The photon absorption edge in superconductors and gapped 1D systems

Abstract

Opening of a gap in the low-energy excitations spectrum affects the power-law singularity in the photon absorption spectrum $A(\Omega )$. In the normal state, the singularity, $A(\Omega )\propto [D/(\Omega -{\Omega }_{\mathrm{th}}){]}^{\alpha }$, is characterized by an interaction-dependent exponent $\alpha$. On the contrary, in the supeconducting state the divergence, $A(\Omega )\propto (D/\Delta {)}^{\alpha }(\Omega -{\tilde{\Omega }}_{\mathrm{th}}{)}^{-1/2}$, is interaction-independent, while threshold is shifted, ${\tilde{\Omega }}_{\mathrm{th}}={\Omega }_{\mathrm{th}}+\Delta$; the ``normal-metal'' form of $A(\Omega )$ resumes at $(\Omega -{\tilde{\Omega }}_{\mathrm{th}})\gtrsim \Delta \exp (1/\alpha )$. If the core hole is magnetic, it creates in-gap states; these states transform drastically the absorption edge. In addition, processes of scattering off the magnetic core hole involving spin-flip give rise to inelastic absorption with one or several {\it real} excited pairs in the final state, yielding a structure of peaks in $A(\Omega )$ at multiples of $2\Delta$ above the threshold frequency. The above conclusions apply to a broad class of systems, e.g., Mott insulators, where a gap opens at the Fermi level due to the interactions.

6 pages, 5 figures; published version

References in corpus (8)

• Plasmon attenuation and optical conductivity of a two-dimensional electron gas
• Fermi Edge Singularities in Transport through Quantum Dots
• Noise at a Fermi-edge singularity
• Fermi-edge Singularity in II-VI Semiconductor Resonant Tunneling Structures
• Fermi-edge singularity in a spin-incoherent Luttinger liquid
• Fermi Edge Singularities in the Mesoscopic Regime: II. Photo-absorption Spectra
• Supergap anomalies in cotunneling between N-S and between S-S leads via a small quantum dot
• Two-Electron Linear Intersubband Light Absorption in a Biased Quantum Well

Cited by in corpus (3)

• The X-ray edge singularity in Quantum Dots
• Spin-Polarized Semiconductor Induced by Magnetic Impurities in Graphene
• Fermi-edge singularity in the vicinity of the resonant scattering condition