Tailoring exciton-photon interactions in organic semiconductor microcavities: From resonance-controlled photophysics to spontaneous coherence

定制有机半导体微腔中的激子-光子相互作用：从共振控制光物理到自发相干

• 批准号: RGPIN-2014-04530
• 负责人: Silva, Carlos
• 金额: $ 3.06万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=632989
• 关键词: Tailoring; exciton; photon; interactions; organic

If intense light irradiates solids, an exotic phase of matter called a Bose-Einstein condensate (BEC) is possible. By interacting strongly with materials, light couples with electrons to make 'half-light, half-electron' quasiparticles, termed exciton-polaritons, many of which may occupy the same quantum-mechanical state, so they all move as one, akin to a large ensemble of pairs of figure skaters, all performing in exquisite choreography when the spotlight is upon them. Individual particles lose their identity, acting cooperatively as a 'quantum liquid' over the entire solid when the laser shines on it. Such macroscopic spontaneous coherence (the collective quantum behaviour polaritons, much like the large number of figure skaters) of is at the origin of many important but poorly understood condensed-matter phenomena such as superfluidity. These states have only been observed in very specific solids called semiconductor quantum wells – built by atoms arranged in a crystal, in which electrons are confined to move in two dimensions, and at very low temperatures (~20 K, or -253 °C). I will address the following question: can we find such condensates at room temperature in solids made with molecules? This is a big question because it addresses the physics of these states in materials beyond 'simple' solids, built with organic molecules like those that surround us and are in us, in a temperature environment familiar to us. Understanding this fundamental behaviour will bring new breakthroughs in quantum mechanics by generalising the physics of formation and dissipation of this new state of matter. This may lead to new coherent light sources that consume less power than conventional lasers, and to devices that may be used in quantum computers. Molecules are configurationally 'soft and fluffy', resulting in structural disorder. Electronic interactions between molecules are therefore complex, which can be an important cause of coherence dissipation, potentially hindering condensation. Nonetheless, organic materials are ideal candidates for BEC because they absorb light very strongly, rendering the strength of the coupling between photons (light) and electrons well over an order of magnitude larger than in quantum wells, and can be stronger than energetic disorder in good optical devices. Furthermore, in organic semiconductors it is theoretically possible to form quantum condensates in these materials at room temperature, which is not generally possible with inorganic quantum wells with over an order of magnitude lower exciton binding energies. I will fabricate new devices based on plastics, which will permit the study of these fundamental physics with intricate detail because it will be possible to more easily incorporate molecular materials in them. I will study a range of materials that conduct electricity and may be used in optoelectronic devices, ranging from crystals composed of molecules to conducting plastics.I underline the potential for transformative impact of the proposed programme of work. We will use new fabrication protocols to make devices, and then study them with sophisticated experimental techniques producing short laser pulses (shorter than a millionth of a millionth of a second) to study polariton condensation processes in real time. The impact of my work will be to develop a rigorous framework to understand and control how light interacts with these materials, and real-life applications such as lasers can emerge in the long term. This grant will enable big-picture understanding of photophysics of plastic semiconductors, connecting concepts from classical polymer science, condensed-matter physics, and chemical physics.

如果强光照射固体，则可能会出现一种称为玻色-爱因斯坦凝聚（BEC）的奇异物质相，通过与材料相互作用，光与电子耦合形成“半光、半电子”准粒子，称为激子极化子。其中许多可能占据相同的量子力学状态，因此它们都作为一个整体移动，类似于一大群花样滑冰运动员，在聚光灯下都以精美的舞蹈表演当激光照射在它们身上时，单个粒子失去了它们的身份，在整个固体上协同作用（集体量子行为极化子，就像大量的花样滑冰运动员一样）。是许多重要但人们知之甚少的凝聚态物质现象（例如超流）的起源。这些状态只能在称为半导体量子阱的非常特殊的固体中观察到——由排列在晶体中的原子构成，其中电子被限制在其中移动。二维，并且在非常低的温度（~20 K，或-253 °C）下，我将解决以下问题：我们可以在室温下在由分子制成的固体中找到这种凝聚物吗？在我们熟悉的温度环境中，在“简单”固体之外的材料中研究这些状态的物理学，这些材料是由我们周围和我们体内的有机分子构成的，理解这种基本行为将通过概括量子力学的物理学带来新的突破。的形成和消散这种新的物质状态可能会产生比传统激光器消耗更少能量的新相干光源，并且可能会导致量子计算机中使用的分子结构“柔软而蓬松”，从而导致结构之间的电子相互作用。因此，分子很复杂，这可能是相干耗散的一个重要原因，可能会阻碍凝聚。然而，有机材料是 BEC 的理想候选者，因为它们吸收光的能力非常强，使得光子（光）和电子之间的耦合强度远远超过。比量子阱大一个数量级，并且比良好光学器件中的能量无序更强。此外，在有机半导体中，理论上可以在室温下在这些材料中形成量子凝聚体，这对于无机量子来说通常是不可能的。我将制造基于塑料的新器件，这将允许对这些基础物理进行复杂的细节研究，因为我将可以更容易地将分子材料融入其中。一系列材料导电，可用于光电设备，从分子晶体到导电塑料。我强调了拟议工作计划的变革性影响的潜力，我们将使用新的制造协议来制造设备，然后用复杂的方法研究它们。我的工作的影响将是开发一个严格的框架来理解和控制光如何与这些相互作用。从长远来看，这项资助将促进人们对塑料半导体光物理学的全面理解，将经典聚合物科学、凝聚态物理学和化学物理学的概念联系起来。