Rectification Coefficient Research Articles

Mechanism of interfacial thermal resistance variation in diamond/Cu/CNT tri-layer during thermal cycles

The multilayer materials in aerospace applications generally subject to thermal shock, which may significantly affect the interfacial thermal resistance (ITR) and cause serious overheating issues. Therefore, understanding the interfacial thermal transport under temperature shock is essential for effective thermal management in aerospace devices. In the present study, the variation in ITR within the diamond/Cu/carbon nanotube tri-layer after thermal cycles was investigated through non-equilibrium molecular dynamics (NEMD) simulations. We conducted four groups of investigations, exploring the impact of maximum cycle temperature, heating/cooling rates, number of cycles, and interfacial structure on ITR. The results demonstrate that while the matching degree of phonon density of states remains almost constant, the ITR varies significantly among all groups. The structural deformations and changes in lattice type can be observed in the Cu layer. Based on these findings, we proposed an “atomic distribution method” to elucidate the mechanism behind ITR variation, which was verified as applicable and precise. Additionally, the thermal rectification results demonstrate the significant effect of interfacial structure on the rectification coefficient, indicating that interfacial transport and lattice thermal conduction deserve more in-depth study in the future. This work provides a novel perspective on understanding thermal transport across the irregular and complex interfaces, which is significant for the thermal management in aerospace field.

Barbed arrow-like structure membrane with ultra-high rectification coefficient enables ultra-fast, highly-sensitive lateral-flow assay of cTnI

Acute myocardial infarction (AMI) has become a public health disease threatening public life safety due to its high mortality. The lateral-flow assay (LFA) of a typical cardiac biomarker, troponin I (cTnI), is essential for the timely warnings of AMI. However, it is a challenge to achieve an ultra-fast and highly-sensitive assay for cTnI (hs-cTnI) using current LFA, due to the limited performance of chromatographic membranes. Here, we propose a barbed arrow-like structure membrane (BAS Mem), which enables the unidirectional, fast flow and low-residual of liquid. The liquid is rectified through the forces generated by the sidewalls of the barbed arrow-like grooves. The rectification coefficient of liquid flow on BAS Mem is 14.5 (highest to date). Using BAS Mem to replace the conventional chromatographic membrane, we prepare batches of lateral-flow strips and achieve LFA of cTnI within 240 s, with a limit of detection of 1.97 ng mL−1. The lateral-flow strips exhibit a specificity of 100%, a sensitivity of 93.3% in detecting 25 samples of suspected AMI patients. The lateral-flow strips show great performance in providing reliable results for clinical diagnosis, with the potential to provide early warnings for AMI.

Spin-polarization and Coulomb interaction dependent thermal rectification in a quantum dot system

Based on the master equation approach, we investigate the thermal transport through a diode composed of a quantum dot under Coulomb interaction and tunnel-coupled to two ferromagnetic leads with antiparallel spin polarizations. We analyze the effects of spin polarizations, Coulomb interaction, mean temperature and Zeeman splitting on the thermal rectification. Firstly, we find that the thermal rectification effect is enhanced with the increase of spin polarization, because the mirror-symmetry of the system is broken by the anti-parallel spin polarization. Especially, when both leads are fully spin polarized, the asymmetry of the heat transferred by Coulomb interaction under the opposite temperature bias leads to the appearance of perfect thermal rectification and negative differential thermal conductance. Secondly, we find whether the system is in a Coulomb blockade state greatly affects the thermal rectification coefficient. As the average temperature increases or the intradot Coulomb interaction decreases, the system gradually escapes from the Coulomb blockade state, resulting in a reversal of the thermal rectification direction and ultimately leading to an increase in the rectification coefficient. Thirdly, we also find that the Zeeman splitting can be utilized to modulate the behavior of thermal rectification. Thermal rectification occurs only when Zeeman splitting and spin polarization coexist, and under different spin polarizations, the rectification coefficient exhibits different trends with the change of Zeeman splitting. These observations indicate that this structure holds potential application at a thermal rectifier as well as a thermal detector of magnetic fields.

Quasiparticles-mediated thermal diode effect in Weyl Josephson junctions

We theoretically show quasiparticles-driven thermal diode effect (TDE) in an inversion symmetry-broken Weyl superconductor (WSC)-Weyl semimetal (WSM)-WSC Josephson junction. A Zeeman field perpendicular to the WSM region of the thermally-biased Weyl Josephson junction (WJJ) induces an asymmetry between the forward and reverse thermal currents, which is responsible for the TDE. Most interestingly, we show that the sign and magnitude of the thermal diode rectification coefficient is highly tunable by the superconducting phase difference and external Zeeman field, and also strongly depends on the junction length. The tunability of the rectification, particularly, the sign changing behavior associated with higher rectification enhances the potential of our WJJ thermal diode to use as functional switching components in thermal devices.

Modulation of nonlinear optical rectification, second, and third harmonic generation coefficients in n-type quadruple δ-doped GaAs quantum wells under external fields

The paper theoretically explores the variations in nonlinear optical rectification (NOR), second (SHG), and third harmonic generation (THG) coefficients of an n-type quadruple δ-doped GaAs quantum well in the presence of electric, magnetic, and THz laser fields. The energies of subbands and associated wave functions are derived through the solution of the Schrödinger equation, utilizing effective mass and parabolic band approximations. The findings indicate that the applied external electric and magnetic fields significantly influence both the magnitudes and the positions of the peaks in NOR, SHG, and THG concerning the incident photon energies. In addition to the influences of electric and magnetic fields, subjecting the system to an intense laser field results in noticeable changes in the THG, SHG, and NOR coefficients. These numerical findings regarding the optical properties of quadruple δ-doped quantum wells in the presence of external fields could offer valuable guidance for experimental studies.

Ion conduction property of track- etched conical nanopores modified by atom layer deposition method under applied pressure

In this work, single conical nanopores in Kapton films were fabricated using the etch-track and atomic layer deposition (ALD) methods. Nanopores with different tip sizes (34 nm, 123 nm, 194 nm, respectively) were used to investigate the effect of pressure on the ionic conduction rectification (ICR) of the nanopores. Results showed that the effect of pressure on the ICR of the nanopores is related to the tip size of the nanopore and the rectification coefficient of the nanopores in the electrolyte solution. When pressure was applied across the nanopore, a volumetric flow Q was engendered through the conical-shaped nanopore. Only when the tip size of the nanopore reached a certain size could the pressure-driven liquid flow eliminate the hydraulic resistance of the pore, changing the ion distribution in the nanopore and further altering the ICR of the nanopore. For nanopores with a tip size of 34 nm, the effect of pressure on ICR was almost negligible. Only when the tip size of the nanopore was greater than a certain extent did the applied pressure significantly affect the ICR. The influence of pressure on ICR was also related to the strength of the rectification coefficient of the nanopore in the electrolyte. Nanopores exhibiting smaller ion rectification coefficients were more susceptible to the effects of pressure on their ICR.

Nonlinear optical properties of tunable spherical quantum dots under like-screened Kratzer potential

Using the effective mass approximation and the iterative procedure, we study the optical rectification (OR) coefficient of a spherical quantum dot (QD) system with like-screened Kratzer potential (LSKP), taking into account the influence of the confinement potential depth, quantum size and external environment. Our results show that the magnitude of the OR coefficient is strongly dependent on the magnitude of the tunable factor, whose peak value will be red-shifted or blue-shifted. Interestingly, the limiting potential depth and temperature have opposite effects on the OR coefficient in terms of peak location and size. Therefore, it is necessary to pay more attention to the influence of internal and external parameters on nonlinear optical effects, and apply the theory to practical experiments and the manufacture of optoelectronic devices.

Giant Rectification in Strongly Interacting Driven Tilted Systems

Correlated quantum systems feature a wide range of nontrivial effects emerging from interactions between their constituent particles. In nonequilibrium scenarios, these manifest in phenomena such as many-body insulating states and anomalous scaling laws of currents of conserved quantities, crucial for applications in quantum circuit technologies. In this work, we propose a giant-rectification scheme based on the asymmetric interplay between strong particle interactions and a tilted potential, each of which induces an insulating state on its own. While for reverse bias both cooperate and induce a strengthened insulator with an exponentially suppressed current, for forward bias they compete, generating conduction resonances; this leads to a rectification coefficient of many orders of magnitude. We uncover the mechanism underlying these resonances as enhanced coherences between energy eigenstates occurring at avoided crossings in the bulk energy spectrum of the system. Furthermore, we demonstrate the complexity of the many-body nonequilibrium conducting state through the emergence of enhanced density-matrix impurity and operator-space entanglement entropy close to the resonances. Our proposal paves the way for implementing a perfect diode in currently available electronic and quantum simulation platforms. Published by the American Physical Society 2024

Phonon transport across GaAs/Ge heterojunctions by nonequilibrium molecular dynamics

Interfaces are ubiquitous in modern electronics and assessing their properties is crucial when it comes to device reliability. Here, we present nonequilibrium molecular dynamics calculations of heat transport across GaAs/Ge heterojunctions. We compute the thermal boundary resistance, considering different interface morphologies, ranging from atomically flat to gradual or rough interfaces. We also discuss the implications for thermal rectification and predict a rectification coefficient as large as 30%.

Thermodynamics of hybrid quantum rotor devices.

We investigate the thermodynamics of a hybrid quantum device consisting of two qubits collectively interacting with a quantum rotor and coupled dissipatively to two equilibrium reservoirs at different temperatures. By modeling the dynamics and the resulting steady state of the system using a collision model, we identify the functioning of the device as a thermal engine, a refrigerator, or an accelerator. In addition, we also look into the device's capacity to operate as a heat rectifier and optimize both the rectification coefficient and the heat flow simultaneously. Drawing an analogy to heat rectification and since we are interested in the conversion of energy into the rotor's kinetic energy, we introduce the concept of angular momentum rectification, which may be employed to control work extraction through an external load.

The anisotropic transport properties of the three-terminal ballistic junction based on α−T 3 lattice

The three-terminal ballistic junction (TBJ) has promising applications in nanoelectronics. We investigate the transport properties of a α−T 3-based TBJ, where two typical configurations are considered, i.e. the A- and Z-TBJ. It is found that both A- and Z-TBJ exhibit transmission anisotropy, and the transmission of the A-TBJ has stronger anisotropy than that of the Z-TBJ. The amplitude of the rectification coefficient is smaller than that of phosphorene TBJ, but larger than that of graphene TBJ. When the symmetrical input is applied, the output voltage curve exhibits symmetric behavior. While in the case of asymmetric input, the symmetric behavior is broken, and the maximum value of the output voltage can reach a positive value. Interestingly, the voltage output shows a dramatic nonlinear response which may be useful for the voltage diode application with a push-pull input voltage. In addition, the heat fluxes of the asymmetric input are much smaller than those of the symmetric input. The maximum value of the heat flux under the symmetric input exceeds twice of that under the asymmetric input. Our results are useful to design nanoelectronic devices based on α−T 3 TBJ.

Gate-tunable giant superconducting nonreciprocal transport in few-layer Td−MoTe2

We demonstrate gate-tunable giant field-dependent nonreciprocal transport (magnetochiral anisotropy) in a noncentrosymmetric superconductor Td−MoTe2 in the thin limit. Giant magnetochiral anisotropy (MCA) with a rectification coefficient (or a figure of merit) γ=3.1×106T−1A−1 is observed at 230 mK, below the superconducting transition temperature (Tc). This is one of the largest values reported so far and may be attributed to the reduced symmetry of the crystal structure. The temperature dependence of γ indicates that ratchetlike motion of magnetic vortices is the origin of the MCA, as supported by our theoretical model. For bilayer (2 L) Td−MoTe2, we can successfully modulate γ by gating. Our experimental results provide a new route to realizing electrically controllable superconducting rectification devices in a single material. Published by the American Physical Society 2024

INVESTIGATION OF THE INFLUENCE OF SILICON NANOWIRE SYNTHESIS PARAMETERS ON THE CHARACTERISTICS OF PHOTOSENSITIVE SENSORS

Problem. Photosensitive sensors are widely used both in everyday life in climate systems and in communication devices and street lighting. In order to improve the performance parameters of photosensitive sensors, the use of silicon nanowires (SiNWs) has been proposed. A large number of articles are dedicated to the influence of synthesis parameters on the dimensions of SiNWs. However, there is a lack of research on the impact of the surface morphology of SiNW arrays on the electrical and photosensitive parameters of sensors based on them.The purpose of the work The aim of this work is to synthesize silicon nanowires using the metal-assisted chemical etching method, investigate their surface morphology, and fabricate photodiodes based on them to examine the influence of SiNW synthesis parameters on the characteristics of photosensitive sensors, considering the peculiarities of their structure.Research results. Photosensitive sensors of diode type based on SiNWs were synthesized and investigated. The influence of the following synthesis parameters of SiNWs on their lateral and vertical morphology as well as on characteristics of diode sensors based on them was demonstrated: the duration of the first and second stages of metal-assisted chemical etching (MACE), the content of silver nitride and hydrogen peroxide in the solutions of the first and second stages of MACE, as well as surface texturing and processing in isotropic and anisotropic etchants. The maximum operational parameters of the obtained photosensitivity sensors based on the SiNW array were as follows: rectification coefficient of 1320 and photosensitivity coefficient of 3.1 mA/lmV.Conclusions. The obtained results indicate that the technological parameters of the first and second stages of MACE, as well as pre- and post- chemical treatments, have a significant influence on increasing of the surface roughness, height, and porosity of SiNWs, which in turn affect the electric and photosensitive parameters of the sensors. Optimal SiNWs synthesis parameters for achieving of maximum photosensitivity have been established.

High harmonic generations triggered by the intense laser field in GaAs/AlxGa1-xAs honeycomb quantum well wires

Under constant electric and magnetic fields, the potential profile of the honeycomb quantum well wire (HQWW) is studied for varying intense laser fields to trigger and optimize high harmonics (nonlinear optical rectification, second and third harmonic generation coefficients). The finite element method has been used to simulate wavefunctions and their corresponding energy levels under effective mass approximation. We have shown that an intense laser field reshapes the potential profile of the HQWW, and this results in maximum and minimum for dipole moment matrix elements and energy differences. The increase and decrease of energy differences create blue and red shifts in the optical spectrum. In the end, we have calculated nonlinear optical rectification as 11.1x10−5 m/V. The second harmonic generation coefficient is found as 18.4x10−7 m/V which is three times and a lot bigger than bulk GaAs and GaAs/AlGaAs superlattice. The third harmonic generation coefficient is calculated as 6.2x10−15 m2/V2. As a conclusion, we have shown that HQWW can be used in harmonic generation-based optical devices.

Nonlinear optical rectification of GaAs/GaAlAs quantum dot under tangent square potential

We have investigated in detail the effects of the depth and range of the limiting potential, the quantum size parameter, temperature and hydrostatic pressure on the nonlinear optical rectification (NOR) coefficient in GaAs/GaAlAs parabolic quantum dots (QDs) with a tangent square potential. Firstly, we add the tangent-square potential of the system along the z-axis to the original parabolic QD, and then the corresponding Schrödinger equation of the modified system can be solved to find the analytical forms of different splitting energy levels and envelope wave functions. Finally, the analysis and conclusions of the numerical simulations indicate that the above parameters have significant effects on the nonlinear optical properties of the modified system.

Tunable Heat-Flux Rectification in Graded Nanowires in Non-Linear Guyer-Krumhansl Regime.

We study heat rectification in composition-graded nanowires, with nonlocal and nonlinear effects taken into account in a generalized Guyer-Krumhansl equation. Using a thermal conductivity dependent on composition and temperature, the heat equation is solved. Introducing a non-vanishing heat supply (as for instance, a lateral radiative heat supply), we explore the conditions under which either nonlocal or nonlinear effects or both contribute to heat rectification and how they may be controlled by means of the external radiative flux. The corresponding rectification coefficients are calculated as well, and the physical conditions under which the system becomes a thermal diode are pointed out.

Asymmetric thermal rectifier with designed in-plane temperature gradient zones for thermoelectric generator

Temperature difference and its duration are two main factors that affect thermoelectric performance. One can obtain the desired temperature distributions by manipulating heat flow directions; however, it is generally neglected when designing thermoelectric generators (TEGs). In this study, thermal rectifiers work in forward directions to produce in-plane temperature differences (ΔTh), where hot and cold zones are, respectively, provided by the small terminals of rectifiers and gaps between these areas. Thermoelectric legs placed above are arranged in an “X”-shape, keep TEGs' internal resistances, and have a stable range from 0.7 to 2 Ω; even heating temperatures Th have a significant range from 30 to 80 °C. When the rectification coefficient of thermal rectifiers was 1.63 and the thickness of thermoelectric legs decreased from 1 mm to 10 μm, simulated-ΔTh in the steady state rises from 2.62 to 27.10 °C rather than falling. An experimental thermal rectifier with a PI film thickness of 25 μm demonstrates that ΔTh can reach up to 14.7 °C, and the time duration is more than 60 s, where Th and ambient are 50 and 20 °C, respectively. The maximum output power can reach up to 92.48 μW when the temperature bias between Th and ambient increases to 65.33 °C. These novel thin-TEGs with designed in-plane temperature gradient zones by asymmetric thermal rectifiers are expected to be applied in distributed sensors, wearable devices, etc.

Effect of the secondary microcontact state induced by the all-factor thermal effect on bidirectional thermal contact performance

Contact interfaces are widespread in electronic systems, and the heat dissipation problem caused by the thermal contact resistance (TCR) has seriously affected the overall performance. Previous studies often disregarded the effect of the secondary microcontact state induced by thermal effects such as thermal stress and thermal softening on thermal contact performance, such as TCR, contact interface temperature distribution nonuniformity (CITDN), and the thermal rectification effect. Therefore, this paper proposes a thermomechanical coupled numerical model that considers the secondary microcontact state induced by all-factor thermal effects, and the effect of the thermal effect on bidirectional thermal contact performance under different temperatures, thermal expansion coefficients and constraints is revealed. Furthermore, a method to control the thermal rectification coefficient by controlling the contact gap was proposed. The results show that the influence of thermal effects on TCR and CITDN at high temperatures, with high thermal expansion coefficients and under strong constraint conditions cannot be disregarded and that the influence of temperature and thermal expansion coefficient on the strong constraint side is greater than that on the weak constraint side. The thermal rectification effect is effectively enhanced by adjusting the initial contact gap determined by the thermal expansion coefficient, elastic modulus and temperature.

Voltage-amplified heat rectification in SIS junctions

The control of thermal fluxes -- magnitude and direction, in mesoscale and nanoscale electronic circuits can be achieved by means of heat rectification using thermal diodes in two-terminal systems. The rectification coefficient $\mathcal{R}$, given by the ratio of forward and backward heat fluxes, varies with the design of the diode and the working conditions under which the system operates. A value of $\mathcal{R}\ll 1$ or $\mathcal{R}\gg 1$ is a signature of high heat rectification performance but current solutions allowing such ranges, necessitate rather complex designs. Here, we propose a simple solution: the use of a superconductor-insulator-superconductor (SIS) junction under an applied fast oscillating (THz range) voltage as the control of the heat flow direction and magnitude can be done by tuning the initial value of the superconducting phase. Our theoretical model based on the Green functions formalism and coherent transport theory, shows a possible sharp rise of the heat rectification coefficient with values up to $\mathcal{R} \approx 500$ beyond the adiabatic regime. The influence of quantum coherent effects on heat rectification in the SIS junction is highlighted.

Thermal Rectification in the Coaxial Carbon Nanotube@boron Nitride Nanotube Composite

To control and utilize thermal energy more precisely, an asymmetric thermal rectifier is designed in this paper. Through molecular dynamics calculations, it is found that the device has obvious thermal rectification phenomenon. The equivalent thermal conductivity of the device increases gradually with temperature. The thermal rectification coefficients at different temperatures are calculated, and it is found that the thermal rectification coefficients fluctuated wildly with temperature. The temperature distribution map inside the device and the fact that the thermal conductivity of the device increases with temperature indicate that the asymmetry of radial heat transfer and the interlayer coupling determine this thermal rectification property.