Quantum Phase Transition in a Resonant Level Coupled to Interacting Leads

TL;DR

This study demonstrates a quantum phase transition in a resonant level coupled to interacting leads, revealing perfect transparency and zero-width resonance due to many-body effects in a controllable system, advancing understanding of quantum critical phenomena.

Contribution

First experimental observation of a quantum phase transition in a resonant level system coupled to Luttinger liquids with controllable parameters.

Findings

Perfect transparency of the resonant level observed.

Resonance width tends to zero at the transition.

System emulates tunneling in Luttinger liquids with tunable interactions.

Abstract

An interacting one-dimensional electron system, the Luttinger liquid, is distinct from the "conventional" Fermi liquids formed by interacting electrons in two and three dimensions. Some of its most spectacular properties are revealed in the process of electron tunneling: as a function of the applied bias or temperature the tunneling current demonstrates a non-trivial power-law suppression. Here, we create a system which emulates tunneling in a Luttinger liquid, by controlling the interaction of the tunneling electron with its environment. We further replace a single tunneling barrier with a double-barrier resonant level structure and investigate resonant tunneling between Luttinger liquids. For the first time, we observe perfect transparency of the resonant level embedded in the interacting environment, while the width of the resonance tends to zero. We argue that this unique behavior results from many-body physics of interacting electrons and signals the presence of a quantum phase transition (QPT). In our samples many parameters, including the interaction strength, can be precisely controlled; thus, we have created an attractive model system for studying quantum critical phenomena in general. Our work therefore has broadly reaching implications for understanding QPTs in more complex systems, such as cold atoms and strongly correlated bulk materials.