154 research outputs found
Transfer Characteristics in Graphene Field-Effect Transistors with Co Contacts
Graphene field-effect transistors with Co contacts as source and drain
electrodes show anomalous distorted transfer characteristics. The anomaly
appears only in short-channel devices (shorter than approximately 3
micrometers) and originates from a contact-induced effect. Band alteration of a
graphene channel by the contacts is discussed as a possible mechanism for the
anomalous characteristics observed.Comment: 10 pages, 3 figures, Appl. Phys. Let
Logic Ciucuits Using Solution-processed Single-walled Carbon Nanotue Transistors
This letter reports on the realization of logic circuits employing
solution-processed networks of single-walled carbon nanotubes. We constructed
basic logic gates (inverter, NAND and NOR) with n- and p-type field-effect
transistors fabricated by solution-based chemical doping. Complementary
metal-oxide-semiconductor inverters exhibited voltage gains of up to 20, which
illustrates the great potential of carbon nanotube networks for printable
flexible electronics.Comment: 12 PAGES, 3 FIGURE
Observable non-gaussianity from gauge field production in slow roll inflation, and a challenging connection with magnetogenesis
In any realistic particle physics model of inflation, the inflaton can be
expected to couple to other fields. We consider a model with a dilaton-like
coupling between a U(1) gauge field and a scalar inflaton. We show that this
coupling can result in observable non-gaussianity, even in the conventional
regime where inflation is supported by a single scalar slowly rolling on a
smooth potential: the time dependent inflaton condensate leads to amplification
of the large-scale gauge field fluctuations, which can feed-back into the
scalar/tensor cosmological perturbations. In the squeezed limit, the resulting
bispectrum is close to the local one, but it shows a sizable and characteristic
quadrupolar dependence on the angle between the shorter and the larger modes in
the correlation. Observable non-gaussianity is obtained in a regime where
perturbation theory is under control. If the gauge field is identified with the
electromagnetic field, the model that we study is a realization of the
magnetogenesis idea originally proposed by Ratra, and widely studied. This
identification (which is not necessary for the non-gaussianity production) is
however problematic in light of a strong coupling problem already noted in the
literature.Comment: 28 pages, no figures. Final versio
Precise estimation of spin drift velocity and spin mobility in the absence of synthetic Rashba spin-orbit field in a Si metal-oxide-semiconductor
The discovery of built-in and synthetic Rashba fields in Si spin channels [S. Lee et al., Nat. Mater. 20, 1228 (2021)] challenged the conventional understanding of spin transport physics in semiconducting materials and forced researchers to reconsider the procedures used for estimating spin drift velocity and spin mobility. A conventional procedure for the estimation involves the detection of the Hanle-type spin precession under the application of an external magnetic field perpendicular to the plane; however, the in-plane effective magnetic fields due to the built-in Rashba fields hamper precise estimation because of the additional spin precession. In this work, we establish a precise method to estimate spin drift velocity and spin mobility, in addition to the spin lifetime and spin diffusion constant, by appropriately tuning the Rashba fields. Beyond the emblematic case of Si, the established method can be applied to other semiconductors, such as Ge and GaAs
Modulation of spin-torque ferromagnetic resonance with a nanometer-thick platinum by ionic gating
The spin Hall effect (SHE) and inverse spin Hall effect (ISHE) have played central roles in modern condensed matter physics especially in spintronics and spin-orbitronics, and much effort has been paid to fundamental and application-oriented research towards the discovery of novel spin–orbit physics and the creation of novel spintronic devices. However, studies on gate-tunability of such spintronics devices have been limited, because most of them are made of metallic materials, where the high bulk carrier densities hinder the tuning of physical properties by gating. Here, we show an experimental demonstration of the gate-tunable spin–orbit torque in Pt/Ni₈₀Fe₂₀ (Py) devices by controlling the SHE using nanometer-thick Pt with low carrier densities and ionic gating. The Gilbert damping parameter of Py and the spin-memory loss at the Pt/Py interface were modulated by ionic gating to Pt, which are compelling results for the successful tuning of spin–orbit interaction in Pt
Modulation of Hanle magnetoresistance in an ultrathin platinum film by ionic gating
Hanle magnetoresistance (HMR) is a type of magnetoresistance where interplay
of the spin Hall effect, Hanle-type spin precession, and spin-dependent
scattering at the top/bottom surfaces in a heavy metal controls the effect. In
this study, we modulate HMR in ultrathin Pt by ionic gating, where the surface
Rashba field created by a strong electric field at the interface between the
ionic gate and Pt plays the dominant role in the modulation. This finding can
facilitate investigations of gate-tunable, spin-related effects and fabrication
of spin devices.Comment: 10 pages, 3 figures (To appear in Applied Physics Express
Anomalous sign inversion of spin-orbit torque in ferromagnetic/nonmagnetic bilayer systems due to self-induced spin-orbit torque
Self-induced spin-orbit torques (SI-SOTs) in ferromagnetic (FM) layers have
been overlooked when estimating the spin Hall angle (SHA) of adjacent
nonmagnetic (NM) layers. In this work, we observe anomalous sign inversion of
the total SOT in the spin-torque ferromagnetic resonance due to the enhanced
SI-SOT, and successfully rationalize the sign inversion through a theoretical
calculation considering the SHE in both the NM and FM layers. The findings show
that using an FM layer whose SHA sign is the same as that of the NM achieves
efficient SOT-magnetization switching with the assistance of the SI-SOT. The
contribution of the SI-SOT becomes salient for a weakly conductive NM layer,
and conventional analyses that do not consider the SI-SOT can overestimate the
SHA of the NM layer by a factor of more than 150.Comment: 9 pages, 4 figure
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