Constantino A. Utreras-Diaz
From the theory of quantum $LC$ circuits with discrete charge, and {\em semiclassical} considerations, we obtain approximate energy eigenvalues, depending on the parameter $q_e^2/h$. Next, we include electrical resistance for the quantum $RLC$ circuit, obtaining a relation that strongly reminds us of the Landauer formula.
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The impact of semiconductor surface roughness on the electrical and thermal contact resistances and thermoEMF of thermoelectric material (TEM)-metal transient contact layer is studied theoretically. The distribution of hollows and humps on the rough surface is simulated by the truncated Gaussian distribution. The impact of distribution parameters on the electrical contact resistance and thermoEMF of thermoelectric material-metal contact is studied.
We demonstrate that the low-frequency resistance fluctuations, or noise, in bilayer graphene is strongly connected to its band structure, and displays a minimum when the gap between the conduction and valence band is zero. Using double-gated bilayer graphene devices we have tuned the zero gap and charge neutrality points independently, which offers a versatile mechanism to investigate the low-energy band structure, charge localization and screening properties of bilayer graphene.
A robust nanoelectromechanical switch is proposed based upon an asymmetric pendant moiety anchored to an organic backbone between two C60 fullerenes, which in turn are connected to gold electrodes. Ab initio density functional calculations are used to demonstrate that an electric field induces rotation of the pendant group, leading to a non-linear current-voltage relation. The non-linearity is strong enough to lead to negative differential resistance at modest source-drain voltages.
We report on the observation of non-metallic electrical conduction, resistive switching, and a negative temperature coefficient of resistance in cluster-assembled nanostructured gold films above the electrical percolation and in strong-coupling regime, from room to cryogenic temperatures (24K). The structure of the films is characterized by an extremely high density of randomly oriented crystalline nanodomains, separated by grain boundaries. The observed behavior can be explained by considering space charge limited conduction and Coulomb blockade phenomena highlighting the influence of the hig…
We study the ballistic transmission and the contact resistance ($R_c$) of a graphite-graphene contact in a top contact geometry from first principles. We find that the calculated $R_c$'s depend on the amount of graphene-graphite overlap, but quickly saturate for transfer lengths of the order of 20 Å. For contacts overlapping more than this transfer length, the $R_c$ can be lower than the 100 Ω$\cdot$μm mark. On the other hand, edge graphite-graphene contacts are expected to have very low contact resistance.
Using ab-initio methods we investigate the possibility of three-terminal graphene "T-junction" devices and show that these all-graphene edge contacts are energetically feasible when the 1D interface itself is free from foreign atoms. We examine the energetics of various junction structures as a function of the atomic scale geometry. Three-terminal equilibrium Green's functions are used to determine the transmission spectrum and contact resistance of the system. We find that the most symmetric structures have a significant binding energy, and we determine the contact resistances in the junction…
The paper proposes a strict diffusion theory of the electrical contact resistance of a thermoelectric superlattice (TES) - metal couple.The limits of the contact resistance for traditional thermoeletric materials with parabolic band spectrum and for superlattices described by Fivaz model are estimated.
The stochasticity of domain wall (DW) motion in magnetic nanowires has been probed by measuring slow fluctuations, or noise, in electrical resistance at small magnetic fields. By controlled injection of DWs into isolated cylindrical nanowires of nickel, we have been able to track the motion of the DWs between the electrical leads by discrete steps in the resistance. Closer inspection of the time-dependence of noise reveals a diffusive random walk of the DWs with an universal kinetic exponent. Our experiments outline a method with which electrical resistance is able to detect the kinetic state …
We investigate the diffusive electron transport in conductors with spatially inhomogeneous magnetic properties taking into account both impurity and normal scattering. It is found that the additional interface resistance that arises due to the magnetic inhomogeneity depends essentially on their spatial characteristics. The resistance is proportional to the spin flip time in the case when the magnetic properties of the conducting system vary smoothly enough along the sample. It can be used to direct experimental investigation of spin flip processes. In the opposite case, when magnetic character…
Using Electrical Impedance Spectroscopy to Separately Quantify the Effect of Strain on Nanosheet and Junction Resistance in Printed Nanosheet Networks
针对应变如何影响印刷MoS2纳米片网络电学性能的问题，本文采用交流阻抗谱分离纳米片与结点电阻，发现应变仅使结点电阻线性增加，并量化两类因素对应变系数的贡献。
Raman scattering (RS) spectra and current-voltage characteristics at room temperature were measured in six series of small samples fabricated by means of electron-beam lithography on the surface of a large size (5x5 mm) industrial monolayer graphene film. Samples were irradiated by different doses of C${}^+$ ion beam up to $10^{15}$ cm${}^{-2}$. It was observed that at the utmost degree of disorder, the Raman spectra lines disappear which is accompanied by the exponential increase of resistance and change in the current-voltage characteristics.These effects are explained by suggestion that hig…
What is the complex impedance of a fully coherent quantum resistance-capacitance (RC) circuit at GHz frequencies in which a resistor and a capacitor are connected in series? While Kirchhoff's laws predict addition of capacitor and resistor impedances, we report on observation of a different behavior. The resistance, here associated with charge relaxation, differs from the usual transport resistance given by the Landauer formula. In particular, for a single mode conductor, the charge relaxation resistance is half the resistance quantum, regardless of the transmission of the mode. The new mesosc…
An electrical study of thin $VO_{2}$ films in the vicinity of the structural phase transition at $68^{0}C$ shows (a) that the electrical resistance $R$ follows $log (R)$ $\propto$ $-T$ over the $T$-range, $20 < T < 80 ^{0}C$ covering both sides of the structural transition, and (b) a history dependent hysteresis loop in $R$ upon thermal cycling. These features are attributed here to transport through a granular network.
Three-dimensional topological insulators host surface states with linear dispersion, which manifest as a Dirac cone. Nanoscale transport measurements provide direct access to the transport properties of the Dirac cone in real space and allow the detailed investigation of charge carrier scattering. Here, we use scanning tunnelling potentiometry to analyse the resistance of different kinds of defects at the surface of a (Bi0.53Sb0.47)2Te3 topological insulator thin film. The largest localized voltage drop we find to be located at domain boundaries in the topological insulator film, with a resist…
Electrical resistance associated with the scattering of optically oriented electrons in n-GaAs
本文报道了n-GaAs中光取向电子流经样品时由中性施主自旋相关散射引起的异常磁电阻效应，并证明该效应对自旋极化符号呈偶对称，揭示了自由电子与局域电子自旋的关联。
The temperature dependent resistance $R$($T$) of polycrystalline ferromagnetic CoFeB thin films of varying thickness are analyzed considering various electrical scattering processes. We observe a resistance minimum in $R$($T$) curves below $\simeq$ 29 K, which can be explained as an effect of intergranular Coulomb interaction in a granular system. The structural and Coulomb interaction related scattering processes contribute more as the film thickness decreases implying the role of disorder and granularity. Although the magnetic contribution to the resistance is the weakest compared to these t…
This tutorial article presents a "bottom-up" view of electrical resistance starting from something really small, like a molecule, and then discussing the issues that arises as we move to bigger conductors. Remarkably, no serious quantum mechanics is needed to understand electrical conduction through something really small, except for unusual things like the Kondo effect that are seen only for a special range of parameters. This article starts with energy level diagrams (section 2), shows that the broadening that accompanies coupling limits the conductance to a maximum of q^2/h per level (secti…
In a recent article, we have advanced a semiclassical theory of quantum circuits with discrete charge and electrical resistance. In this work, we present a few elementary applications of this theory. For the zero resistance, inductive circuit, we obtain the Stark ladder energies in yet another way; and generalize earlier results by Chandia et. al, for the circuit driven by a combination d.c. plus a.c. electromotive force (emf). As a second application, we investigate the effect of electrical resistance, together with charge discreteness, in the current amplitude, and resonance conditions of a …
We have measured the magnetic field and temperature dependence of the resistivity of several micrometers long and heterogeneously thick graphite sample. The magnetoresistance results for fields applied nearly parallel to the graphene planes show both a granular superconducting behavior as well as the existence of magnetic order in the sample.
In this article we study measurement circuit effects in three-terminal electrical transport measurements arising from finite line impedances. We provide exact expressions relating the measured voltages and differential conductances to their values at the device under test, which allow for spurious voltage divider effects to be corrected. Finally, we test the implementation of these corrections with experimental measurements.
The crystal structure of bulk SrTiO$_3$(STO) transitions from cubic to tetragonal at around 105K. Recent local scanning probe measurements of LaAlO$_3$/SrTiO$_3$ (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. However, how these effects impact the electron conduction in LAO/STO devices has not been fully studied. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of struc…
Quadrupole topological insulators are a new class of topological insulators with quantized quadrupole moments, which support protected gapless corner states. The experimental demonstrations of quadrupole-topological insulators were reported in a series of artificial materials, such as photonic crystals, acoustic crystals, and electrical circuits. In all these cases, the underlying structures have discrete translational symmetry and thus are periodic. Here we experimentally realize two-dimensional aperiodic-quasicrystalline quadrupole-topological insulators by constructing them in electrical ci…
Several data sets of electrical breakdown in air of single-wall carbon nanotubes (SWNTs) on insulating substrates are collected and analyzed. A universal scaling of the Joule breakdown power with nanotube length is found, which appears independent of the insulating substrates used or their thickness. This suggests the thermal resistances at the interface between SWNT and insulator, and between SWNT and electrodes, govern heat sinking from the nanotube. Analytical models for the breakdown power scaling are presented, providing an intuitive, physical understanding of the breakdown process. The e…
Overcoming contact resistance at metal-2D semiconductor interfaces: atomically clean MoS2/Au ohmic junctions
通过超高真空下剥离的MoS2/Au结实验证明，本征界面是高度导电的欧姆接触，接触电阻高源于界面污染，并提出了力辅助层压恢复欧姆接触的方法。
Vertically aligned ZnO nanotube arrays fabricated on an ITO substrate are found to exhibit strong persistent photoconductivity (PPC) effect and electrically driven conductance switching behavior, though the latter shows a gradual decay from high conductance state to a low conductance state. Unlike the electrical switching, the PPC cannot be reset or reversed by an electrical pulse. Excitation wavelength dependent conductance measurement indicates the presence of the defect localized states (DLS) ~ 240meV above the valence band edge, in support of the hypothesis that the doubly ionization of th…
Environmental Effects and Brillouin's Paradox in Nonlinear Electrical Circuits
本文提出一种随机方法，用于计算非线性耗散器件在偏置下的电压波动全统计特性，通过电阻和电容组成的电路反馈影响电压累积量，并解决布里渊悖论以满足热力学要求。
By using the real-space Green-Kubo formalism we study numerically the electron transport properties of low-fluorinated graphene. At low temperatures the diffuse transport regime is expected to be prevalent, and we found a pronounced electron-hole asymmetry in electrical conductivity as a result of quasi-resonant scattering on the localized states. For the finite temperatures in the variable-range hopping transport regime the interpretation of numerical results leads to the appearance of local minima and maxima of the resistance near the energies of the localized states. A comparison with the e…
We present a scattering theory of the electromotive force and internal resistance of an electron pump. The characterization of the device performance in terms of only two parameters requires the assumption of incoherent multiple scattering within the circuit and complete thermalization among electrons moving in a given direction. The electromotive force is shown to be of the order of the driving frequency in natural units. In an open setup, the electromotive force adds to the voltage difference between reservoirs to drive the current, both facing a contact resistance which is absent in the cas…
We report on electrical spin injection measurements on MWNTs . We use a ferromagnetic alloy Pd$_{1-x}$Ni$_{x}$ with x $\approx$ 0.7 which allows to obtain devices with resistances as low as 5.6 $kΩ$ at 300 $K$. The yield of device resistances below 100 $kΩ$, at 300 $K$, is around 50%. We measure at 2 $K$ a hysteretic magneto-resistance due to the magnetization reversal of the ferromagnetic leads. The relative difference between the resistance in the antiparallel (AP) orientation and the parallel (P) orientation is about 2%.
We demonstrate that the electrical property of a single layer molybdenum disulfide (MoS2) can be significantly tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single layer MoS2 devices were varied up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon …
Contact resistance and current crowding are important to nanoscale electrical contacts. In this paper, we present a self-consistent model to characterize partially overlapped parallel contacts with varying specific contact resistivity along the contact length. For parallel tunneling contacts formed between contacting members separated by a thin insulating gap, we examine the local voltage-dependent variation of potential barrier height and tunneling current along the contact length, by solving the lumped circuit transmission line model (TLM) equations coupled with the tunneling current self co…
We have studied the electrical conductivity of two-dimensional nanowire networks. An analytical evaluation of the contribution of tunneling to their electrical conductivity suggests that it is proportional to the square of the wire concentration. Using computer simulation, three kinds of resistance were taken into account, viz., (i) the resistance of the wires, (ii) the wire---wire junction resistance, and (iii) the tunnel resistance between wires. We found that the percolation threshold decreased due to tunneling. However, tunneling had negligible effect on the electrical conductance of dense…
We examine the concept of universal quantized resistance in the AC regime through the fully coherent quantum RC circuit comprising a cavity (dot) capacitively coupled to a gate and connected via a single spin-polarized channel to a reservoir lead. As a result of quantum effects such as the Coulomb interaction in the cavity and global phase coherence, we show that the charge relaxation resistance $R_q$ is identical for weak and large transmissions and it changes from $h/2e^2$ to $h/e^2$ when the frequency (times $\hbar$) exceeds the level spacing of the cavity; $h$ is the Planck constant and $e…
Theory of electrical spin injection from a ferromagnetic (FM) metal into a normal (N) conductor is presented. We show that tunnel contacts (T) can dramatically increase spin injection and solve the problem of the mismatch in the conductivities of a FM metal and a semiconductor microstructure. We also present explicit expressions for the spin-valve resistance of FM-T-N- and FM-T-N-T-FM-junctions with tunnel contacts at the interfaces and show that the resistance includes both positive and negative contributions (Kapitza resistance and injection conductivity, respectively).
Progress in high-performance computing demands significant advances in memory technology. Among novel memory technologies that promise efficient device operation on a sub-ns timescale, resistance switching between charge ordered phases of the 1T-TaS$_2$ has shown to be potentially useful for the development of high-speed, energy efficient non-volatile memory device. While ultrafast switching was previously reported with optical pulses, determination of the intrinsic speed limits of actual devices that are triggered by electrical pulses is technically challenging and hitherto still largely unex…
Electrical switching has been observed in carefully designed metal-insulator-metal devices built at small geometries. These devices are also commonly known as memristors and consist of specific materials such as transition metal oxides, chalcogenides, perovskites, oxides with valence defects, or a combination of an inert and an electrochemically active electrode. No simple physical device has been reported to exhibit electrical switching. We have discovered that a simple point-contact or a granular arrangement formed of metal pieces exhibits bipolar switching. These devices, referred to as coh…
Nonlinear electrical properties, such as negative differential resistance (NDR), are essential in numerous electrical circuits, including memristors. Several physical origins have been proposed to lead to the NDR phenomena in semiconductor devices in the last more than half a century. Here, we report NDR behavior formation in randomly oriented graphene-like nanostructures up to 37 K and high on-current density up to 10^5 A/cm^2. Our modeling of the current-voltage characteristics, including the self-heating effects, suggests that strong temperature dependence of the low-bias resistance is resp…
It was aimed to determine whether plasma processing could contribute to enhanced capacitance and energy density of activated carbon electrode based electrochemical capacitors, through the formation of additional surface charges. While an increase of up to 35% of the gravimetric capacitance, along with ~ 20% decrease in resistance, was obtained through optimal plasma processing, increased plasma exposure yielded a drastic reduction (/increase) in the capacitance (/resistance). It was also found that the capacitance and resistance modulation was a sensitive function of sample processing as well …
Multilayer graphene (MLG) thin films are deposited on silicon oxide substrates by mechanical exfoliation (or 'scotch-tape method') from Kish graphite. The thickness and number of layers are determined from both Atomic Force Microscopy (AFM) and Raman Spectroscopy. Electrical terminals are deposited on MLGs in a four-probe configuration by electron-beam lithography, gold/titanium thermal evaporation, and lift-off. The electrical resistance is measured from room temperature down to 2 K. The electrical resistance of the MLGs shows an increase with decreasing temperature, and then decreases after …
Custodial symmetries are common in the Standard Model of particle physics. They arise when quantum corrections to a parameter are proportional to the parameter itself. Here, we show that a custodial symmetry of the chiral type is also present in a classical Su-Schrieffer-Heeger (SSH) electrical circuit with memory (memcircuit). In the absence of memory, the SSH circuit supports a symmetry-protected topological edge state. Memory induces nonlinearities that break chiral symmetry explicitly and spreads the state across the circuit. However, the resulting state is still protected against perturba…
We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor--insulator--normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.
Recent studies demonstrate that an individual magnetic domain wall (DW) can be trapped and reproducibly positioned within multiterminal (Ga,Mn)As microdevices. The electrical resistance obtained from such measurements is found to be measurably altered by the presence of this single entity. To elucidate these observations we develop a simple model for the electrical potential distribution along a multiterminal device in the presence of a single DW. This is employed to calculate the effect of a single DW upon the longitudinal and transverse resistance. The model provides very good agreement with…
Observation of Impurity-Induced Scale-Free Localization in a Disordered Non-Hermitian Electrical Circuit
该研究在含单个非厄米杂质与非互易跃迁的无序非厄米电路中，实验观测到与体态跃迁方向相反的本征态反常无标度聚集，为探索非厄米电路反常趋肤效应提供了实验基础。
The recent design of a nanoscale device with a memristive characteristic has had a great impact in nonlinear circuit theory. Such a device, whose existence was predicted by Leon Chua in 1971, is governed by a charge-dependent voltage-current relation of the form $v=M(q)i$. In this paper we show that allowing for a fully nonlinear characteristic $v=η(q, i)$ in memristive devices provides a general framework for modeling and analyzing a very broad family of electrical and electronic circuits; Chua's memristors are particular instances in which $η(q,i)$ is linear in $i$. We examine several dynami…
Topological Edge State Nucleation in Frequency Space and its Realization with Floquet Electrical Circuits
本研究构建Floquet驱动电容电路网络，利用运动方程揭示的频率空间势垒边界，通过Su-Shrieffer-Heeger Floquet晶格模型实验验证了拓扑边缘态可在频率边界处成核，为频域拓扑物态研究提供了电路实现方案。
Until recently, the accepted paradigm was that the Ohmic electrical response of nanochannel-microchannel systems is determined solely by the nanochannel while the effects of the adjacent microchannels are negligible. Two, almost identical, models were suggested to rationalize experimental observations that appeared to confirm the paradigm. However, recent works have challenged this paradigm and shown that the microchannels contribute in a non-negligible manner, and thus these two models are inadequate in describing realistic nanochannel-microchannel systems. Two newer nanochannel-microchannel …
We present a tutorial on the properties of the new ideal circuit element, a memristor. By definition, a memristor M relates the charge q and the magnetic flux $ϕ$ in a circuit, and complements a resistor R, a capacitor C, and an inductor L as an ingredient of ideal electrical circuits. The properties of these three elements and their circuits are a part of the standard curricula. The existence of the memristor as the fourth ideal circuit element was predicted in 1971 based on symmetry arguments, but was clearly experimentally demonstrated just this year. We present the properties of a single m…
We have studied the electrical conductivity of the electron gas in parallel electric and magnetic fields directed along the plane of a parabolic quantum well (across the profile of the potential). We found a general expression for the electrical conductivity applicable for any magnitudes of the magnetic field and the degree of degeneration of the electron gas. A new mechanism of generation of the negative magnetoresistance has been revealed. It has been shown that in a parabolic quantum well with a non-degenerated electron gas the negative magnetoresistance results from spin splitting of the l…
We have designed and operated a superconducting tunnel junction circuit that behaves as a two-level atom: the ``quantronium''. An arbitrary evolution of its quantum state can be programmed with a series of microwave pulses, and a projective measurement of the state can be performed by a pulsed readout sub-circuit. The measured quality factor of quantum coherence Qphi=25000 is sufficiently high that a solid-state quantum processor based on this type of circuit can be envisioned.
There have been considerable efforts devoted to the study of topological phases in certain non-Hermitian systems that possess real eigenfrequencies in the presence of gain and loss. However, it is challenging to experimentally realize such non-Hermitian topological insulators in either quantum or photonic systems, due to the difficulties in introducing controlled gain and loss. On the other hand, the wide choices of active circuit components provide us with unprecedented convenience and flexibility in engineering non-Hermitian topological insulators in electrical circuits. Here, we report expe…
We describe a circuit model for a flux-driven SQUID. This is useful for developing insight into how these devices perform as active elements in parametric amplifiers. The key concept is that frequency mixing in a flux-pumped SQUID allows for the appearance of an effective negative resistance. In the three-wave, degenerate case treated here, a negative resistance appears only over a certain range of allowed input signal phase. This model readily lends itself to testable predictions of more complicated circuits.
We propose the non-accelerator non-low-temperature simulator of quantum-field effects which is based on the feeder circuits with the special feedback. By means of it one can study the field models which contain fundamental concepts in the modern field theory but do not exist in nature in a separate form. Besides, several field phenomena might find technological applications by virtue of the electrical analogy.
We present a superconducting tunnel junction circuit which behaves as a controllable atom, and whose ground and first excited state form an effective spin 1/2. By applying microwave pulses, we have performed on this circuit experiments demonstrating the controlled manipulation of the spin : Rabi precession, Ramsey interferences, and spin echoes.
Stochastic theory of nonlinear electrical circuits in thermal equilibrium
本文推广了任意拓扑结构下非线性RLC电路的耗散力学理论，通过引入热化假设和涨落-耗散定理解释了Johnson噪声，并获得了乘性噪声的精确表达式，为研究量子电路退相干提供了新方法。
Ultrafast electrical control of dipolariton-based optical circuits with a few femto-joul per bit power consumption
提出利用波导激子–偶极极化激元实现GHz超快电调控的光学晶体管，以约3 fJ/bit能耗和25 μm²有源面积支撑超低功耗可重构光子电路。
We propose a realizable architecture using one-dimensional transmission line resonators to reach the strong coupling limit of cavity quantum electrodynamics in superconducting electrical circuits. The vacuum Rabi frequency for the coupling of cavity photons to quantized excitations of an adjacent electrical circuit (qubit) can easily exceed the damping rates of both the cavity and the qubit. This architecture is attractive both as a macroscopic analog of atomic physics experiments and for quantum computing and control, since it provides strong inhibition of spontaneous emission, potentially le…
Realizing efficient topological temporal pumping in electrical circuits
本研究在电路网络中利用有源电路元件实现了一种拓扑绝热泵，能够稳定持久地泵浦电压信号，并通过从边缘能带结构推导Chern数验证了系统的拓扑性质。
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