arXiv subjects

M. Jung

Publications and source records attributed to M. Jung.

28 records · Page 2Linked to original sources

arXiv2012

A Radio Frequency Charge Parity Meter

We demonstrate a total charge parity measurement by detecting the radio frequency signal that is reflected by a lumped element resonator coupled to a single InAs nanowire double quantum dot. The high frequency response of the circuit is used to probe the effects of the Pauli exclusion principle at interdot charge transitions. Even parity charge transitions show a striking magnetic field dependence that is due to a singlet-triplet transition, while odd parity transitions are relatively insensitive to magnetic field. The measured response agrees well with cavity input-output theory, allowing accurate measurements of the interdot tunnel coupling and the resonator-charge coupling rate g_c/2pi ~ 17 MHz.

cond-mat.mes-hall↗

arXiv2012

Circuit Quantum Electrodynamics with a Spin Qubit

Circuit quantum electrodynamics allows spatially separated superconducting qubits to interact via a "quantum bus", enabling two-qubit entanglement and the implementation of simple quantum algorithms. We combine the circuit quantum electrodynamics architecture with spin qubits by coupling an InAs nanowire double quantum dot to a superconducting cavity. We drive single spin rotations using electric dipole spin resonance and demonstrate that photons trapped in the cavity are sensitive to single spin dynamics. The hybrid quantum system allows measurements of the spin lifetime and the observation of coherent spin rotations. Our results demonstrate that a spin-cavity coupling strength of 1 MHz is feasible.

cond-mat.mes-hall↗

arXiv2012

Radio frequency charge sensing in InAs nanowire double quantum dots

We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD) coupled to a radio frequency (rf) circuit. We measure the rf signal reflected by the resonator using homodyne detection. Clear single dot and DQD behavior are observed in the resonator response. rf-reflectometry allows measurements of the DQD charge stability diagram in the few-electron regime even when the dc current through the device is too small to be measured. For a signal-to-noise ratio of one, we estimate a minimum charge detection time of 350 microseconds at interdot charge transitions and 9 microseconds for charge transitions with the leads.

cond-mat.mes-hall↗

arXiv2012

Field Tuning the G-Factor in InAs Nanowire Double Quantum Dots

We study the effects of magnetic and electric fields on the g-factors of spins confined in a two-electron InAs nanowire double quantum dot. Spin sensitive measurements are performed by monitoring the leakage current in the Pauli blockade regime. Rotations of single spins are driven using electric-dipole spin resonance. The g-factors are extracted from the spin resonance condition as a function of the magnetic field direction, allowing determination of the full g-tensor. Electric and magnetic field tuning can be used to maximize the g-factor difference and in some cases altogether quench the EDSR response, allowing selective single spin control.

cond-mat.mes-hall↗

arXiv2009

Spin-Related Current Suppression in a Semiconductor-Quantum-Dot Spin-Diode Structure

We experimentally study the transport features of electrons in a spin-diode structure consisting of a single semiconductor quantum dot (QD) weakly coupled to one nonmagnetic (NM) and one ferromagnetic (FM) lead, in which the QD has an artificial atomic nature. A Coulomb stability diamond shows asymmetric features with respect to the polarity of the bias voltage. For the regime of two-electron tunneling, we find anomalous suppression of the current for both forward and reverse bias. We discuss possible mechanisms of the anomalous current suppression in terms of spin blockade via the QD/FM interface at the ground state of a two-electron QD.

cond-mat.mes-hall↗

arXiv2009

Sequential Flavour Symmetry Breaking

The gauge sector of the Standard Model (SM) exhibits a flavour symmetry which allows for independent unitary transformations of the fermion multiplets. In the SM the flavour symmetry is broken by the Yukawa couplings to the Higgs boson, and the resulting fermion masses and mixing angles show a pronounced hierarchy. In this work we connect the observed hierarchy to a sequence of intermediate effective theories, where the flavour symmetries are broken in a step-wise fashion by vacuum expectation values of suitably constructed spurion fields. We identify the possible scenarios in the quark sector and discuss some implications of this approach.

hep-ph↗

arXiv2007

Kondo effect in a semiconductor quantum dot coupled to ferromagnetic electrodes

Using a laterally-fabricated quantum-dot (QD) spin-valve device, we experimentally study the Kondo effect in the electron transport through a semiconductor QD with an odd number of electrons (N). In a parallel magnetic configuration of the ferromagnetic electrodes, the Kondo resonance at N = 3 splits clearly without external magnetic fields. With applying magnetic fields (B), the splitting is gradually reduced, and then the Kondo effect is almost restored at B = 1.2 T. This means that, in the Kondo regime, an inverse effective magnetic field of B ~ 1.2 T can be applied to the QD in the parallel magnetic configuration of the ferromagnetic electrodes.

cond-mat.mes-hall↗

arXiv2007

Electric-field control of tunneling magnetoresistance effect in a Ni/InAs/Ni quantum-dot spin valve

We demonstrate an electric-field control of tunneling magnetoresistance (TMR) effect in a semiconductor quantum-dot (QD) spin-valve device. By using ferromagnetic Ni nano-gap electrodes, we observe the Coulomb blockade oscillations at a small bias voltage. In the vicinity of the Coulomb blockade peak, the TMR effect is significantly modulated and even its sign is switched by changing the gate voltage, where the sign of the TMR value changes at the resonant condition.

cond-mat.mes-hall↗

arXiv2007

Spin transport through a single self-assembled InAs quantum dot with ferromagnetic leads

We have fabricated a lateral double barrier magnetic tunnel junction (MTJ) which consists of a single self-assembled InAs quantum dot (QD) with ferromagnetic Co leads. The MTJ shows clear hysteretic tunnel magnetoresistance (TMR) effect, which is evidence for spin transport through a single semiconductor QD. The TMR ratio and the curve shapes are varied by changing the gate voltage.

cond-mat.mes-hall↗

arXiv2004

The XPS peak structure of condensed aromatic anhydrides and imides

Photoelectron spectra of aromatic anhydrides and imides like PTCDA (perylene-tetracarboxylic dianhydride), PTCDI (perylene-tetracarboxylic diimide), and NDCA (naphthalene-dicarboxylic anhydride) on smooth single crystal surfaces show complex double peak structures in both the O1s and the anhydride C1s range. The peak intensity ratios cannot be simply explained by different chemical states of the atoms but are strongly influenced by intense shake-up satellites. Semiempirical SDCI calculations can quantitatively reproduce the experimental spectra of multilayers, provided that not only intramolecular but also intermolecular shake-up excitations are taken into account. These calculations give further insight into the process of electronic charge transfers in large organic molecules and molecular films. A variation of the molecular structure by reducing the size of the aromatic part (NDCA instead of PTCDA) or by using different functional groups (PTCDI instead of PTCDA) leads to a reduced donor/acceptor strength and hence to drastically reduced satellite intensities.

cond-mat.mtrl-sci↗