We propose a mechanism to substantially rectify radiative heat flow by matching thin films of metal-to-insulator transition materials and polar dielectrics in the electromagnetic near field. By leveraging the distinct scaling behaviors of the local density of states with film thickness for metals and insulators, we theoretically achieve rectification ratios over 140-a 10-fold improvement over the state of the art-with nanofilms of vanadium dioxide and cubic boron nitride in the parallel-plane geometry at experimentally feasible gap sizes (~100 nm). Our rational design offers relative ease of fabrication, flexible choice of materials, and robustness against deviations from optimal film thicknesses. We expect this work to facilitate the application of thermal diodes in solid-state thermal circuits and energy conversion devices.
Geometric diodes, which take advantage of geometric asymmetry to achieve current flow preference, are promising for THz current rectification. Previous studies relate geometric diodes' rectification to quantum coherent or ballistic transport, which is fragile and critical of the high-quality transport system. Here we propose a different physical picture and demonstrate a robust current rectification originating from the asymmetric bias induced barrier lowering, which generally applies to common semiconductors in normal environments. Key factors to the diode's performance are carefully analyzed…
Spin-diodes are usually resonant in nature (GHz frequency) and tuneable by magnetic field and bias current with performances, in terms of sensitivity and minimum detectable power, overcoming the semiconductor counterpart, i.e. Schottky diodes. Recently, spin diodes characterized by a low frequency detection (MHz frequency) have been proposed. Here, we show a strategy to design low frequency detectors based on magnetic tunnel junctions having the interfacial perpendicular anisotropy of the same order of the demagnetizing field out-of-plane component. Micromagnetic calculations show that to reac…
Similar to the diode in electronics, a thermal diode is a two-terminal device that allows heat to transfer easier in one direction (forward bias) than in the opposite direction (reverse bias). Unlike conductive and convective thermal diodes, a photonic thermal diode operates in a contactless mode and may afford a large operating temperature range. In this work, a novel near-field photonic thermal diode with hexagonal boron nitride (hBN) and indium antimonide (InSb) is proposed and theoretically demonstrated. The temperature dependence of the interband absorption of InSb is used to couple (or d…
Backward diodes conduct more efficiently in the reverse bias than in the forward bias, providing superior high frequency response, temperature stability, radiation hardness, and 1/f noise performance than a conventional diode conducting in the forward direction. Here we demonstrate a van der Waals material based backward diode by exploiting the giant staggered band offsets of WSe2/SnSe2 vertical heterojunction. The diode exhibits an ultra-high reverse rectification ratio (R) of ~2.1x10^4 and the same is maintained up to an unusually large bias of 1.5 V - outperforming existing backward diode r…
Phase change thermal diodes (PCTD) suffer from fairly low thermal rectification ratio, which hampers their widespread utilization as thermal management and control units for cutting-edge technologies, encompassing photovoltaics, thermoelectric modules, batteries and other miniaturized electronic products, etc. It is thus indispensable to explore a high-performance PCTD. Herein, a tunable and scalable PCTD is modeled, theoretically analyzed, fabricated and experimentally executed, accessing an unprecedented giant thermal rectification ratio of 3.0 at ambient temperature. With optimized length r…
Thermal rectification ratios of solid-liquid phase change thermal diodes (SL-PCTDs) are not sustainable beyond a certain temperature bias, necessitating reasonably compatible designs. Manipulating the heat transfer in the forward and reverse directions of the SL-PCTD is of great practical interest to achieve persistent performance. Herein, a SL-PCTD prototype is investigated under the supercooling effect of a phase change material (calcium chloride hexahydrate). In the forward direction, supercooling effect plays a significant role in sustaining natural convection far below the melting tempera…
Magnetic tunnel junctions (MTJs) have attracted strong research interest within the last decades due to their potential use as nonvolatile memory such as MRAM as well as for magnetic logic applications. Half-metallic magnets (HMMs) have been suggested as ideal electrode materials for MTJs to achieve an extremely large tunnel-magnetoresistance (TMR) effect. Despite their high TMR ratios, MTJs based on HMMs do not exhibit current rectification, i.e., a diode effect, which was achieved in a magnetic tunnel junction concept based on HMMs and type-II spin-gapless semiconductors (SGSs). The proposed…
In this paper, we explore the far-field radiative thermal rectification potential of common materials such as metals, dielectrics and doped semi-conductors using radiative and thermo-radiative properties extracted from literature. Ten different materials are considered. The rectification coefficient is then calculated for 44 pairs of materials; each pair can be used for the two terminals of a radiative thermal diode. A thermal bias of 200 K is considered. The choice of materials and thermal bias value is only bound by data availability in literature. Obtained results, highlight new candidate m…
We present a thermal device based on the near-field interaction between two substrates made of a polar and a metal-insulator-transition material. As a result of the temperature dependence of the optical properties, this device acts as a thermal rectifier, implying a strong asymmetry in the heat flux when reversing the two temperatures. By covering both substrates with a graphene sheet we show a significant enhancement of rectification coefficient. By investigating the flux spectral properties along with its distance dependence, we prove that this enhancement is associated to a change in the po…
Taking advantage of phase-transition and reconfigurable metamaterials, dynamic control of nanoscale thermal modulation can be achieved through the near-field radiative thermal rectification devices. In this work, an active-tuning near-field thermal rectifier using reconfigurable phase-transition metamaterials is explored. The rectifier has two terminals separated by vacuum, working under a controllable operational temperature around the critical temperature of the phase-transition material VO2. One of the terminals is a stretchable structure made of PDMS thin film and grating consisting of var…
Thermal rectification can occur when heat is transferred asymmetrically. We consider in this work, the case of a composite wall with one conductive and radiative layer. Both Rosseland and surface radiation approximations are used for taking into account radiative transfer. Analytical expressions for the rectification factor are given. It is shown that this factor is bounded by a maximum value of around 2.62.
A superconducting diode is an electronic device that conducts supercurrent and exhibits zero resistance primarily for one direction of applied current. Such a dissipationless diode is a desirable unit for constructing electronic circuits with ultralow power consumption. However, realizing a superconducting diode is fundamentally and technologically challenging, as it usually requires a material structure without a centre of inversion, which is scarce among superconducting materials. Here, we demonstrate a superconducting diode achieved in a conventional superconducting film patterned with a co…
In this paper, we aim to understand the apparent characteristics of IQE and I-V curve in AlGaInP and InGaN LED devices. For the analysis, we separate the current into radiative current and non-radiative current component by using the information of IQE. We carefully analyze each current component by ideality factor, S parameter, and the modified Shockley diode equation which is suitable for LED device. Through the analyses, it has been found that the characteristics of respective current components are basically similar for both samples while the physical origin of the potential drop induced b…
Metal-Nb$_{2}$O$_{5-x}$-metal memdiodes exhibiting rectification, hysteresis, and capacitance are demonstrated for applications in neuromorphic circuitry. These devices do not require any post-fabrication treatments such as filament creation by electroforming that would impede circuit scalability. Instead these devices operate due to Poole-Frenkel defect controlled transport where the high defect density is inherent to the Nb$_{2}$O$_{5-x}$ deposition rather than post-fabrication treatments. Temperature dependent measurements reveal that the dominant trap energy is 0.22 eV suggesting it result…
