Plausible room temperature superconductivity and physical properties of cuprate superconductors based on a rigorous slave-boson representation of the t–J Hamiltonian

Abstract

We present newly clarified physical properties of cuprate superconductors based on careful examinations of our earlier studies and show plausibility of room temperature superconductivity. As well known, one of the major challenging problems in high-temperature superconductivity is to reproduce the observed phase diagrams (Chatterjee, PNAS 108:9346–9349, 2011; Oda, J Phys Soc Jpn 69:983–984, 2000; Nakano, J Phys Soc Jpn 67:2622–2625, 1998; Schmidt, New J Phys 13:065014, 2011, Cyr-Choiniere (Pseudogap temperature ${T}^{*}$ of cuprate from the Nernst effect, cond-mat.supr-con, 2017; Yoshida et al. Nature 454:1072, 2008) displaying both the monotonously decreasing pseudogap temperature $T^{*}$ and the dome-shaped superconducting transition temperature $T_\mathrm{c}$ in the plane of temperature vs. hole concentration. Earlier we Lee et al. (Phys Rev B 64:052501–052504, 2001), Lee and Salk (Phys Rev B 71:134518, 2005), (66:054427, 2002), (J Korean Phys Soc 37:545–551, 2000) reported successful reproductions of the phase diagrams using our slave-boson theory of U(1) and SU(2) symmetry for the t–J Hamiltonian. Later we further showed that predictions (Shin and Salk, Int J Mod Phys B 29:1542003–1542011, 2015; Shin et al. J Supercond Nov Magn 23:637–640, 2010; Eom et al. Int J Mod Phys B 21:3132, 2007) of both the temperature and doping dependence of magnetic susceptibility and the universal linear scaling behavior between the magnetic resonance energy, $E_{{\mathrm{res}}}$ and $T_\mathrm{c}$, are consistent with inelastic neutron scattering (INS) measurements (Dai et al. Science 284:1344, 1999; He et al. Phys Rev Lett 86:1610, 2001; Bourges et al. Phys C 424:45, 2005; Stock et al. Phys Rev B 75:172510, 2007; Wakimoto et al. Phys Rev Lett 98:247003, 2007; Yu et al. Nat Phys 5:873, 2009; Isonov et al. Phys Rev B 83:214520, 2011; Keimer et al. Nature 518:179, 2015). In this work we present further clarifications of physics involved with both the phase diagrams and the INS measurements. For this cause we explore the role of spin–charge coupling on both the universal behavior of ${T^{*}}/T_\mathrm{c}$ from the phase diagrams (Chatterjee, 2011) and the universal scaling ratio of ${E_{{\mathrm{res}}}}/{k_\mathrm{B} T_\mathrm{c}}$ from the INS measurements (He et al. Phys Rev Lett 86:1610, 2001; Bourges et al. Phys C 424:45, 2005; Yu et al. Nat Phys 5:873, 2009). Both of them are found to be independent of the Heisenberg exchange coupling constant J, involving the distinctive presence of spin pairing order in association with the two energy scales, the magnetic resonance energy and the pseudogap temperature. In addition, we also discuss the J independent universal behavior of the superfluid density vs. the superconducting transition temperature. We explain most specifically physics on how all of these universal behaviors are related to the presence of spin–charge coupling. The spin–charge coupling here refers to coupling between the spin (spinon) paring order and the charge (holon) paring order which is manifested in our rigorous derivation (Lee et al. 2001; Lee and Salk, 2005, 2002) of the slave-boson-based t–J Hamiltonian. In short, we plan to explain salient physics involved with the observed universal behaviors above. Noting that in association with the universal scaling behaviors of both ${T^{*}}/T_\mathrm{c}$ and ${E_{\mathrm{res}}}/{k_\mathrm{B} T_\mathrm{c}}$ the higher the J, the higher the $T_\mathrm{c}$, we propose that room temperature superconductivity is plausible with proper chemical synthesis of cuprate oxides meeting a suitably high J value.