Extended Data Fig. 3: Dynamical Coulomb blockade of QPC transmissions.
From: Quantum simulation of an exotic quantum critical point in a two-site charge Kondo circuit
a. Measured QPC transmissions τR, τL as a function of a source-drain bias VSD for different QPC gate voltages. The measured transmission is extracted by measuring the series conductance when in series with the inter-island QPC and opposite island-lead QPC set to fully transmit a single channel (τC,L/R = 1). The measured transmissions clearly dip at zero bias, consistent with dynamical Coulomb blockade (DCB) behavior. The high bias behavior (VSD ≈ 50μV) recovers the ‘intrinsic’ transmission of the QPC, unrenormalized by DCB. b. DCB measurements comparing the right island-lead QPC to the inter-island QPC. It is clear there is a substantial difference in the DCB-renormalization at zero bias between the two, likely due to the device geometry. c. Comparison of measuring τR through both islands (blue lines, as in a, b) and through the adjacent plunger gate PR (red lines). While typically we would expect no significant bias dependence when measuring through PR, we in fact see DCB-like behavior. d. Comparing the two measurement pathways of c at fixed source-drain bias as a function of the QPC gate voltage. The ‘through the island’ (blue) measurements have been shifted by 9mV to account for the large capacitive cross-talk effect when switching between the two different measurement pathways. That the high bias traces match well is indicative that there is indeed DCB-renormalization of the transmission when measuring through PR. Empirically, using the zero bias, ‘through the plunger gate’ measurement of the transmission (solid red line), best captures the relevant transmissions in the Kondo interactions of our system.
