The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1 / 2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at~300 GeV found by previous experiments and reveals a softening at~13.6 TeV, with the spectral index changing from~2.60 to~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

Spin-dependent tunneling through a symmetric semiconductor barrier is studied including the k 3 Dresselhaus effect. The spin-dependent transmission of electron can be obtained analytically.By comparing with previous work(Phys. Rev. B 67. R201304 (2003) and Phys. Rev. Lett. 93. (2004)), it is shown that the spin polarization and interface current are changed significantly by including the off-diagonal elements in the current operator, and can be enhanced considerably by the Dresselhaus effect in the contact regions.PACS numbers: 72.25. Dc, 72.25.Mk, 73.40.Gk * Correspondence should be sent to: kchang@red.semi.ac.cn 1 Recently electron spin in semiconductors has attracted a rapidly growing interest due to its potential application in spintronics devices. To successfully incorporate spin into existing semiconductor technology, one has to overcome technical difficulties such as efficient spin-polarized injection, transport, control and manipulation, as well as measurement of spin polarization. The injection of spin-polarized electrons from ferromagnetic metals into semiconductors has low efficiency, less than 1%, because of a large resistivity mismatch between ferromagnetic and semiconductor materials [1]. Rashba proposed that this problem could be solved by inserting a tunneling barrier at the metal-semiconductor interface [2].Asymmetric nonmagnetic semiconductor barriers are also used in the construction of spin filters [3]. This effect is caused by the interface-induced Rashba spin-orbit coupling [4] and can be quite significant for resonant tunneling through asymmetric double-barrier structure [5].Very recently, a multichannel field-effect spin-barrier selector was investigated theoretically utilizing the Rashba and Dresselhaus effects [6]. A considerable spin polarization and an interesting "tunneling spin-galvanic" effect were found in the tunneling of electron through a single symmetric barrier utilizing the Dresselhaus effect in the barrier [7,8]. However, the off-diagonal elements in the current operator, the contribution from the Dresselhaus effect, are neglected in these works. These off-diagonal element in the currents operator could lead to the significant correction of the spin-dependent transmission, especially in a thin barrier case.In this paper, we investigate theoretically the spin-dependent tunneling through a single symmetric barrier. The barrier and contacts consist of a zinc-blende-structure semiconductor lacking the inversion symmetry. It is shown that the spin-dependent tunneling and the electric current in the plane of the interfaces are different from the previous studies [7]. This difference is significant in thin barrier case and disappears gradually with increasing the thickness of the barrier. It is interesting to notice that the spin polarization and the interface current j are enhanced by including the Dresselhaus effect in the contact regions.We consider the transmission of an electron with initial wave vector k = (k , k z ) through a flat potential barrier of height V grown...

We investigate theoretically spin-polarized transport in a one-dimensional waveguide structure under spatially periodic electric fields. Strong spin-polarized current can be obtained by tuning the external electric fields. It is interesting to find that the spin-dependent transmissions exhibit gaps at various electron momenta and/or gate lengths, and the gap width increases with increasing the strength of the Rashba effect. The strong spin-polarized current arises from the different transmission gaps of the spin-up and spin-down electrons.