Ninety eight one-dimensional channels defined using split gates fabricated on a GaAs/AlGaAs heterostructure are measured during one cooldown at 1.4 K. The devices are arranged in an array on a single chip, and individually addressed using a multiplex
ing technique. The anomalous conductance feature known as the 0.7 structure is studied using statistical techniques. The ensemble of data show that the 0.7 anomaly becomes more pronounced and occurs at lower values as the curvature of the potential barrier in the transport direction decreases. This corresponds to an increase in the effective length of the device. The 0.7 anomaly is not strongly influenced by other properties of the conductance related to density. The curvature of the potential barrier appears to be the primary factor governing the shape of the 0.7 structure at a given T and B.
The properties of conductance in one-dimensional (1D) quantum wires are statistically investigated using an array of 256 lithographically-identical split gates, fabricated on a GaAs/AlGaAs heterostructure. All the split gates are measured during a si
ngle cooldown under the same conditions. Electron many-body effects give rise to an anomalous feature in the conductance of a one-dimensional quantum wire, known as the `0.7 structure (or `0.7 anomaly). To handle the large data set, a method of automatically estimating the conductance value of the 0.7 structure is developed. Large differences are observed in the strength and value of the 0.7 structure [from $0.63$ to $0.84times (2e^2/h)$], despite the constant temperature and identical device design. Variations in the 1D potential profile are quantified by estimating the curvature of the barrier in the direction of electron transport, following a saddle-point model. The 0.7 structure appears to be highly sensitive to the specific confining potential within individual devices.
Research in the field of low-temperature electronics is limited by the small number of electrical contacts available on cryogenic set ups. This not only restricts the number of devices that can be fabricated, but also the device and circuit complexit
y. We present an on-chip multiplexing technique which significantly increases the number of devices locally measurable on a single chip, without the modification of existing fabrication or experimental set-ups. We demonstrate the operation of the multiplexer by performing electrical measurements of 256 quantum wires formed by split-gate devices using only 19 electrical contacts on a cryogenic set-up. The multiplexer allows the measurement of many devices and enables us to perform statistical analyses of various electrical features which exist in quantum wires. We use this architecture to investigate spatial variations of electrical characteristics, and reproducibility on two separate cooldowns. These statistical analyses are necessary to study device yield and manufacturability, in order for such devices to form the building blocks for the realisation of quantum integrated circuits. The multiplexer provides a scalable architecture which makes a whole series of further investigations into more complex devices possible.
We study electron transport in quasi-one-dimensional wires at relatively weak electrostatic confinements, where the Coulomb interaction distorts the ground state, leading to the bifurcation of the electronic system into two rows. Evidence of finite c
oupling between the rows, resulting in bonding and antibonding states, is observed. At high dc source-drain bias, a structure is observed at 0.5(2e^2/h) due to parallel double-row transport, along with a structure at 0.25(2e^2/h), providing further evidence of coupling between the two rows.
