Novel categories of electronic devices and quantum materials are obtained by pipelining the unitary evolution of electron quantum states as described by Schroedingers equation with non-unitary processes that interrupt the coherent propagation of elec
trons. These devices and materials reside in the fascinating transition regime between quantum mechanics and classical physics. The devices are designed such that a nonreciprocal unitary state evolution is achieved by means of a broken inversion symmetry, for example as induced at material interfaces. This coherent state evolution is interrupted by individual inelastic scattering events caused by defects coupled to an environment. Two-terminal non-unitary quantum devices, for example, feature nonreciprocal conductance in linear response. Thus, they are exemptions to Onsagers reciprocal relation, and they challenge the second law of thermodynamics. Implementing the device function into the unit cells of materials or meta-materials yields novel functionalities in 2D and 3D materials, at interfaces, and in heterostructures.
The decoherence of quantum states defines the transition between the quantum world and classical physics. Decoherence or, correspondingly, quantum mechanical collapse events pose fundamental questions regarding the interpretation of quantum physics.
They are also technologically relevant because they limit the coherent information processing performed by quantum computers. We have discovered that this transition regime enables a novel type of matter transport. Applying this discovery, we present nanoscale devices in which random quantum collapse events produce fundamentally novel phenomena by interrupting the unitary dynamics of electron wave packets. For most of the time, however, the wave packets proceed in coherent superpositions. Geometrically asymmetric conductors with mesoscopic length scales act as rectifiers with unique properties. They function in linear response, so Onsagers reciprocity relations do not apply to transport of this kind. The interface between the quantum and the classical worlds therefore provides a novel transport regime of value for the realization of a new category of mesoscopic electronic devices. These devices provide functions that have been considered impossible until now.
Atomically thin ferromagnetic and conducting electron systems are highly desired for spintronics, because they can be controlled with both magnetic and electric fields. We present (SrRuO3)1-(SrTiO3)5 superlattices and single-unit-cell-thick SrRuO3 sa
mples that are capped with SrTiO3. We achieve samples of exceptional quality. In these samples, the electron systems comprise only a single RuO2 plane. We observe conductivity down to 50 mK, a ferromagnetic state with a Curie temperature of 25 K, and signals of magnetism persisting up to approximately 100 K.
The possible existence of short-channel effects in oxide field-effect transistors is investigated by exploring field-effect transistors with various gate lengths fabricated from LaAlO$_3$-SrTiO$_3$ heterostructures. The studies reveal the existence o
f channel-length modulation and drain-induced barrier lowering for gate lengths below 1 {mu}m, with a characteristic behavior comparable to semiconducting devices. With the fabrication of field-effect transistors with gate lengths as small as 60 nm the results demonstrate the possibility to fabricate by electron-beam lithography functional devices based on complex oxides with characteristic lengths of several ten nanometers.
We present a study of the lattice response to the compressive and tensile biaxial stress in La0.67Sr0.33MnO3 (LSMO) and SrRuO3 (SRO) thin films grown on a variety of single crystal substrates: SrTiO3, DyScO3, NdGaO3 and (La,Sr)(Al,Ta)O3. The results
show, that in thin films under misfit strain, both SRO and LSMO lattices, which in bulk form have orthorhombic (SRO) and rhombohedral (LSMO) structures, assume unit cells that are monoclinic under compressive stress and tetragonal under tensile stress. The applied stress effectively modifies the BO6 octahedra rotations, which degree and direction can be controlled by magnitude and sign of the misfit strain. Such lattice distortions change the B-O-B bond angles and therefore are expected to affect magnetic and electronic properties of the ABO3 perovskites.
