Related Experiment Video
Updated: Aug 9, 2025
10:40
High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
7.6K
Negative-mass exciton polaritons induced by dissipative light-matter coupling in an atomically thin semiconductor
M Wurdack1, T Yun2,3,4,5, M Katzer6
1ARC Centre of Excellence in Future Low-Energy Electronics Technologies and Department of Quantum Science and Technology, Research School of Physics, The Australian National University, Canberra, ACT, 2601, Australia. matthias.wurdack@anu.edu.au.
Nature Communications
|February 23, 2023
Summary
Researchers engineered exciton polaritons with negative mass using dissipative coupling in optical microcavities. This anomalous dispersion, observed in monolayer WS2, shows polaritons moving opposite to their momentum, opening new quantum matter research avenues.
Area of Science:
- Condensed matter physics
- Quantum optics
- Materials science
Background:
- Dispersion engineering controls light speed and particle dynamics, enabling phenomena like negative mass.
- Exciton polaritons, formed by coupling excitons and photons, are promising for novel quantum effects.
Purpose of the Study:
- To demonstrate negative mass in exciton polaritons via "non-Hermitian dispersion engineering."
- To investigate anomalous dispersion in atomically thin materials within optical microcavities.
Main Methods:
- Fabrication of planar microcavities with embedded monolayer WS2.
- Optical measurements to directly observe and characterize the exciton polariton dispersion.
- Analysis of the relationship between polariton momentum and propagation direction.
Main Results:
- Observation of an inverted (anomalous) dispersion for the lower polariton branch, indicating negative mass.
- Direct measurement of negative-mass exciton polaritons in WS2/microcavity systems.
- Demonstration that negative-mass polaritons propagate opposite to their momentum.
Conclusions:
- Dissipative coupling enables "non-Hermitian dispersion engineering" for exciton polaritons.
- Realization of negative-mass polaritons in solid-state systems.
- Opens new pathways for exploring novel quantum phases and exotic quasiparticle dynamics.
Related Concept Videos
01:29Potential Due to a Polarized Object
449
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
449
01:12Fermi Level Dynamics
303
The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
Electron affinity in semiconductors refers to the energy gap between the minimum of its conduction band and the vacuum level and it is a critical parameter in determining how easily a semiconductor can accept additional electrons.
The work...
303
01:20Types of Semiconductors
699
Intrinsic semiconductors are highly pure materials with no impurities. At absolute zero, these semiconductors behave as perfect insulators because all the valence electrons are bound, and the conduction band is empty, disallowing electrical conduction. The Fermi level is a concept used to describe the probability of occupancy of energy levels by electrons at thermal equilibrium. In intrinsic semiconductors, the Fermi level is positioned at the midpoint of the energy gap at absolute zero. When...
699
01:24Metal-Semiconductor Junctions
424
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The...
424
01:28Induced Electric Dipoles
4.3K
A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
4.3K
01:27Biasing of Metal-Semiconductor Junctions
300
Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
In Schottky junctions, where the semiconductor is n-type, applying a positive voltage to the metal relative to the semiconductor reduces its Fermi...
300