Thermodynamic properties of BiH5 and BiH6 superconductors beyond the mean-field approximation

M.W. Jarosik¹, E.A. Drzazga-Szczęśniak ¹, I.A. Domagalska ², K.M. Szczęsniak ³, U. Stępień ¹

¹ Institute of Physics, Częstochowa University of Technology
² Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Góra
³ Faculty of Chemistry, University of Warsaw

The ab initio calculations suggest [1], that the high-pressure (p=200 GPa) superconducting state in BiH₅ and BiH₆ compounds characterizes with a high value of the critical temperature (T_C~100K). Due to the large value of the electron-phonon coupling constant (λ~1.2), the thermodynamic parameters of the superconducting phase in BiH₅ and BiH₆ have been determined beyond the mean-field approximation - in the framework of the Eliashberg equations formalism. We have calculated the dependence of the order parameter (Δ) and the wave function renormalization factor on the temperature. Then we have estimated the free energy difference between the superconducting state and the normal state, the thermodynamic critical field (H_C) and the specific heat of the superconducting state (CS) and the normal state (C_N). The values of the dimensionless ratios R_Δ=2Δ(0)/k_B T_C, R_C=ΔC(T_C )/C^N (T_C ) and R_H T_C C^N (T_C )/H_C² (0) are equal R_{ΔBiH_5}=4.17 and R_{ΔBiH_6}=4.20, R_{CBiH_5}=2.54 and R_{CBiH_6}=2.58, R_{HBiH_5}=0.146 and R_{HBiH_6}=0.146 respectively.

[1] Y.Ma, D. Duan, D. Li, Y. Liu, F. Tian, H. Yu, C. Xu, Z. Shao, B. Liu and T. Cui, High-pressure structures and superconductivity of bismuth hydrides, arXiv:1511.05291

Photoelectron spectra and entanglement in an auto-ionization system interacting with a neighbor atom

J. Perina Jr.¹, A. Luks ¹, V. Perinova¹, W. Leonski²

¹ Palacky University, Joint Laboratory of Optics, 17. listopadu 12, 772 07 Olomouc, Czech Republic
² Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Gora, Prof. Z. Szafrana 4a, 65-516 Zielona Gora, Poland

Long-time photoelectron ionization spectra of a system interacting with a neighbor two-level atom are investigated using the Laplace-transform method. Also auto-ionization levels are considered. These spectra are typically composed of several peaks. Conditions for the occurrence of Fano and Fano-like zeros are revealed. Photoelectron ionization spectra conditioned by the measurement on the two-level atom show oscillations at the Rabi frequency of the neighbor two-level atom. The presence of spectral dynamical zeros occurring in the conditioned spectra periodically with the Rabi period is predicted. Also entanglement between an ionized electron and that bound on the two-level system is analyzed using negativity. Conditions for the generation of highly entangled states of two electrons are found. Two-dimensional spectral density of negativity is defined. It allows to identify spectrally local entanglement between two electrons resembling that found in the system of two interacting qubits. It reveals that entanglement is 'concentrated' around spectral peaks.