Odd and even Kondo effects from emergent localisation in quantum point contacts

Abstract

A quantum point contact (QPC) is a very basic nano-electronic device: a short and narrow transport channel between two electron reservoirs. In clean channels electron transport is ballistic and the conductance $G$ is then quantised as a function of channel width with plateaus at integer multiples of $2e^2/h$ ($e$ is the electron charge and $h$ Planck's constant). This can be understood in a picture where the electron states are propagating waves, without need to account for electron-electron interactions. Quantised conductance could thus be the signature of ultimate control over nanoscale electron transport. However, even studies with the cleanest QPCs generically show significant anomalies on the quantised conductance traces and there is consensus that these result from electron many-body effects. Despite extensive experimental and theoretical studies understanding of these anomalies is an open problem. We report evidence that the many-body effects have their origin in one or more spontaneously localised states that emerge from Friedel oscillations in the QPC channel. Kondo physics will then also contribute to the formation of the many-body state with Kondo signatures that reflect the parity of the number of localised states. Evidence comes from experiments with length-tunable QPCs that show a periodic modulation of the many-body physics with Kondo signatures of alternating parity. Our results are of importance for assessing the role of QPCs in more complex hybrid devices and proposals for spintronic and quantum information applications. In addition, our results show that tunable QPCs offer a rich platform for investigating many-body effects in nanoscale systems, with the ability to probe such physics at the level of a single site.

NOTE: 59 page document. Pages 1-17 main text (with 4 figures); pages 18-45 supplementary information; pages 46-59 example of full data set

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• Magnetic impurity formation in quantum point contacts
• Many-body spin related phenomena in ultra-low-disorder quantum wires
• Local moment formation in quantum point contacts
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Cited by in corpus (40)

• All-electric all-semiconductor spin field effect transistors
• Two-terminal transport measurements with cold atoms
• Probing quantum devices with radio-frequency reflectometry
• Conductance Quantization at zero magnetic field in InSb nanowires
• Mapping out spin and particle conductances in a quantum point contact
• Breaking the entanglement barrier: Tensor network simulation of quantum transport
• Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy
• Shot Noise in Mesoscopic Systems: from Single Particles to Quantum Liquids
• Ballistic one-dimensional holes with strong g-factor anisotropy in germanium
• Kondo screening in a charge-insulating spinon metal
• Electronic magnetization of a quantum point contact measured by nuclear magnetic resonance
• Statistical study of conductance properties in one-dimensional quantum wires focussing on the 0.7 anomaly
• On the relation between the 0.7-anomaly and the Kondo effect: Geometric Crossover between a Quantum Point Contact and a Kondo Quantum Dot
• Spin fluctuations in the 0.7-anomaly in quantum point contacts
• Electron phase shift at the zero-bias anomaly of quantum point contacts
• Detection and control of spin-orbit interactions in a GaAs hole quantum point contact
• Tuning the Fano Resonance with an Intruder Continuum
• Non-universal transmission phase behaviour of a large quantum dot
• Functional Renormalization Group Approach for Inhomogeneous One-Dimensional Fermi Systems with Finite-Ranged Interactions
• Dependence of the 0.7 anomaly on the curvature of the potential barrier in quantum wires
• The effect of split gate size on the electrostatic potential and 0.7 anomaly within one-dimensional quantum wires on a modulation doped GaAs/AlGaAs heterostructure
• Thermoelectric Scanning Gate Interferometry on a Quantum Point Contact
• Magnetic Field Inducing Zeeman Splitting and Anomalous Conductance Reduction of Half-integer Quantized Plateaus in InAs Quantum Wires
• Scanning Gate Imaging of quantum point contacts and the origin of the 0.7 Anomaly
• Improving reproducibility of quantum devices with completely undoped architectures
• Signature of f-electron conductance in $\alpha$-Ce single-atom contacts
• Enhancement of Rashba spin-orbit coupling by electron-electron interaction
• Probing strain modulation in a gate-defined one dimensional electron system
• Formation mechanism of bound states in graphene point contacts
• Universal conductance dips and fractional excitations in a two-subband quantum wire
• Dynamic nuclear polarization at high Landau levels in a quantum point contact
• Detecting weak coupling in mesoscopic systems with a nonequilibrium Fano resonance
• Incipient singlet-triplet states in a hybrid mesoscopic system
• Non-linear spin filter for non-magnetic materials at zero magnetic field
• Robust recipe for low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure
• Automated in situ optimization and disorder mitigation in a quantum device
• Local Kondo temperatures in atomic chains
• The 0.7 anomaly in quantum point contact; many-body or single-electron effect?
• Steady-state dc transport through an Anderson impurity coupled to leads with spin-orbit coupling
• On-chip quantum sensing of Kondo spins in a high-mobility quasi-one-dimensional nanoconstriction