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Magnetic field-induced changes in the electrical resistance of materials reveal insights into the fundamental properties governing their electronic and magnetic behavior. Various classes of magnetoresistance have been realized, including giant, colossal, and extraordinary magnetoresistance, each with distinct physical origins. In recent years, extreme magnetoresistance (XMR) has been observed in topological and non-topological materials displaying a non-saturating magnetoresistance reaching 103−108% in magnetic fields up to 60 T. XMR is often intimately linked to a gapless band structure with steep bands and charge compensation. Here, we show that a linear XMR of 80,000% at 15 T and 2 K emerges at the high-mobility interface between the large band-gap oxides γ-Al2O3 and SrTiO3. Despite the chemically and electronically very dissimilar environment, the temperature/field phase diagrams of γ-Al2O3/SrTiO3 bear a striking resemblance to XMR semimetals. By comparing magnetotransport, microscopic current imaging, and momentum-resolved band structures, we conclude that the XMR in γ-Al2O3/SrTiO3 is not strongly linked to the band structure, but arises from weak disorder enforcing a squeezed guiding center motion of electrons. We also present a dynamic XMR self-enhancement through an autonomous redistribution of quasi-mobile oxygen vacancies. Our findings shed new light on XMR and introduce tunability using dynamic defect engineering. Extreme magnetoresistance is characterized by a large and non-saturating magnetoresistance. Typically, it is observed in materials with compensated bandstructures, however, here, Christensen et al demonstrate a large and non-saturating magnetoresistance in a γAl2O3/SrTiO3 heterostructure, which is related to disorder, rather than the materials bandstructure. [ABSTRACT FROM AUTHOR]

The development of "fault-tolerant" quantum computers, unaffected by noise and decoherence, is one of the fundamental challenges in quantum technology. One of the approaches currently followed is the realization of "topologically protected" qubits which make use of quantum systems characterized by a degenerate ground state of composite particles, known as "non-Abelian anyons", able to encode and manipulate quantum information in a non-local manner. In this paper, we discuss the potential of quasi-two-dimensional electron gas (q2DEG) at the interface between band insulating oxides, like LaAlO3 and SrTiO3, as an innovative technological platform for the realization of topological quantum systems. Being characterized by a unique combination of unconventional spin-orbit coupling, magnetism, and 2D-superconductivity, these systems naturally possess most of the fundamental characteristics needed for the realization of a topological superconductor. These properties can be widely tuned by electric field effect acting on the orbital splitting and occupation of the non-degenerate 3dxy and 3dxz, yz bands. The topological state in oxide q2DEGs quasi-one-dimensional nanochannels could be therefore suitably controlled, leading to conceptual new methods for the realization of a topological quantum electronics based on the tuning of the orbital degrees of freedom. [ABSTRACT FROM AUTHOR]

The magnetic moment and relaxation rates in Bi2Sr2CaCu2O8+δ crystals exhibit remarkable dependence on the sample size in the vicinity of the vortex order-disorder phase transition line. Specifically, we find that: s1d the magnitude of the normalized magnetic moment increases as the sample size decreases, (2) the relaxation rate increases with the sample size, and (3) the difference between the relaxation rates in samples of different size, decreases with temperature and field. These phenomena are attributed to dynamic coexistence of quasi-ordered and metastable disordered vortex states in the samples, in the temperature and field range near the vortex phase transition. [ABSTRACT FROM AUTHOR]

The pinning mechanism in La1.85Sr0.15CuO4 (LaSCO) was investigated by analyzing the critical current dependence on field and temperature. Unlike other high temperature superconductors such as YBa2Cu3O7, DyBa2Cu3O7-δ, and Nd1.85Ce0.15CuO4-δ, which exhibit a single pinning mechanism over wide temperature and magnetic field ranges, our data in LaSCO show a clear crossover from δl to δTc pinning with temperature or field. While δl pinning is effective at low fields or low temperatures, δTc pinning dominates at high fields or high temperatures. Implications of the pinning mechanism crossover on the unique behavior of the second magnetization peak in LaSCO are discussed. [ABSTRACT FROM AUTHOR]

Local magnetization curves at different times, extracted from high-temporal resolution magneto-optical measurements in Bi[SWUB2]Sr[SUB2]CaCu[SUB2]O[SUB8+δ], demonstrate the absence of the second magnetization peak at short times, its appearance at longer times, and the movement of its onset toward higher-induction fields approaching the thermodynamic vortex order-disorder transition field. We relate this phenomena to metastable disordered states induced by edge contamination for inductions in the vicinity of the order-disorder vortex phase transition. We show that the time evolution of the second magnetization peak is governed by the relaxation times of the metastable disordered vortex states. [ABSTRACT FROM AUTHOR]

A high temporal resolution magneto-optical system is employed to follow the crystallization process of the quasiordered vortex state in Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+δ] crystals following a sudden change in the applied magnetic field. Two types of experiments are performed. In the first one the sample is suddenly exposed to a steady magnetic field smaller than the vortex order-disorder transition field, B[sub od]. In the second type of experiment the sample is initially exposed to an external field larger than B[sub od], and then the field is suddenly reduced. The two types of experiments reveal growth of the quasiordered state proceeding in opposite directions: from the sample center toward its edge in the first experiment, and from the sample edge toward the center in the second experiment. This motion enables tracing of the time evolution of the thermodynamic quasiordered vortex phase in the early stages of its formation. © 2001 American Institute o! f Physics. A high temporal resolution magneto-optical system is employed to follow the crystallization process of the quasiordered vortex state in Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+δ] crystals following a sudden change in the applied magnetic field. Two types of experiments are performed. In the first one the sample is suddenly exposed to a steady magnetic field smaller than the vortex order-disorder transition field, B[sub od]. In the second type of experiment the sample is initially exposed to an external field larger than B[sub od], and then the field is suddenly reduced. The two types of experiments reveal growth of the quasiordered state proceeding in opposite directions: from the sample center toward its edge in the first experiment, and from the sample edge toward the center in the second experiment. This motion enables tracing of the time evolution of the thermodynamic quasiordered vortex phase in the early stages of its formation. © 2001 American Insti! tute of Physics. [ABSTRACT FROM AUTHOR]

Scanning superconducting quantum interference device (SQUID) measurements recently revealed enhanced channels of conductivity at the conducting LaAlO/SrTiO (LAO/STO) interface (Kalisky et al. Nat. Mater. 12, 1091 2013). The orientation of the channels and their thermal behavior suggest that they originate as a consequence of the STO tetragonal domain formation which sets in below ∼105 K. In this work, we use polarized light microscopy to acquire images of the tetragonal domains in the same group of LAO/STO samples. We looked at the configuration of the domains (orientation and spacing) and followed their behavior as a function of temperature and back-gate voltage. The optical data agrees with the electrical behavior mapped magnetically. This direct and independent study of the domain structure confirms that the channel-like conductivity in LAO/STO is due to the STO tetragonal domain structure and emphasizes the importance of STO physics to the interfacial properties. These results demonstrate how small structural changes in perovskite crystals strongly influence the electronic characteristics of heterostructures. [ABSTRACT FROM AUTHOR]

A study of the DC I-V curves of BSCCO tapes exposed to AC perpendicular and parallel magnetic fields is presented. AC magnetic fields with amplitudes up to 700 G and frequencies from 1 to 430 Hz have been applied perpendicular and parallel to tapes carrying DC currents at T = 77 K. Both field orientations result in a significant DC electric field increase, in comparison to applying DC magnetic fields of the same intensity. However, the observed I-V curves behavior is different for the perpendicular and parallel cases. In the perpendicular case, we distinguish between two frequency regimes: for frequencies above 40 Hz, the observed I-V curves obey the empirical power law dependence with current density, J c, and power index, n, that strongly depend on the field amplitude. For frequencies below 20 Hz, the observed I-V curves deviate from power law description. In the parallel field case, the I-V curve can be regarded as a superposition of an additional DC voltage over the no field I-V curve. This additional voltage increases with increasing current, peaks near the critical current and decreases thereafter. The results are discussed assuming a narrowing down of the DC current path under the application of a perpendicular AC field. Shaking of the pinned vortices under the application of a parallel AC field is assumed for explaining the results in this case. [ABSTRACT FROM AUTHOR]

We employed a scanning Hall probe microscope to detect the hopping of individual vortices between pinning sites along grain boundaries in YBa2Cu3O6+δ thin films in the presence of an applied current. Detecting the motion of individual vortices allowed us to probe the current-voltage (I-V) characteristics of the grain boundary with voltage sensitivity below a femtovolt. We find a very sharp onset of dissipation with V∝In with an unprecedented high exponent of n≈290 that shows essentially no dependence on temperature or grain boundary angle. Our data have no straightforward explanation within the existing grain boundary transport models. [ABSTRACT FROM AUTHOR]