An external magnetic field can induce a transition in α-RuCl3 from an ordered zigzag state to a disordered state that is possibly related to the Kitaev quantum spin liquid. Here we present new field dependent inelastic neutron scattering and magnetocaloric effect measurements implying the existence of an additional transition out of the quantum spin liquid phase at an upper field limit Bu. The neutron scattering shows three distinct regimes of magnetic response. In the low field ordered state the response shows magnon peaks; the intermediate field regime shows only continuum scattering, and above Bu the response shows sharp magnon peaks at the lower bound of a strong continuum. Measurable dispersion of magnon modes along the (0, 0, L) direction implies non-negligible inter-plane interactions. Combining the magnetocaloric effect measurements with other data a T − B phase diagram is constructed. The results constrain the range where one might expect to observe quantum spin liquid behavior in α-RuCl3. arXiv:1903.00056v3 [cond-mat.str-el]

We introduce a log-gas model that is a generalization of a random matrix ensemble with an additional interaction, whose strength depends on a parameter γ. The equilibrium density is computed by numerically solving the Riemann-Hilbert problem associated with the ensemble. The effect of the additional parameter γ associated with the two-body interaction can be understood in terms of an effective γ-dependent single-particle confining potential.

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In the search of topological superconductors, nailing down the Fermiology of the normal state is as crucial a prerequisite as unraveling the superconducting pairing symmetry. In particular, the number of time-reversal-invariant momenta (TRIM) in the Brillouin zone enclosed by Fermi surfaces is closely linked to the topological class of time-reversal-invariant systems, and can experimentally be investigated. We report here a detailed study of de Haas van Alphen quantum oscillations in single crystals of the topological semimetal CaSn3 with torque magnetometry in high magnetic fields up to 35 T. In conjunction with density functional theory based calculations, the observed quantum oscillations frequencies indicate that the Fermi surfaces of CaSn3 enclose an odd number of TRIM, satisfying one of the proposed criteria to realize topological superconductivity. Nonzero Berry phases extracted from the magnetic oscillations also support the nontrivial topological nature of CaSn3.

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We consider a limiting case of the joint probability distribution for a random matrix ensemble with an additional interaction term controlled by an exponent γ (called the γ-ensembles), which is equivalent to the probability distribution of Laguerre β-ensembles. The effective potential, which is essentially the confining potential for an equivalent ensemble with γ = 1 (called the Muttalib-Borodin ensemble), is a crucial quantity defined in solution to the Riemann-Hilbert problem associated with the γ-ensembles. It enables us to numerically compute the eigenvalue density of Laguerre β-ensembles for all β > 1. In addition, the effective potential shows a non-monotonic behavior for γ < 1, suggestive of its possible role in developing a transition from a diverging to a non-diverging density near the hard-edge of the eigenvalue spectrum. Such a transition in eigenvalue density is of critical importance for the random matrix theory describing disordered mesoscopic systems. For γ-ensembles with γ > 1, the effective potential also shows transition from non-monotonic to monotonic behavior near the origin when a parameter of the additional interaction term is varied.

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