arXiv subjects

ZhenGang Zhu

Publications and source records attributed to ZhenGang Zhu.

3 recordsLinked to original sources

arXiv2019

Bias-induced chiral current and topological blockadein triple quantum dots

We theoretically investigate the quantum transport properties of a triangular triple quantum dot (TTQD) ring connected with two reservoirs by means of analytical derivation and accurate hierarchical-equations-of-motion calculation. A bias-induced chiral current in the absence of magnetic field is firstly demonstrated, which results from that the coupling between spin gauge field and spin current in the nonequilibrium TTQD induces a scalar spin chirality that lifts the chiral degeneracy and thus the time inversion symmetry. The chiral current is proved to oscillate with bias within the Coulomb blockade regime, which opens a possibility to control the chiral spin qubit by use of purely electrical manipulations. Then, a topological blockade of the transport current due to the localization of chiral states is elucidated by spectral function analysis. Finally, as a measurable character, the magnetoelectric susceptibility in our system is found about two orders of magnitude larger than that in a typical magnetoelectric material at low temperature.

cond-mat.mes-hall↗

arXiv2017

Many-body Tunneling and Nonequilibrium Dynamics of Doublons in Strongly Correlated Quantum Dots

Quantum tunneling dominates coherent transport at low temperatures in many systems of great interest. In this work we report a many--body tunneling (MBT), by nonperturbatively solving the Anderson multi-impurity model, and identify it a fundamental tunneling process on top of the well--acknowledged sequential tunneling and cotunneling. We show that the MBT involves the dynamics of doublons in strongly correlated systems. Proportional to the numbers of dynamical doublons, the MBT can dominate the off--resonant transport in the strongly correlated regime. A $T^{3/2}$--dependence of the MBT current on temperature is uncovered and can be identified as a fingerprint of the MBT in experiments. We also prove that the MBT can support the coherent long--range tunneling of doublons, which is well consistent with recent experiments on ultracold atoms. As a fundamental physical process, the MBT is expected to play important roles in general quantum systems.

cond-mat.mes-hall↗

arXiv2017

Long-range Exchange Interaction in Triple Quantum Dots in the Kondo Regime

Long-range interactions in triple quantum dots (TQDs) in Kondo regime are investigated by accurately solving the three-impurity Anderson model. For the occupation configuration of (N1,N2,N3) = (1, 0, 1), a long-range antiferromagnetic exchange interaction (JAF) is demonstrated and induces a continuous phase transition from the separated Kondo singlet (KS) to the long-range spin singlet (LSS) state between edge dots. The expression of JAF is analytically derived and numerically verified, according to which JAF can be conveniently manipulated via gate control of the detuning energy. The long-range entanglement of Kondo clouds are proved to be quite robust at strong inter-dot coupling limit. Under equilibrium condition, it induces an unexpected peak in the spectral function of the middle dot whose singly occupied level keeps much higher than the Fermi level. Under nonequilibrium condition, higher inter-dot tunneling barrier induces an anomalous enhancement of current. These novel features can be observed in routine experiments.

cond-mat.str-el↗