Higher superconducting transition temperature by breaking the universal pressure relation

Abstract

By investigating the bulk superconducting state via dc magnetization measurements, we have discovered a common resurgence of the superconductive transition temperatures (Tcs) of the monolayer Bi2Sr2CuO6+δ (Bi2201) and bilayer Bi2Sr2CaCu2O8+δ (Bi2212) to beyond the maximum Tcs (Tc-maxs) predicted by the universal relation between Tc and doping (p) or pressure (P) at higher pressures. The Tc of under-doped Bi2201 initially increases from 9.6 K at ambient to a peak at ~ 23 K at ~ 26 GPa and then drops as expected from the universal Tc-P relation. However, at pressures above ~ 40 GPa, Tc rises rapidly without any sign of saturation up to ~ 30 K at ~ 51 GPa. Similarly, the Tc for the slightly overdoped Bi2212 increases after passing a broad valley between 20-36 GPa and reaches ~ 90 K without any sign of saturation at ~ 56 GPa. We have therefore attributed this Tc-resurgence to a possible pressure-induced electronic transition in the cuprate compounds due to a charge transfer between the Cu 3 " # $% # and the O 2p bands projected from a hybrid bonding state, leading to an increase of the density of states at the Fermi level, in agreement with our density functional theory calculations. Similar Tc-P behavior has also been reported in the trilayer Br2Sr2Ca2Cu3O10+δ (Bi2223). These observations suggest that higher Tcs than those previously reported for the layered cuprate high temperature superconductors can be achieved by breaking away from the universal Tc-P relation through the application of higher pressures.Significance Statement: Achieving higher transition temperature (Tc) is a primary goal in superconductivity research. Tc and doping have been found to have a dome-like universal relation where the peak position is the maximum Tc-max, which is consistent with previous experimental results in the lower pressure range. By using our newly developed ultra-sensitive magnetization measurement technique under high pressure, we discovered a universal resurgence of Tc passing the peak predicted by the general Tc-p (doping) or -P (pressure) relation for cuprate high temperature superconductor and attribute the resurgence to a pressure-induced electronic transition, which is supported qualitatively by our density functional theory calculations. This offers a new way to raise the Tc of the layered cuprate high temperature superconductors to a new height.

Effects of a k⃗-dependent Hybridisation on the Fermi surface of an extended d–p Hubbard model

“…Such results are in agreement with recent experimental findings showing that the critical doping where the pseudogap closes is deeply affected by pressure [1]. In this sense, whereas the hybridization is susceptible to the pressure changes [22][23][24], the present results corroborate the experimental data [1] and indicates a new route for theoretical investigations of the Lifshitz transition and the pseudogap regime.…”

“…Nevertheless, the fact that the oxygen sites may be occupied by holes when the system is doped suggests that a model which also takes into account the oxygen can be more adequate to treat the doped regime of such systems [16][17][18][19][20][21]. In this sort of model, the hybridization between the d orbitals of the cooper and the p orbitals of the oxygen becomes an important parameter which is sensitive to changes of external pressure [22][23][24]. For the sake of simplicity, it is usual to consider the hybridization as a k-independent parameter [16,27,28].…”

Superconducting properties of (NH3)yLixFeSe0.5Te0.5 under pressure

“…The first discovery of a pressuredriven high-T c phase was reported for K 0.8 Fe 1.7 Se 2 , K 0.8 Fe 1.78 Se 2 and Tl 0.6 Rb 0.4 Fe 1.67 Se 2 crystals [6], and our group reported a very high value of T c (= 49 K) in (NH 3 ) y Cs x FeSe at 21 GPa [9], showing that the double-dome T c -p phase diagram consisted of two superconducting phases (SC-I and SC-II). As a matter of fact, such a double-dome T c -p phase diagram has also been reported for other materials such as Bi 2 Sr 2 CuO 6+δ [12] and FeS [13].…”

“…This is the most promising scenario for the origin of double-dome T c -p phase diagram. Actually, such a pressure-driven electronic transition is proposed for Bi 2 Sr 2 CuO 6+δ [12], as well as (NH 3 ) y Li x FeSe [10].…”

Room-temperature skyrmion phase in bulk Cu 2 OSeO 3 under high pressures

“…Our recently developed ultrasensitive high-pressure magnetization technique (19) was used to investigate the skyrmion phase evolution under high pressure. Under pressure the magnetic phase transition temperature T c , which defines the upper bound of the skyrmion phase, is shifted toward higher temperature as shown in Fig.…”