Differential thermopower images as a probe of many-body effects in quantum point contacts

TL;DR

This paper introduces differential thermopower imaging combined with non-equilibrium DFT as a new method to detect and analyze many-body effects in quantum point contacts, providing energy-resolved insights into local density of states.

Contribution

The study demonstrates the use of non-equilibrium thermopower measurements to probe many-body phenomena in QPCs, revealing localized and secondary states beyond conductance measurements.

Findings

Confirmed localized states at QPC saddle points

Revealed secondary states at chemical potential intersections

Established thermopower imaging as a versatile tool for many-body effects

Abstract

Mesoscopic circuit elements such as quantum dots and quantum point contacts (QPCs) offer a uniquely controllable platform for engineering complex quantum devices, whose tunability makes them ideal for generating and investigating interacting quantum systems. However, the conductance measurements commonly employed in mesoscopics experiments are poorly suited to discerning correlated phenomena from those of single-particle origin. Here, we introduce non-equilibrium thermopower measurements as a novel approach to probing the local density of states (LDOS), offering an energy-resolved readout of many-body effects. We combine differential thermopower measurements with non-equilibrium density functional theory (DFT) to both confirm the presence of a localized state at the saddle point of a QPC and reveal secondary states that emerge wherever the reservoir chemical potential intersects the gate-induced potential barrier. These experiments establish differential thermopower imaging as a robust and general approach to exploring quantum many-body effects in mesoscopic circuits.