Coupled Cu and Mn charge and orbital orders in YBa2Cu3O7/Nd0.65(Ca1-ySry)0.35MnO3 multilayers

Abstract

The observation of a charge density wave in the underdoped cuprate high T c superconductors (Cu-CDW) raised a debate about its relationship with superconductivity. In bulk YBa 2 Cu 3 O 7−δ the Cu-CDW is incipient and mainly pinned by defects. Nevertheless, a large magnetic field can induce a true long-range Cu-CDW order as it suppresses superconductivity. An enhanced Cu-CDW order was also observed in YBa 2 Cu 3 O 7 /La 2/3 Ca 1/3 MnO 3 multilayers. Here, we show that the magnitude of the Cu-CDW in YBa 2 Cu 3 O 7−δ / Nd 0.65 (Ca 1y Sr y) 0.35 MnO 3 multilayers can be varied by adjusting the strength of the manganite charge and orbital order via the Sr content (tolerance factor). Furthermore, we resolve the reconstruction of the crystal field levels of the interfacial Cu ions that are also affected by the manganite charge and orbital order. This tuneable interfacial coupling and Cu-CDW in YBa 2 Cu 3 O 7−δ can be used for studying the relationship between the Cu-CDW and superconductivity and, possibly, for inducing new intertwined quantum states.

Granular superconductivity and charge/orbital order in YBa2Cu3O7 /manganite trilayers

“…Moreover, it remains to be clarified whether the disorder and the domain boundaries of the Mn-CO/OO are directly "imprinted" as superconducting grain boundaries into the YBCO layer. Alternatively, they may stabilize a chargeor spin-ordered state in the YBCO layer [32,47] that forms its own domain state and competes with superconductivity or possibly even gives rise to an intertwined state with domain boundaries at which the superconducting coherence is broken [58].…”

“…This is likely due to a broadening of the transition and an enhanced localization of the charge carrier at T > T CO/OO due to the disorder and residual strain effects that are inherent to thin films and most likely prevent the observation of a clear effect on a macroscopic scale experiment such as resistivity measurements. In fact, the development of the Mn-CO/OO below T CO/OO ≈ 240 K has been observed by micro-Raman spectroscopy in the NCSMO layer with y = 0.2 in terms of an anomalous temperature dependence of certain modes that are very sensitive to local Jahn-Teller distortions [47] (see also Sec. III E).…”

Backfolded acoustic phonons as ultrasonic probes in metal-oxide superlattices

“…grown by PLD on La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 (LSAT) substrates that are (0 0 1) oriented following the process described in Refs. [15] and [31]. The superlattices involve 10 repetitions of cuprate-manganite layers, whose thickness we denote using the following scheme; PLCMO(10 nm)/YBCO(7 nm) translates to a 7-nm-thick YBCO layer grown on top of a 10-nm-thick PLCMO layer.…”

“…This is due to the various types of magnetic, charge, ferroelectric, and superconducting orders that the constituent metal-oxide layers can host [13,14]. The novel properties of thin-film multilayers and superlattices result from interactions across the interface, such as spin and orbital reconstruction, charge transfer, and phonon coupling [3][4][5]7], as well as some hitherto unidentified mechanisms [9,15]. The additional periodicity introduced in superlattice structures with smooth interfaces can also be used to tune the thermal conductivity via the opening of phononic band gaps [16].…”

“…Growth techniques for such samples include [18] pulsed laser deposition (PLD) [19], molecular beam epitaxy [20], and sputtering [21]. * benjamin.mallett@gmail.com Here we report on the observation of low-frequency Raman modes in metal-oxide superlattices, with a focus on superlattices of the high-temperature superconductor YBa 2 Cu 3 O 7 (YBCO) and RMnO 3 manganites, which are exemplary multilayers for displaying the effects described above [7,9,15]. The low-energy modes are optical phonons which arise in superlattices due to the backfolding of the c-axis acoustic phonon branch and, to the best of our knowledge, are detected for the first time in metal-oxide heterostructures.…”