We report on transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields. We observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowire for certain ranges of magnetic field and chemical potential. The ZBA can oscillate in width with either the magnetic field or chemical potential; it can even split and re-form. We discuss how our results relate to recent predictions of hybridizing Majorana fermions in semiconducting nanowires, while considering more mundane explanations.

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We present an experiment designed to determine directly the symmetry of the pairing state in the cuprate superconductors.From the magnetic IIux modulation of YBCO-Pb dc SQUIDs, we determine the spatial anisotropy of the phase of the order parameter in single crystals of YBCO. The experimental results are complicated by SQUID asymmetries and the trapping of magnetic vortices, but taken as ã hole give rather strong evidence for a phase shift of n that is predicted for the d"2 y2 pairing state. This is further corroborated by single junction modulation measurements. PACS numbers: 74.50.+r, 74.20.Mn, 74.72.BkSince the discovery of the high temperature cuprate superconductors, much eflort has concentrated on the determination of the superconducting pairing mechanism and in particular the symmetry of the pairing state. Although many symmetries are allowed in principle [1], there is strong experimental evidence that the spin pairing is singlet [2], suggesting an s-wave or d-wave state. There are also indications that spin fluctuations, thought to be important in the normal state, may also be responsible for the superconductivity.

We present direct evidence for complex p-wave order parameter symmetry and the presence of dynamical chiral order parameter domains of the form px +/- ipy in the ruthenate superconductor Sr2RuO4. The domain structure creates differences in the magnetic field modulation of the critical current of Josephson junctions fabricated on orthogonal faces of Sr2RuO4 single crystals. Transitions between the chiral states of a domain or the motion of domain walls separating them generates telegraph noise in the critical current as a function of magnetic field or time and is responsible for hysteresis observed in field sweeps of the critical current. The presence of such domains confirms the p-wave triplet spin and complex (broken time-reversal symmetry) nature of the superconducting pairing state in Sr2RuO4.

We review the physics of pair density wave (PDW) superconductors. We begin with a macroscopic description that emphasizes order induced by PDW states, such as charge density wave, and discuss related vestigial states that emerge as a consequence of partial meting of the PDW order. We review and critically discuss the mounting experimental evidence for such PDW order in the cuprate superconductors, the status of the theoretical microscopic description of such order, and the current debate on whether the PDW is a "mother order" or another competing order in the cuprates. In addition, we give an overview of the weak coupling version of PDW order, Fulde-Ferrell-Larkin-Ovchinnikov states, in the context of cold atom systems, unconventional superconductors, and non-centrosymmetric and Weyl materials.The GLW energy density consistent with time-reversal, parity, space group, and gauge symmetries is (5, 15)The parameters βi depend upon the specific microscopic model. Depending on which values are found for these, one of five possible ground states can be realized. These five phases include the following: the FF-type phase with only one momentum component, the FF * phase which is a bidirectional version of the FF-type phase, the LO type which include pairing with opposite momentum components: these include the unidirectional phase, and the bidirectional-I (II) phases which have a phase factor of 0 (π/2) between the two unidirectional components. These five states give rise to different patterns of induced order, providing a means to distinguish them. We now turn to these induced orders.Induced Order Parameters www.annualreviews.org • The Physics of Pair Density Waves 3 6 Agterberg et al.

We compute the decoherence caused by 1/f fluctuations at low frequency f in the critical current I0 of Josephson junctions incorporated into flux, phase, charge and hybrid flux-charge superconducting quantum bits (qubits). The dephasing time τ φ scales as I0/ΩΛS 1/2 I 0(1 Hz), where Ω/2π is the energy level splitting frequency, SI 0 (1 Hz) is the spectral density of the critical current noise at 1 Hz, and Λ ≡ |I0dΩ/ΩdI0| is a parameter computed for given parameters for each type of qubit that specifies the sensitivity of the level splitting to critical current fluctuations. Computer simulations show that the envelope of the coherent oscillations of any qubit after time t scales as exp(−t 2 /2τ 2 φ ) when the dephasing due to critical current noise dominates the dephasing from all sources of dissipation. We compile published results for fluctuations in the critical current of Josephson tunnel junctions fabricated with different technologies and a wide range in I0 and A, and show that their values of SI 0 (1 Hz) scale to within a factor of three of 144 (I0/µA) 2 / A/µmWe empirically extrapolate S 1/2 I 0(1 Hz) to lower temperatures using a scaling T (K)/4.2. Using this result, we find that the predicted values of τ φ at 100 mK range from 0.8 to 12 µs, and are usually substantially longer than values measured experimentally at lower temperatures.

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