We calculate the core-hole spectral density in a pristine graphene, where the density of states of itinerant electrons goes linearly to zero at the Fermi level. We consider explicitly two models of electron-hole inter...We calculate the core-hole spectral density in a pristine graphene, where the density of states of itinerant electrons goes linearly to zero at the Fermi level. We consider explicitly two models of electron-hole interaction. In the unscreened Coulomb interaction model, the spectral density is similar to that in metal (for local interaction). Thus there is no δ-function singularity in the core-hole spectral density. In the local interaction model, the δ-function singularity survives, but the interaction leads to the appearance of the background in the spectral density.展开更多
Quantum processes of inherent dynamical nature,such as quantum walks,defy a description in terms of an equilibrium statistical physics ensemble.Until now,identifying the general principles behind the underlying unitar...Quantum processes of inherent dynamical nature,such as quantum walks,defy a description in terms of an equilibrium statistical physics ensemble.Until now,identifying the general principles behind the underlying unitary quantum dynamics has remained a key challenge.Here,we show and experimentally observe that split-step quantum walks admit a characterization in terms of a dynamical topological order parameter(DTOP).This integer-quantized DTOP measures,at a given time,the winding of the geometric phase accumulated by the wavefunction during a quantum walk.We observe distinct dynamical regimes in our experimentally realized quantum walks,and each regime can be attributed to a qualitatively different temporal behavior of the DTOP.Upon identifying an equivalent manybody problem,we reveal an intriguing connection between the nonanalytic changes of the DTOP in quantum walks and the occurrence of dynamical quantum phase transitions.展开更多
文摘We calculate the core-hole spectral density in a pristine graphene, where the density of states of itinerant electrons goes linearly to zero at the Fermi level. We consider explicitly two models of electron-hole interaction. In the unscreened Coulomb interaction model, the spectral density is similar to that in metal (for local interaction). Thus there is no δ-function singularity in the core-hole spectral density. In the local interaction model, the δ-function singularity survives, but the interaction leads to the appearance of the background in the spectral density.
基金supported by the National Key Research and Development Program of China(Nos.2017YFA0304100 and 2016YFA0302700)National Natural Science Foundation of China(Nos.61327901,11874343,11474267,11774335 and 61322506)+6 种基金Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-SLH003)Fundamental Research Funds for the Central Universities(No.WK2470000026)National Postdoctoral Program for Innovative Talents(No.BX201600146)China Postdoctoral Science Foundation(No.2017M612073)Anhui Initiative in Quantum Information Technologies(Grant Nos.AHY020100 and AHY060300)financial support from the German Research Foundation(DFG)through the Collaborative Research Centre SFB 1143financial support from the Deutsche Forschungsgemeinschaft via the Gottfried Wilhelm Leibniz Prize program.
文摘Quantum processes of inherent dynamical nature,such as quantum walks,defy a description in terms of an equilibrium statistical physics ensemble.Until now,identifying the general principles behind the underlying unitary quantum dynamics has remained a key challenge.Here,we show and experimentally observe that split-step quantum walks admit a characterization in terms of a dynamical topological order parameter(DTOP).This integer-quantized DTOP measures,at a given time,the winding of the geometric phase accumulated by the wavefunction during a quantum walk.We observe distinct dynamical regimes in our experimentally realized quantum walks,and each regime can be attributed to a qualitatively different temporal behavior of the DTOP.Upon identifying an equivalent manybody problem,we reveal an intriguing connection between the nonanalytic changes of the DTOP in quantum walks and the occurrence of dynamical quantum phase transitions.
