arXiv subjects

Shu-Xiao Li

Publications and source records attributed to Shu-Xiao Li.

7 recordsLinked to original sources

arXiv2022

Gate-Tunable Spin-Orbit Coupling in a Germanium Hole Double Quantum Dot

Hole spins confined in semiconductor quantum dot systems have gained considerable interest for their strong spin-orbit interactions (SOIs) and relatively weak hyperfine interactions. Here we experimentally demonstrate a tunable SOI in a double quantum dot in a Germanium (Ge) hut wire (HW), which could help enable fast all-electric spin manipulations while suppressing unwanted decoherence. Specifically, we measure the transport spectra in the Pauli spin blockade regime in the double quantum dot device.By adjusting the interdot tunnel coupling, we obtain an electric field tuned spin-orbit length lso = 2.0 - 48.9 nm. This tunability of the SOI could pave the way toward the realization of high-fidelity qubits in Ge HW systems.

cond-mat.mes-hall↗

arXiv2020

Kondo induced π-phase shift of microwave photons in a circuit quantum electrodynamics architecture

Mesoscopic systems constitute appealing platforms to study many-body physics with light and matter degrees of freedom. The Kondo effect refers to the screening of a spin-1/2 impurity by a cloud of conduction electrons, then forming a many-body Fermi liquid ground state. The Kondo resonance produces a phase shift in the transmitted electronic wave packet which depends on the symmetry and nature of the many-body ground state. Theoretical calculations suggest that the Kondo resonance can interact with the irradiation photon field and should give rise to a π-phase shift of the photon signal in the case where the ground state is a Fermi liquid. This π-phase shift of microwave photon is driven from the Korringa-Shiba relation of quantum impurity Fermi-liquid ground states. We report the first observation of such a π-phase shift in a graphene double quantum dot within a circuit quantum electrodynamics architecture where the microwave photons couple to the pseudo-spin or charge degrees of freedom. The observed Kondo temperature TK ~ 550 mK is in agreement with DC conductance measurements. All our results support the formation of a Kondo resonance located above the Fermi level of the electronic reservoirs and the occurrence of an SU(4) Fermi-liquid ground state. We finally study how the Kondo-photon interactions can be tuned by inter-dot electron tunnel coupling strengths. Our experimental achievements may contribute to a better understanding of many-body physics in hybrid circuit systems, and open up new applications in atomic thin materials from the light-matter interaction.

cond-mat.mes-hall↗

arXiv2016

Parametric strong mode-coupling in carbon nanotube mechanical resonators

Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes.

cond-mat.mes-hall↗

arXiv2016

Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture

We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.

cond-mat.mes-hall↗

arXiv2014

Introduction of DC line structures into a superconducting microwave 3D cavity

We report a technique that can noninvasively add multiple DC wires into a 3D superconducting microwave cavity for electronic devices that require DC electrical terminals. We studied the influence of our DC lines on the cavity performance systematically. We found that the quality factor of the cavity is reduced if any of the components of the electrical wires cross the cavity equipotential planes. Using this technique, we were able to incorporate a quantum dot (QD) device into a 3D cavity. We then controlled and measured the QD transport signal using the DC lines. We have also studied the heating effects of the QD by the microwave photons in the cavity.

cond-mat.mes-hall↗

arXiv2014

Coupling two distant double quantum dots to a microwave resonator

With recent advances in the circuit quantum electrodynamics (cQED) architecture, hybrid systems that couple nano-devices to microwave resonators have been developing rapidly. Here we report an experimental demonstration of two graphene double quantum dots (DQDs) coupled over a distance of up to 60 μm, through a microwave resonator. We jointly measure the two DQDs' coupling to the resonator, which causes a nonlinear response in the resonator reflection amplitude in the vicinity of the degeneracy points of the two DQDs. This phenomenon is explained by the Tavis-Cummings (T-C) mode. We further characterize this nonlocal coupling by measuring the correlation between the DC currents in the two DQDs. This correlation is observed to be strongly dependent on the average photon number in the resonator. Our results explore T-C physics in electronic transport, and also contribute to the study of nonlocal transport and future implementations of remote electronic entanglement.

cond-mat.mes-hall↗

arXiv2013

Symmetric reflection line resonator for semiconductor circuit quantum electrodynamics

We have designed and fabricated a half-wavelength reflection line resonator (RLR) that consists of a pair of two coupled microstrip lines on a GaAs/AlGaAs heterostructure. By changing the top gate voltage on a square of two dimensional electron gas under the resonator, a large range of the quality factors can be obtained. Energy loss in the two-dimensional electron gas can be minimized, thus realizing a versatile resonator suitable for integration with semiconductor quantum circuits.

cond-mat.mes-hall↗