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Dear Colleagues,

Confined quantum systems embrace a wide variety of subjects, ranging from nanostructures—particularly quantum dots, quantum wires, and planar nanostructures, including graphene-based systems—to quantum systems of microscopic scale, such as quantum atomic gases.

Advances in the science of quantum nanostructures over the course of more than twenty years have been remarkable. As a result, confined nanoscale quantum systems already have an outstanding spectrum of applications in various important areas. More recently, studies of quantum phenomena in ultracold atomic gases have seen steadily growing progress and increasing interest, nontrivially involving subjects specific to many other research areas (e.g., polaron physics). Consequently, the optical properties of confined quantum systems represent a great experimental and theoretical interest for their characterization and getting a picture of intrinsic quantum states and collective excitations, which can have significance for potential practical realizations, even including such a fascinating perspective as quantum computing, where a breakthrough is still pending.

The main goal of this Special Issue is to bring together experimental and theoretical studies on the dynamic response of various classes of confined quantum systems and to encourage an interchange of ideas between specialists in different topics of this comprehensive scientific area. The scope of the Issue includes review papers and new original experimental and theoretical results.

Dr. Serghei Klimin
Guest Editor

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Keywords

Optical response
Quantum dots
Nanostructures
Quantum gases

Published Papers (3 papers)

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Research

11 pages, 421 KiB

Open AccessArticle

Optical Response of an Interacting Polaron Gas in Strongly Polar Crystals

by Serghei Klimin, Jacques Tempere, Jozef T. Devreese, Cesare Franchini and Georg Kresse

Appl. Sci. 2020, 10(6), 2059; https://doi.org/10.3390/app10062059 - 18 Mar 2020

Cited by 7 | Viewed by 2300

Abstract

Optical conductivity of an interacting polaron gas is calculated within an extended random phase approximation which takes into account mixing of collective excitations of the electron gas with longitudinal optical (LO) phonons. This mixing is important for the optical response of strongly polar crystals where the static dielectric constant is rather high, as in the case of strontium titanate. The present calculation sheds light on unexplained features of experimentally observed optical conductivity spectra in n-doped SrTiO

_{3}

. These features appear to be due to dynamic screening of the electron–electron interaction by polar optical phonons and hence do not require additional mechanisms for their explanation. Full article

(This article belongs to the Special Issue Optical Properties of Confined Quantum Systems 2020)

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11 pages, 1389 KiB

Open AccessArticle

Waiting Time Distributions of Transport through a Two-Channel Quantum System

by Weici Liu, Faqiang Wang and Ruisheng Liang

Appl. Sci. 2020, 10(5), 1772; https://doi.org/10.3390/app10051772 - 04 Mar 2020

Cited by 2 | Viewed by 1764

Abstract

In this work, the waiting time distribution (WTD) statistics of electron transport through a two-channel quantum system in a strong Coulomb blockade regime and non-interacting dots are investigated by employing a particle-number resolved master equation with the Born–Markov approximation. The results show that the phase difference between the two channels, the asymmetry of the dot-state couplings to the left and right electrodes, and Coulomb repulsion have obvious effects on the WTD statistics of the system. In a certain parameter range, the system manifests the coherent oscillatory behavior of WTDs in the strong Coulomb blockade regime, and the phase difference between the two channels is clearly reflected in the oscillation phase of the WTDs. The two-channel quantum dot (QD) system for non-interacting dots manifests nonrenewal characteristics, and the electron waiting time of the system is negatively correlated. The different phase differences between the two channels can clearly enhance the negative correlation. These results deepen our understanding of the WTD statistical properties of electron transport through a mesoscopic QD system and help pave a new path toward constructing nanostructured QD electronic devices. Full article

(This article belongs to the Special Issue Optical Properties of Confined Quantum Systems 2020)

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13 pages, 1600 KiB

Open AccessArticle

Photon Counting Statistics of a Microwave Cavity Coupled with Double Quantum Dots

by Faqiang Wang, Weici Liu, Xiaolei Wang, Zhongchao Wei, Hongyun Meng and Ruisheng Liang

Appl. Sci. 2019, 9(22), 4934; https://doi.org/10.3390/app9224934 - 16 Nov 2019

Viewed by 2112

Abstract

The statistical properties of photon emission counting, especially the waiting time distributions (WTDs) and large deviation statistics, of a cavity coupled with the system of double quantum dots (DQDs) driven by an external microwave field were investigated with the particle-number-resolved master equation. The results show that the decay rate of the WTDs of the cavity for short and long time limits can be effectively tuned by the driving external field Rabi frequency, the frequency of the cavity photon, and the detuning between the microwave driving frequency and the energy-splitting of the DQDs. The photon emission energy current will flow from the thermal reservoir to the system of the DQDs when the average photon number of the cavity in a steady state is larger than that of the thermal reservoir; otherwise, the photon emission energy current will flow in the opposite direction. This also demonstrates that the effect of the DQDs can be replaced a thermal reservoir when the rate difference of a photon absorbed and emitted by DQDs is larger than zero; otherwise, it is irreplaceable. The results deepen our understanding of the statistical properties of photon emission counting. It has a promising application in the construction of nanostructured devices of photon emission on demand and of optoelectronic devices. Full article

(This article belongs to the Special Issue Optical Properties of Confined Quantum Systems 2020)

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