Noise Correlations in a Coulomb-Blockaded Quantum Dot

Abstract

We report measurements of current noise auto-and cross-correlation in a tunable quantum dot with two or three leads. As the Coulomb blockade is lifted at finite source-drain bias, the autocorrelation evolves from super-Poissonian to sub-Poissonian in the two-lead case, and the crosscorrelation evolves from positive to negative in the three-lead case, consistent with transport through multiple levels. Cross-correlations in the three-lead dot are found to be proportional to the noise in excess of the Poissonian value in the limit of weak output tunneling.Considered individually, Coulomb repulsion and Fermi statistics both tend to smooth electron flow, thereby reducing shot noise below the uncorrelated Poissonian limit [1,2]. For similar reasons, Fermi statistics without interactions also induces a negative noise crosscorrelation in multiterminal devices [1,2,3,4]. It is therefore surprising that under certain conditions, the interplay between Fermi statistics and Coulomb interaction can lead to electron bunching, i.e., super-Poissonian auto-correlation and positive cross-correlation of electronic noise.The specific conditions under which such positive noise correlations can arise has been the subject of numerous theoretical [5,6,7,8,9,10,11,12,13,14] and experimental [14,15,16,17,18,19,20,21,22,23] [10,15,24] occurring naturally in these devices. In more controlled geometries, super-Poissonian noise has been associated with inelastic cotunneling [9] in a nanotube quantum dot [20], and with dynamical channel blockade [11,12] in GaAs/AlGaAs quantum dots in the weak-tunneling [21] and quantum Hall regimes [22]. Positive noise cross-correlation has been observed in a capacitively-coupled double dot [23] as well as in electronic beam-splitters following either an inelastic voltage probe [5,6,7,8,19] or a super-Poissonian noise source [18]. The predicted positive noise cross-correlation in a three-lead quantum dot [12] has not been reported experimentally to our knowledge.This Letter describes measurement of current noise auto-and cross-correlation in a Coulomb-blockaded quantum dot configured to have either two or three leads. As a function of gate voltage and bias, regions of superand sub-Poissonian noise, as well as positive and negative noise cross-correlation, are identified. Results are in good agreement with a multi-level sequential-tunneling model in which electron bunching arises from dynamical chan-

Connection between noise and quantum correlations in a double quantum dot

“…In our case, the current in the most interesting regime is proportional to t 2 x, where x is exponentially small in ⌬ / k B T. Since the tunneling amplitude t can, in principle, be made arbitrarily small, sequential tunneling becomes the dominant process. Recently, it was shown that noise spectroscopy deep inside the Coulomb-blockade regime is possible [23][24][25][26] and in agreement with the sequential-tunneling description.…”

Thermoelectric energy harvesting with quantum dots

“…This was motivated by a number of reasons. First of all, such three-terminal setups share a number of features with mesoscopic Coulombdrag setups that have been studied both theoretically [60,61,62,63,64,65,66] as well as experimentally [67,68,69,70,71] in the last years. Such Coulomb-drag setups consist of two nearby mesoscopic conductors such as quantum dots.…”

Spin Lifetimes in Quantum Dots from Noise Measurements

“…Petta et al A method for determining spin coherence times using electrical transport through a quantum dot in the stationary state has been suggested by Engel and Loss [6], but this method can only determine coherence times up to an upper limit that is related to the temperature of the contacts. The study of current-current correlations has emerged as a tool to detect coherence properties of quantum systems such as quantum dots [7]. In nanomechanical resonators the noise power spectrum has been used to determine the oscillator occupation number and quality factor [8,9,10].…”

“…The study of current-current correlations has emerged as a tool to detect coherence properties of quantum systems such as quantum dots [7]. In nanomechanical resonators the noise power spectrum has been used to determine the oscillator occupation number and quality factor [8,9,10].…”