Spin-orbit coupling (SOC) is a key interaction in spintronics, allowing an electrical control of spin or magnetization and, vice versa, a magnetic control of electrical current. However, recent advances have revealed much broader implications of SOC that is also central to the design of topological states, including topological insulators, skyrmions, and Majorana fermions, or to overcome the exclusion of two-dimensional ferro-magnetism expected from the Mermin-Wagner theorem. SOC and the resulting emergent interfacial spin-orbit fields are simply realized in junctions through structural inversion asymmetry, while the anisotropy in magnetoresistance (MR) allows for their experimental detection. Surprisingly, we demonstrate that an all-epitaxial ferromagnet/ MgO/metal junction with only a negligible MR anisotropy undergoes a remarkable transformation below the superconducting transition temperature of the metal. The superconducting junction has a three orders of magnitude higher MR anisotropy and supports the formation of spin-triplet superconductivity, crucial for superconducting spintronics, and topologically-protected quantum computing. Our findings call for revisiting the role of SOC in other systems which, even when it seems negligible in the normal state, could have a profound influence on the superconducting response.For over 150 years magnetoresistive effects have provided attractive platforms to study spin-dependent phenomena and enable key spintronic applications [1]. Primarily, spintronics relies on junctions with at least two ferromagnetic layers to provide sufficiently large magnetoresistance (MR). Record room-temperature MR and commercial applications employ junctions of common ferromagnets, such as Co and Fe with MgO tunnel barrier [2,3]. Alternatively, MR occurs in single ferromagnetic layers with an interplay of interfacial spin-orbit coupling (SOC). However, in metallic systems this phenomenon, known as the tunneling anisotropic MR (TAMR) [4], is typically < 1% and precludes practical applications. Here we show experimentally that a negligible MR in an all-epitaxial ferromagnet/MgO/metal junction is drastically enhanced below the superconducting transition temperature of the metal. We explain this peculiar behavior with the role of the interfacial SOC in the formation of spin-triplet superconductivity which can enable low-power superconducting spintronics [5-7] and topologically-protected quantum computing [8,9].

Organic molecules have recently revolutionized ways to create new spintronic devices. Despite intense studies, the statistics of tunneling electrons through organic barriers remains unclear. Here we investigate conductance and shot noise in magnetic tunnel junctions with PTCDA barriers a few nm thick. For junctions in the electron tunneling regime, with magnetoresistance ratios between 10 and 40\%, we observe superpoissonian shot noise. The Fano factor exceeds in 1.5-2 times the maximum values reported for magnetic tunnel junctions with inorganic barriers, indicating spin dependent bunching in tunneling. We explain our main findings in terms of a model which includes tunneling through a two level (or multilevel) system, originated from interfacial bonds of the PTCDA molecules. Our results suggest that interfaces play an important role in the control of shot noise when electrons tunnel through organic barriers

Subband gap photoresponse of nanocrystalline silicon in a metal-oxide-semiconductor device J. Appl. Phys.

The observation of perpendicular magnetic anisotropy (PMA) at MgO/Fe interfaces boosted the development of spintronic devices based on ultrathin ferromagnetic layers. Yet, magnetization reversal in the standard magnetic tunnel junctions (MTJs) with competing PMA and in-plane anisotropies remains unclear. Here we report on the field induced nonvolatile broken symmetry magnetization reorientation transition from the in-plane to the perpendicular (out of plane) state at temperatures below 50 K. The samples were 10 nm thick Fe in MgO/Fe(100)/MgO as stacking components of V/MgO/Fe/MgO/Fe/Co double barrier MTJs with an area of 20 × 20 μm2. Micromagnetic simulations with PMA and different second order anisotropies at the opposite Fe/MgO interfaces qualitatively reproduce the observed broken symmetry spin reorientation transition. Our findings open the possibilities to develop multistate epitaxial spintronics based on competing magnetic anisotropies.

The unique properties of spin-polarized surface or edge states in topological insulators (TIs) make these quantum coherent systems interesting from the point of view of both fundamental physics and their implementation in low power spintronic devices. Here we present such a study in TIs, through tunneling and noise spectroscopy utilizing TI/Al 2 O 3 /Co tunnel junctions with bottom TI electrodes of either Bi 2 Te 3 or Bi 2 Se 3 . We demonstrate that features related to the band structure of the TI materials show up in the tunneling conductance and even more clearly through low frequency noise measurements. The bias dependence of 1/f noise reveals peaks at specific energies corresponding to band structure features of the TI. TI tunnel junctions could thus simplify the study of the properties of such quantum coherent systems that can further lead to the manipulation of their spin-polarized properties for technological purposes. A topological insulator (TI) is a material which is insulating in the bulk but presents spin-dependent conducting edge or surface states which are protected by time-reversal symmetry.1-3 A 2D or 3D TI presents edge or surface states, respectively, which are spin-polarized in-plane, and locked at right angles to the carrier momentum, so that electrons with spin-up/down propagate in opposite directions. The edge or surface states of a TI consist of an odd number of massless Dirac cones. These properties along with their high mobility make TI materials interesting for next generation, low dissipation, and spintronic applications 4,5 in which the electron spins are manipulated even without any magnetic fields. The experimental surge regarding these materials occurred with the prediction of Bi-based TIs 6 and their posterior experimental realization.7 Bi 2 Se 3 and Bi 2 Te 3 , in particular, became the prototypical TI materials that were studied most heavily.To date, the experimental verification of the band structure of TI materials has been predominantly carried out by angle-resolved photoemission spectroscopy (ARPES), which yields energy-momentum graphs of band dispersion for probing depths of under a few nm. 7,8 Also, the use of spin-ARPES has allowed the determination of the spin dependence of the topological surface states. 9 On the other hand, the use of scanning tunneling microscope (STM) allows obtaining information regarding the local density of states (DOS) and the topography of surfaces. By the study of quasiparticle scattering with STM, bands can be mapped very close to the Fermi surface, with a considerably lower energy range and at a smaller scale than with ARPES. [10][11][12][13] Although immensely useful, these techniques are usually cumbersome and the conditions of study are far from a practical application of TIs. A versatile and relatively simple technique to determine the DOS of TI materials could be the study of electronic transport and noise through planar tunneling devices. So far, individual or heterostructure devices with TI layers have mainly dealt with lateral electro...

Transition metal dichalcogenide field-effect transistors (FETs) have been actively explored for low-power electronics, light detection, and sensing. Albeit promising, their performance is strongly limited by low-frequency noise (LFN). Here, we report on the study of LFN in MoS2 FETs on SiO2 substrates in ambient conditions using photodoping. Using this external excitation source allows us to access different non-equilibrium steady states and cross over different noise regimes. We observe a dependence of the noise power spectrum with the transient decay time window, approaching 1/f -type when the system is closer to equilibrium, and identify a dependence of the LFN with channel thickness. Monolayer/bilayer devices exhibit random telegraph noise for insulating regimes and 1/f -type Hooge mobility fluctuations (HMF) for conductive regimes. Thicker devices exhibit mainly 1/f -type carrier number fluctuations (CNF). In the latter, we observe a photodoping-induced change from a near parabolic to a near linear dependence of the inverse 1/f noise amplitude above the threshold gate voltage. This change indicates a crossover in the LFN mechanism from CNF to HMF. We demonstrate that the study of conductance and noise under photodoping is an effective tool to identify dominating carrier noise mechanisms in few-atomic-layer FETs for a wide range of doping regimes.

Single layer magnetoresistive sensors were designed in a Wheatstone bridge configuration using La 2/3 Sr 1/3 MnO3 ferromagnetic oxide thin film. Uniaxial anisotropy was induced by performing epitaxial deposition of the films on top of vicinal SrTiO3 substrate. X-ray scan confirms high crystalline quality of the films and the magnetic anisotropy was checked by Magneto-optical Kerr Effect measurements. Thanks to the anisotropic magnetoresistive effect and the very low noise measured in the devices, sub-nT resolution was achieved above 100 Hz at 310 K.

We analyze shot noise in a magnetic tunnel junction with a two-level quantum dot attached to the magnetic electrodes. The considerations are limited to the case when some transport channels are suppressed at low temperatures. Coupling of the two dot's levels to the electrodes are assumed to be generally different and also spin dependent. To calculate the shot noise we apply the approach based on the full counting statistics. The approach is used to account for experimental data obtained in magnetic tunnel junctions with organic barriers. The experimentally observed Fano factors correspond to the super-Poissonian statistics, and also depend on relative orientation of the electrodes' magnetic moments. We have also calculated the corresponding spin shot noise, which is associated with fluctuations of spin current.