Phase Transitions in 2D Superconductors Modelled with Microscopic Framework and Coulomb-Induced Regularization

Superconductivity in two-dimensional materials often exists in a state where subtle fluctuations of the material’s phase significantly impact its properties, challenging conventional theories. F. Yang and L. Q. Chen, along with their colleagues, now present a comprehensive theoretical framework that accurately describes these phase transitions in disordered 2D superconductors, moving beyond simpler approximations. Their method incorporates the behaviour of electrons, energy fluctuations, and the influence of long-range interactions, offering a unified description of how superconductivity emerges and responds to imperfections. Remarkably, this approach successfully reproduces experimental observations from bilayer molybdenum disulfide and disordered indium oxide thin films, providing a powerful new tool for understanding and predicting the behaviour of these advanced superconducting materials and opening avenues for future materials design.

Superconductivity, 2D Materials and Disordered Systems

This collection of research explores the fascinating world of superconductivity, particularly within two-dimensional materials and disordered systems. It encompasses studies of conventional and unconventional superconductors, the unique properties of materials like molybdenum disulfide and strontium titanate, and the powerful computational methods used to understand these complex phenomena. The research highlights connections between superconductivity, materials disorder, and the fundamental fluctuations that govern these quantum states, suggesting exciting avenues for future discovery. A central theme is the investigation of superconductivity in thin films and disordered materials, focusing on how imperfections and disorder affect the superconducting state.

Scientists are exploring the transition between superconductivity and insulation, the role of preformed Cooper pairs, and the existence and properties of Higgs modes in both pristine and disordered materials. The emergence of superconductivity in two-dimensional materials, where valley degrees of freedom and external gating can be used to tune the superconducting properties, is also a key focus. Beyond superconductivity, the research delves into the electronic and optical properties of two-dimensional materials, including transition metal dichalcogenides, working to understand their band structure, spin polarization, and spin relaxation mechanisms. Studies of ferroelectric materials, such as strontium titanate, reveal the behavior of quantum paraelectricity, where quantum fluctuations suppress the formation of ferroelectric order, and the potential for controlling ferroelectric polarization using terahertz radiation.

Computational methods, including density functional theory, play a crucial role in modeling these materials and guiding the design of new quantum materials. This body of work reveals strong connections that point towards promising research directions. A key area is understanding how disorder affects superconductivity in two-dimensional materials, including investigating the transition between superconducting and insulating states and intentionally engineering disorder to enhance or suppress superconductivity. Combining two-dimensional materials with ferroelectrics offers the potential for novel functionalities, such as using ferroelectric polarization to control the properties of nearby superconductors. Terahertz spectroscopy and control of quantum materials provide a powerful tool for probing and manipulating these systems, including directly observing Higgs modes and dynamically controlling the superconducting state. Finally, computational materials design is crucial for predicting the properties of new materials and designing novel heterostructures with tailored properties.

Unified Theory of 2D Superconducting Fluctuations

Scientists have developed a comprehensive theoretical framework to understand superconductivity in two-dimensional materials. This new approach goes beyond traditional theories by simultaneously considering multiple fluctuating phenomena, including the behavior of quasiparticles, phase fluctuations, and topological vortex-antivortex fluctuations, all influenced by long-range Coulomb interactions. This unified description accurately captures the complex interplay of these factors, allowing for a self-consistent treatment of the superconducting gap and superfluid density. The research demonstrates that the superconducting gap in two-dimensional systems remains robust against certain fluctuations due to Coulomb interactions.

Simultaneously, the proliferation of other fluctuations drives a separation between the global superconducting transition temperature and the temperature at which the energy gap closes. By applying this framework to bilayer molybdenum disulfide and disordered indium oxide films, scientists have quantitatively reproduced key experimental observations, confirming the model’s accuracy and predictive power. This work establishes a valuable theoretical tool for understanding phase-fluctuation-dominated superconductivity and paves the way for future advancements in the field.

Disorder, Fluctuations, and Robust 2D Superconductivity

This research presents a comprehensive theoretical framework for understanding superconductivity in disordered two-dimensional materials. Scientists developed a model that simultaneously accounts for the behavior of quasiparticles, phase fluctuations, and the influence of long-range Coulomb interactions. This unified approach successfully explains previously observed phenomena and accurately captures the complex interplay of these factors, allowing for a self-consistent determination of the superconducting gap and superfluid density. The research demonstrates that the superconducting gap remains robust against certain fluctuations due to Coulomb interactions, while the proliferation of other fluctuations drives a separation between the global superconducting transition temperature and the temperature at which the energy gap closes. Applications of this framework to bilayer molybdenum disulfide and disordered indium oxide films quantitatively reproduce key experimental observations, confirming the model’s accuracy and predictive power. This work establishes a valuable theoretical tool for understanding phase-fluctuation-dominated superconductivity and provides insights into the fundamental mechanisms governing these materials.

Disorder, Coulomb Interactions, and 2D Superconductivity

This research presents a comprehensive theoretical framework for understanding superconductivity in disordered two-dimensional materials. Scientists developed a self-consistent model that simultaneously accounts for the behavior of quasiparticles, phase fluctuations, and the influence of long-range Coulomb interactions. This unified approach successfully explains previously observed phenomena and accurately captures the complex interplay of these factors. The research demonstrates that the superconducting gap remains robust against certain fluctuations due to Coulomb interactions, while the proliferation of other fluctuations drives a separation between the global superconducting transition temperature and the temperature at which the energy gap closes. The framework accurately reproduces experimental observations from materials like bilayer molybdenum disulfide and disordered indium oxide films, quantitatively matching key characteristics of their superconducting behavior. This work provides a robust foundation for further investigations into phase-fluctuation-dominated superconductivity and offers valuable insights into the behavior of complex materials.