arXiv subjects

D. Goldhaber-Gordon

Publications and source records attributed to D. Goldhaber-Gordon.

46 records · Page 3Linked to original sources

arXiv2005

Conductance Fluctuations and Spin Symmetries in Quantum Dots

Conductance fluctuations in GaAs quantum dots with spin-orbit and Zeeman coupling are investigated experimentally and compared to a random matrix theory formulation that defines a number of regimes of spin symmetry depending on experimental parameters. Accounting for orbital coupling of the in-plane magnetic field, which can break time-reversal symmetry, yields excellent overall agreement between experiment and theory.

cond-mat.mes-hall↗

arXiv2004

Measurements of Kondo and spin splitting in single-electron transistors

We measure the spin splitting in a magnetic field $B$ of localized states in single-electron transistors using a new method, inelastic spin-flip cotunneling. Because it involves only internal excitations, this technique gives the most precise value of the Zeeman energy $Δ= \ZeemanE$. In the same devices we also measure the splitting with $B$ of the Kondo peak in differential conductance. The Kondo splitting appears only above a threshold field as predicted by theory. However, the magnitude of the Kondo splitting at high fields exceeds $2 \ZeemanE$ in disagreement with theory.

cond-mat.mes-hall↗

arXiv2003

Gate-Controlled Spin-Orbit Quantum Interference Effects in Lateral Transport

In situ control of spin-orbit coupling in coherent transport using a clean GaAs/AlGaAs 2DEG is realized, leading to a gate-tunable crossover from weak localization to antilocalization. The necessary theory of 2D magnetotransport in the presence of spin-orbit coupling beyond the diffusive approximation is developed and used to analyze experimental data. With this theory the Rashba contribution and linear and cubic Dresselhaus contributions to spin-orbit coupling are separately estimated, allowing the angular dependence of spin-orbit precession to be extracted at various gate voltages.

cond-mat.mes-hall↗

arXiv2002

Singlet-triplet transition in a single-electron transistor at zero magnetic field

We report sharp peaks in the differential conductance of a single-electron transistor (SET) at low temperature, for gate voltages at which charge fluctuations are suppressed. For odd numbers of electrons we observe the expected Kondo peak at zero bias. For even numbers of electrons we generally observe Kondo-like features corresponding to excited states. For the latter, the excitation energy often decreases with gate voltage until a new zero-bias Kondo peak results. We ascribe this behavior to a singlet-triplet transition in zero magnetic field driven by the change of shape of the potential that confines the electrons in the SET.

cond-mat.mes-hall↗

arXiv2002

The Low-Temperature Fate of the 0.7 Structure in a Point Contact: A Kondo-like Correlated State in an Open System

Besides the usual conductance plateaus at multiples of 2e2/h, quantum point contacts typically show an extra plateau at ~ 0.7(2e2/h), believed to arise from electron-electron interactions that prohibit the two spin channels from being simultaneously occupied. We present evidence that the disappearance of the 0.7 structure at very low temperature signals the formation of a Kondo-like correlated spin state. Evidence includes a zero-bias conductance peak that splits in a parallel field, scaling of conductance to a modified Kondo form, and consistency between peak width and the Kondo temperature.

cond-mat.mes-hall↗

arXiv2001

Temperature dependence of Fano line shapes in a weakly coupled single-electron transistor

We report the temperature dependence of the zero-bias conductance of a single-electron transistor in the regime of weak coupling between the quantum dot and the leads. The Fano line shape, convoluted with thermal broadening, provides a good fit to the observed asymmetric Coulomb charging peaks. However, the width of the peaks increases more rapidly than expected from the thermal broadening of the Fermi distribution in a temperature range for which Fano interference is unaffected. The intrinsic width of the resonance extracted from the fits increases approximately quadratically with temperature. Above about 600 mK the asymmetry of the peaks decreases, suggesting that phase coherence necessary for Fano interference is reduced with increasing temperature.

cond-mat.mes-hall↗

arXiv1999

Fano Resonances in Electronic Transport through a Single Electron Transistor

We have observed asymmetric Fano resonances in the conductance of a single electron transistor resulting from interference between a resonant and a nonresonant path through the system. The resonant component shows all the features typical of quantum dots, but the origin of the non-resonant path is unclear. A unique feature of this experimental system, compared to others that show Fano line shapes, is that changing the voltages on various gates allows one to alter the interference between the two paths.

cond-mat.mes-hall↗

arXiv1998

From the Kondo Regime to the Mixed-Valence Regime in a Single-Electron Transistor

We demonstrate that the conductance through a single-electron transistor at low temperature is in quantitative agreement with predictions of the equilibrium Anderson model. When an unpaired electron is localized within the transistor, the Kondo effect is observed. Tuning the unpaired electron's energy toward the Fermi level in nearby leads produces a cross-over between the Kondo and mixed-valence regimes of the Anderson model.

cond-mat.mes-hall↗

arXiv1997

Kondo Physics in a Single Electron Transistor

The question of how localized electrons interact with delocalized electrons is central to many problems at the forefront of solid state physics. The simplest example is the Kondo phenomenon, which occurs when an impurity atom with an unpaired electron is placed in a metal, and the energy of the unpaired electron is far below the Fermi energy. At low temperatures a spin singlet state is formed between the unpaired localized electron and delocalized electrons at the Fermi energy. The confined droplet of electrons interacting with the leads of a single electron transistor (SET) is closely analogous to an impurity atom interacting with the delocalized electrons in a metal. (Meir, Wingreen and Lee, 1993) We report here measurements on a new generation of SETs that display all the aspects of the Kondo phenomenon: the spin singlet forms and causes an enhancement of the zero-bias conductance when the number of electrons on the artificial atom is odd but not when it is even. The singlet is altered by applying a voltage or magnetic field or by increasing the temperature, all in ways that agree with predictions. (Wingreen and Meir 1994)

cond-mat.str-el↗

arXiv1995

Magnetic Field Dependence of the Level Spacing of a Small Electron Droplet

The temperature dependence of conductance resonances is used to measure the evolution with the magnetic field of the average level spacing $Δε$ of a droplet containing $\sim 30$ electrons created by lateral confinement of a two-dimensional electron gas in GaAs. $Δε$ becomes very small ($< 30μ$eV) near two critical magnetic fields at which the symmetry of the droplet changes and these decreases of $Δε$ are predicted by Hartree-Fock (HF) for charge excitations. Between the two critical fields, however, the largest measured $Δε= 100μ$eV is an order of magnitude smaller than predicted by HF but comparable to the Zeeman splitting at this field, which suggests that the spin degrees of freedom are important. PACS: 73.20.Dx, 73.20.Mf

cond-mat↗