spin current.

Multi-step shot noise spectrum induced by a local large spin

We use non-equilibrium Green＇s function method to analyze the shot noise spectrum of artificial single molecular magnets（ASMM） model in the strong spin–orbit coupling limit in sequential tunneling regime, mainly focusing on the effects of local large spin. In the linear response regime, the shot noise shows 2S ＋ 1 peaks and is strongly spin-dependent.In the nonlinear response regime, one can observe 2S ＋ 1 steps in shot noise and Fano factor. In these steps one can see the significant enhancement effect due to the spin-dependent multi-channel process of local large spin, which reduces electron correlations.

Transport through artificial single-molecule magnets:Spin-pair state sequential tunneling and Kondo effects

The transport properties of an artificial single-molecule magnet based on a CdTe quantum dot doped with a single Mn＋2 ion（S=5/2） are investigated by the non-equilibrium Green function method.We consider a minimal model where the Mn-hole exchange coupling is strongly anisotropic so that spin-flip is suppressed and the impurity spin S and a hole spin s entering the quantum dot are coupled into spin pair states with（2S＋1） sublevels.In the sequential tunneling regime,the differential conductance exhibits（2S＋1） possible peaks,corresponding to resonance tunneling via（2S＋1） sublevels.At low temperature,Kondo physics dominates transport and（2S＋1） Kondo peaks occur in the local density of states and conductance.These peaks originate from the spin-singlet state formed by the holes in the leads and on the dot via higher-order processes and are related to the parallel and antiparallel spin pair states.

利用羊骨碳粉研制骨质瓷坯料

骨质瓷是高档日用瓷品种之一,具有洁白细腻、透光性好、釉面光滑等特点,其基础原料骨碳粉常使用牛骨碳。本试验以羊骨碳代替牛骨碳,添加38%的黏土,采用三角配料法优化石英、长石和羊骨碳粉的配比。结果表明,当配比为羊骨碳48.75%、长石6.25%、石英7%,坯体在1280℃下烧成时,其吸水率低于0.2%,透光率为18.9%,主晶相为β-磷酸钙、钙长石和少量残余石英。

新骨瓷坯料配方研制

采用长石或瓷石代替部分骨碳,再配以大同土、龙岩土、球黏土、紫木节土和石英砂等构成新骨瓷的坯体配方。利用三角配料法以吸水率、变形量和透光率为评价指标优选出最佳配方,利用热重-差热分析(TG-DTA)、X射线衍射(XRD)对试样进行表征。结果表明,优化后新骨瓷的化学组成(w/%)为:SiO2,42.33;Al2O3,18.68;CaO,16.72;MgO,1.36;K2O,1.61;Na2O,0.82;P2O5,12.54。1 220℃时烧成新骨瓷的主晶相为β-磷酸钙、钙长石及少量残余石英,具有与骨质瓷相当的透光性和洁白度。