The excitonic insulator(EI)is a more than 60-year-old theoretical proposal that is still elusive.It is a purely quantum phenomenon involving the spontaneous generation of excitons in quantum mechanics and the spontane...The excitonic insulator(EI)is a more than 60-year-old theoretical proposal that is still elusive.It is a purely quantum phenomenon involving the spontaneous generation of excitons in quantum mechanics and the spontaneous condensation of excitons in quantum statistics.At this point,the excitons represent the ground state rather than the conventional excited state.Thus,the scarcity of candidate materials is a key factor contributing to the lack of recognized EI to date.In this review,we begin with the birth of EI,presenting the current state of the field and the main challenges it faces.We then focus on recent advances in the discovery and design of EIs based on the first-principles Bethe-Salpeter scheme,in particular the dark-exciton rule guided screening of materials.It not only opens up new avenues for realizing excitonic instability in direct-gap and wide-gap semiconductors,but also leads to the discovery of novel quantum states of matter such as half-EIs and spin-triplet EIs.Finally,we will look ahead to possible research pathways leading to the first recognized EI,both theoretically and computationally.展开更多
During actual high-speed flights,the electromagnetic(EM)properties of aircraft radomes are influenced by dielectric temperature drift,leading to substantial drift in the boresight errors(BSEs)from their room temperatu...During actual high-speed flights,the electromagnetic(EM)properties of aircraft radomes are influenced by dielectric temperature drift,leading to substantial drift in the boresight errors(BSEs)from their room temperature values.However,applying thermal loads to the radome during ground-based EM simulation tests is challenging.This paper presents an EM equivalent physical model(EEPM)for high-speed aircraft radomes that account for the effects of dielectric temperature drift.This is achieved by attaching dielectric slices of specific thicknesses to the outer surface of a room-temperature radome(RTR)to simulate the increase in electrical thickness resulting from high temperatures.This approach enables accurate simulations of the BSEs of high-temperature radomes(HTRs)under high-speed flight conditions.An application example,supported by full-wave numerical calculations and physical testing,demonstrates that the EEPM exhibits substantial improvement in approximating the HTR compared to the RTR,facilitating precise simulations of the BSEs of HTRs during high-speed flights.Overall,the proposed EEPM is anticipated to considerably enhance the alignment between the ground-based simulations of high-speed aircraft guidance systems and their actual flight conditions.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFA1406400 and 2020YFA0308800)the National Natural Science Foundation of China(Grant No.12474064)。
文摘The excitonic insulator(EI)is a more than 60-year-old theoretical proposal that is still elusive.It is a purely quantum phenomenon involving the spontaneous generation of excitons in quantum mechanics and the spontaneous condensation of excitons in quantum statistics.At this point,the excitons represent the ground state rather than the conventional excited state.Thus,the scarcity of candidate materials is a key factor contributing to the lack of recognized EI to date.In this review,we begin with the birth of EI,presenting the current state of the field and the main challenges it faces.We then focus on recent advances in the discovery and design of EIs based on the first-principles Bethe-Salpeter scheme,in particular the dark-exciton rule guided screening of materials.It not only opens up new avenues for realizing excitonic instability in direct-gap and wide-gap semiconductors,but also leads to the discovery of novel quantum states of matter such as half-EIs and spin-triplet EIs.Finally,we will look ahead to possible research pathways leading to the first recognized EI,both theoretically and computationally.
文摘During actual high-speed flights,the electromagnetic(EM)properties of aircraft radomes are influenced by dielectric temperature drift,leading to substantial drift in the boresight errors(BSEs)from their room temperature values.However,applying thermal loads to the radome during ground-based EM simulation tests is challenging.This paper presents an EM equivalent physical model(EEPM)for high-speed aircraft radomes that account for the effects of dielectric temperature drift.This is achieved by attaching dielectric slices of specific thicknesses to the outer surface of a room-temperature radome(RTR)to simulate the increase in electrical thickness resulting from high temperatures.This approach enables accurate simulations of the BSEs of high-temperature radomes(HTRs)under high-speed flight conditions.An application example,supported by full-wave numerical calculations and physical testing,demonstrates that the EEPM exhibits substantial improvement in approximating the HTR compared to the RTR,facilitating precise simulations of the BSEs of HTRs during high-speed flights.Overall,the proposed EEPM is anticipated to considerably enhance the alignment between the ground-based simulations of high-speed aircraft guidance systems and their actual flight conditions.
