No abstract

The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of experimental effort, the value of G remains the least precisely known of the fundamental constants. A discrepancy of up to 0.05 per cent in recent determinations of G suggests that there may be undiscovered systematic errors in the various existing methods. One way to resolve this issue is to measure G using a number of methods that are unlikely to involve the same systematic effects. Here we report two independent determinations of G using torsion pendulum experiments with the time-of-swing method and the angular-acceleration-feedback method. We obtain G values of 6.674184 × 10 and 6.674484 × 10 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively. These values have the smallest uncertainties reported until now, and both agree with the latest recommended value within two standard deviations.

Two-terminal selectors with high nonlinearity, based on bidirectional threshold switching (TS) behaviors, are considered as a crucial element of crossbar integration for emerging nonvolatile memory and neuromorphic network. Although great efforts have been made to obtain various selectors, existing selectors cannot fully satisfy the rigorous standard of assorted memristive elements and it is in great demand to enhance the performance. Here, a new type of Ag/TaO x /TaO y /TaO x /Ag (x < y) selector based on homogeneous trilayered oxides is developed to attain the required parameters including bidirectional TS operation, a large selectivity of ≈10 10 , a high compliance current up to 1 mA, and ultralow switching voltages under 0.2 V. Tunable operation voltages can be realized by modulating the thickness of inserted TaO y . All-TaO x -based integrated 1S1R (one selector and one memristor) cells, prepared completely by magnetron sputtering and no need of a middle electrode, exhibit a nonlinear feature, which is quite characteristic for the crossbar devices, avoiding undesired crosstalk current issues. The tantalum-oxidebased homojunctions offer high insulation, low ion mobility, and rich interfaces, which is responsible for the modulation of Ag conductive filaments and corresponding high-performance cation-based selector. These findings might advance practical implementation of two-terminal selectors in emerging memories, especially resistive random access memories.tile memory and neuromorphic computing applications. [1] These applications are generally based on the crossbar array structure, where crosstalk current issues notoriously impede the read-write operations. [2] A great deal of efforts have been made to address the critical issue, and the two-terminal selector stands out for their simple structure and no need to compromise the scalability from numerous solutions. [3] Figure 1a illustrates the configuration of 1S1R (one selector and one memristor) integrated crossbar arrays. Recently, various selector elements have been introduced, including Schottky diodes, [4] metal-insulator transition, [5] fieldassisted superlinear threshold, [6] mixedionic-electronic conduction, [7] thermionic/ tunneling emission, [8] and electrochemical-metallization-based (ECM) threshold switching (TS). [9] One Schottky diode cascaded with one memristor (namely, 1D1R) is confined only to unipolar RRAM due to the unilateral conductivity of diodes. Selectors based on transport of ions and electrons are applicable to both unipolar and bipolar RRAM, but the gradually varied voltage-current (I-V) curves predestinates the moderate nonlinearity, [3b] which is not sufficient for the application of RRAM crossbar arrays.The ECM-based selector, which is based on the formation/ diffusion and Rayleigh instability of conductive filaments Nonvolatile MemoryThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.