Modification of structural disorder by hydrostatic pressure in the superconducting cuprate YBa2Cu3O6.73

Abstract

Compelling efforts to improve the critical temperature (T c ) of superconductors have been made through high-pressure application. Understanding the underlying mechanism behind such improvements is critically important, however, much remains unclear. Here we studied ortho-III YBa 2 Cu 3 O 6.73 (YBCO) using x-ray scattering under hydrostatic-pressure (HP) up to ~6.0 GPa. We found the reinforced oxygen order (OO) of YBCO under HP, revealing an oxygen rearrangement in the Cu-O layer, which evidently shows the charge transfer phenomenon between the CuO 2 plane and Cu-O layer. Concurrently, we also observed no disorder-pinned charge density wave (CDW) signature in CuO 2 plane under HP. This indicates that the oxygen rearrangement modifies the quenched disorder state in the CuO 2 plane.Using these results, we appropriately explain why pressure-condition can achieve higher T c compared with the optimal T c under ambient pressure in YBa 2 Cu 3 O 6+x . As an implication of these results, finally, we have discussed that the change in disorder could make it easier for YBa 2 Cu 3 O 6+x to undergo a transition to the nematic order under an external magnetic field.

Sensitivity of Tc to pressure and magnetic field in the cuprate superconductor YBa2Cu3Oy

“…Field and pressure are two complementary parameters with which to tune phase competition between CDW order and superconductivity in YBCO, in opposite directions. This is consistent with our interpretation that pressure suppresses CDW order in YBCO, as shown by x-ray studies in underdoped YBCO [24,25]. We mention that the same is seen in LBCO at p = 0.125, with pressure suppressing CDW order and raising T c [43].…”

“…Therefore, pressure is seen as a tuning parameter that weakens CDW order, with little direct effect on superconductivity or on the pseudogap phase. Recent x-ray studies observe that pressure suppresses CDW order in YBCO [24,25]. As a result, the increase of T c with pressure is a consequence of competition between superconductivity and charge order.…”

Peculiarities of pseudogap in Y0.95Pr0.05Ba2Cu3O7−δ single crystals under pressure up to 1.7 GPa

“…It is the weakly Pr doped samples that demonstrate interesting phenomena of suppression of the pseudogap state and anomalous extension of the temperature range of the linear ρ(T) dependence 18,24,36 . When pressure is applied, the volume of the unit cell decreases contributing to the ordering of the system leading to a decrease in the number of structural defects and a decrease in ρ 12,28,37 . At any rate, the mechanisms of influence of pressure on both T c and ρ are not fully understood, as the nature of the transport properties of HTSC is not completely clear.…”

“…The main contribution to the conductivity of cuprates is by the CuO 2 planes, between which there is a relatively weak interplanar interaction. It is assumed that the pressure leads to an increase in the density of charge carriers n f in the conducting CuO 2 planes and, as a result, to a decrease in ρ 12,28 . An increase in n f under pressure should also lead to an increase in T c , i.e.…”

Effect of Substituting a Fraction of Cu by La on the Transport Properties of YBa<sub>2</sub>(Cu<sub>1−x</sub>La<sub>x</sub>)<sub>3</sub>O<sub>7−δ</sub> Superconductor (0 ≤ x ≤ 0.06)

“…In almost all such cases, the destabilization of (YBCO) superconducting phases and consequently the degradation of superconductivity in these compounds have been determined at low substitution level. Also, the superconducting properties severely degraded by the substitution of transition elements in copper sites [9] [10], this suggesting that the principal component for superconductivity involves the (Cu-O) bonding.…”