Quantum coherence in noise power spectrum in two quantum dots

TL;DR

This study investigates quantum interference effects in the noise power spectrum of two quantum dots, revealing how coupling strength influences current correlations and spectral features, including a quantum critical point.

Contribution

It introduces a spectral decomposition method to distinguish local currents and analyzes the impact of coupling strength on noise spectra in quantum dots.

Findings

Weak coupling shows dips at inter-level excitation frequencies.

Strong coupling results in two coherently coupled relaxators with distinct relaxation frequencies.

A quantum critical point separates two regimes with different current dynamics.

Abstract

We present studies of quantum interference in a noise power spectrum in the system of two quantum dots (2QD) in a T-geometry. Performing the spectral decomposition we are able to separate local currents and distinguish between the intra- and inter-level current correlation contributions to the noise power spectrum. In particular, we analyzed the large bias regime and show that for a weak coupling of 2QD with the electrodes the noise power spectrum has dips at frequencies characteristic to inter-level excitations. For a strong coupling the electron transport changes its nature and the dynamics of the current correlations is different: there are two coherently coupled relaxators with different relaxation frequencies. These two regimes of current dynamics are separated by a quantum critical point, in which the noise power spectrum shows a specific frequency dependence. In the linear response limit the noise power spectrum is related to the admittance, which shows characteristics different, due to quantum interference, for the weak and strong coupling case.