Optically driven giant superbunching from a single perovskite quantum dot

Photon superbunching is a signature of a strong correlation between photons, which is a crucial resource needed in quantum communication and computation. As such, a superbunched photon source based on a material with high quantum efficiency, like cesium lead halide perovskite, is highly desirable. Utilizing the large dark–bright exciton splitting in CsPbBr3 quantum dot (QD), the authors achieve a superbunching with a large g(2)(0) ≈ 30 from an optically driven single CsPbBr3 QD emission at cryogenic temperature. The cascaded emission is identified as the cause of this superbunching by utilizing second-order cross-correlation measurement and exploring the excitation power and temperature dependence of the bunching level. The findings have immediate implications on the basic understanding of a single perovskite QD emission and its application as a quantum light source.Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionThe authors acknowledge the financial support from the Singapore National Research Foundation through its Competitive Research Program (CRP Award No. NRF-CRP21-2018-0007, NRF-CRP22-2019-0004, and NRF-CRP23-2019-0002) and Quantum Engineering Program (QEP) and from Singapore Ministry of Education (MOE2016-T3-1-006 (S))

Quantum-metric-induced nonlinear transport in a topological antiferromagnet

The Berry curvature and quantum metric are the imaginary part and real part, respectively, of the quantum geometric tensor, which characterizes the topology of quantum states1. The Berry curvature is known to generate a number of important transport phenomena, such as the quantum Hall effect and the anomalous Hall effect2,3; however, the consequences of the quantum metric have rarely been probed by transport measurements. Here we report the observation of quantum-metric-induced nonlinear transport, including both a nonlinear anomalous Hall effect and a diode-like non-reciprocal longitudinal response, in thin films of a topological antiferromagnet, MnBi2Te4. Our observations reveal that the transverse and longitudinal nonlinear conductivities reverse signs when reversing the antiferromagnetic order, diminish above the Néel temperature and are insensitive to disorder scattering, thus verifying their origin in the band-structure topology. They also flip signs between electron- and hole-doped regions, in agreement with theoretical calculations. Our work provides a means to probe the quantum metric through nonlinear transport and to design magnetic nonlinear devices.National Research Foundation (NRF)W.G. acknowledges the financial support from the Singapore National Research Foundation through its Competitive Research Program (CRP Award No. NRF-CRP22-2019-0004). B.Y. acknowledges the financial support by the European Research Council (ERC Consolidator Grant No. 815869, ‘NonlinearTopo’) and Israel Science Foundation (ISF No. 2932/21). A.W. acknowledges the financial support from the National Natural Science Foundation of China (grant no. 12004056), Chongqing Research Program of Basic Research and Frontier Technology, China (grant no. cstc2021jcyj-msxmX0661) and Fundamental Research Funds for the Central Universities, China (grant no. 2022CDJXY-002). X.Z. acknowledges the financial support from the National Key Research and Development Program of the Ministry of Science and Technology of China (2019YFA0704901) and the National Natural Science Foundation of China (grant nos. 52125103 and 52071041)