Spatial control of heavy-fermion superconductivity in CeIrIn ₅

Abstract

The ability to spatially modulate the electronic properties of solids has led to landmark discoveries in condensed matter physics as well as new electronic applications. Although crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches to spatially modulating their properties exist. Here we demonstrate spatial control over the superconducting state in mesoscale samples of the canonical heavy-fermion superconductor CeIrIn5. We use a focused ion beam (FIB) to pattern crystals on the microscale, which tailors the strain induced by differential thermal contraction into specific areas of the device. The resulting non-uniform strain fields induce complex patterns of superconductivity due to the strong dependence of the transition temperature on the strength and direction of strain. Electrical transport and magnetic imaging of devices with different geometry show that the obtained spatial modulation of superconductivity agrees with predictions based on finite element simulations. These results present a generic approach to manipulating electronic order on micrometer length scales in strongly correlated matter.Heavy fermion materials exhibit a rich competition between metallic, superconducting, and magnetically ordered ground states. The ability to locally control electronic properties within these materials would enable the design of new correlated states both for fundamental research and for applications. Alternative approaches to achieve spatially modulated correlations involve modulating the

Controlling superconductivity of CeIrIn$_5$ microstructures by substrate selection

“…Around 500 mK, a first transition takes place arising from the bulk slabs outside the bridge. Below this temperature, the resistivity gradually decreases only to end up around 0.25 µΩcm, a value in good agreement with previous reports in the normal state 9 . The gradual decrease of resistivity is likely due to a combination of the usual metallic conductivity of CeIrIn 5 above T c and the region of partially suppressed superconductivity extending a few µm from either end of the bridge.…”

“…Strategies do exist to induce controlled local strains in certain two-dimensional materials 7,8 , but these do not translate well to three-dimensional solids, while a method to control strain locally could enable both novel types of basic science experiments as well as applications. Recently, controlled T c landscapes imprinted by static strain gradient fields of CeIrIn 5 have been demonstrated 9 . The approach exploits the high sensitivity of the superconducting critical temperature, T c , on directional strain, which translates strain gradients into T c gradients.…”

“…Previous work on CeIrIn 5 9 and other materials 15 focused exclusively on sapphire as a substrate, while here we employ various materials to engineer the strain. Sapphire has a small coefficient of thermal expansion (α = 1 L dL dT ) and hence contracts little when cooled down.…”

Scanning SQUID microscopy in a cryogen-free dilution refrigerator

“…2 shows an example of measurements on a CeIrIn 5 microstructure studied in Ref. 24 taken with the scanning SQUID microscope described here. We used a SQUID with a ∼1.5 µm sensitive area (pickup loop) and a ∼6 µm on-chip field coil which enables local magnetic susceptibility measurements.…”

“…The gold is removed in the active area of the device, and four electrical contacts are separated by cutting trenches (black in the image) using a FIB again (see Ref. 24 for details). The images were taken at 225 mK at which all parts of the CeIrIn 5 structure were superconducting.…”