Violation of emergent rotational symmetry in the hexagonal Kagome superconductor CsVSb.

Superconductivity is caused by electron pairs that are canonically isotropic, whereas some exotic superconductors are known to exhibit non-trivial anisotropy stemming from unconventional pairings. However, superconductors with hexagonal symmetry, the highest rotational symmetry allowed in crystals, exceptionally have strong constraint that is called emergent rotational symmetry (ERS): anisotropic properties should be very weak especially near the critical temperature T even for unconventional pairings such as d-wave states. Here, we investigate superconducting anisotropy of the recently-found hexagonal Kagome superconductor CsVSb, which is known to exhibit various intriguing phenomena originating from its undistorted Kagome lattice formed by vanadium atoms.

In-Plane Magnetic Penetration Depth in Sr_{2}RuO_{4}: Muon-Spin Rotation and Relaxation Study.

We report on measurements of the in-plane magnetic penetration depth (λ_{ab}) in single crystals of Sr_{2}RuO_{4} down to ≃0.015  K by means of muon-spin rotation-relaxation. The linear temperature dependence of λ_{ab}^{-2} for T≲0.

Pines' demon observed as a 3D acoustic plasmon in SrRuO.

The characteristic excitation of a metal is its plasmon, which is a quantized collective oscillation of its electron density. In 1956, David Pines predicted that a distinct type of plasmon, dubbed a 'demon', could exist in three-dimensional (3D) metals containing more than one species of charge carrier. Consisting of out-of-phase movement of electrons in different bands, demons are acoustic, electrically neutral and do not couple to light, so have never been detected in an equilibrium, 3D metal.

Nanoscale Femtosecond Dynamics of Mott Insulator (CaSr)RuO.

CaRuO is a transition-metal oxide that exhibits a Mott insulator-metal transition (IMT) concurrent with a symmetry-preserving Jahn-Teller distortion (JT) at 350 K. The coincidence of these two transitions demonstrates a high level of coupling between the electronic and structural degrees of freedom in CaRuO. Using spectroscopic measurements with nanoscale spatial resolution, we interrogate the interplay of the JT and IMT through the temperature-driven transition.

Keldysh Space Control of Charge Dynamics in a Strongly Driven Mott Insulator.

The fate of a Mott insulator under strong low frequency optical driving conditions is a fundamental problem in quantum many-body dynamics. Using ultrafast broadband optical spectroscopy, we measured the transient electronic structure and charge dynamics of an off-resonantly pumped Mott insulator Ca_{2}RuO_{4}. We observe coherent bandwidth renormalization and nonlinear doublon-holon pair production occurring in rapid succession within a sub-100-fs pump pulse duration.

Unsplit superconducting and time reversal symmetry breaking transitions in SrRuO under hydrostatic pressure and disorder.

There is considerable evidence that the superconducting state of SrRuO breaks time reversal symmetry. In the experiments showing time reversal symmetry breaking, its onset temperature, T, is generally found to match the critical temperature, T, within resolution. In combination with evidence for even parity, this result has led to consideration of a d ± id order parameter.

Superconducting SrRuO Thin Films without Out-of-Phase Boundaries by Higher-Order Ruddlesden-Popper Intergrowth.

Ruddlesden-Popper (RP) phases (O, = 1, 2,···) have attracted intensive research with diverse functionalities for device applications. However, the realization of a high-quality RP-phase film is hindered by the formation of out-of-phase boundaries (OPBs) that occur at terrace edges, originating from lattice mismatch in the -axis direction with the ''O ( = ∞) substrate. Here, using strontium ruthenate RP-phase SrRuO ( = 1) as a model system, an experimental approach for suppressing OPBs was developed.

High-sensitivity heat-capacity measurements on SrRuO under uniaxial pressure.

A key question regarding the unconventional superconductivity of [Formula: see text] remains whether the order parameter is single- or two-component. Under a hypothesis of two-component superconductivity, uniaxial pressure is expected to lift their degeneracy, resulting in a split transition. The most direct and fundamental probe of a split transition is heat capacity.

Uniaxial-strain control of nematic superconductivity in SrBiSe.

Nematic states are characterized by rotational symmetry breaking without translational ordering. Recently, nematic superconductivity, in which the superconducting gap spontaneously lifts the rotational symmetry of the lattice, has been discovered. In nematic superconductivity, multiple superconducting domains with different nematic orientations can exist, and these domains can be controlled by a conjugate external stimulus.

Retraction: In Situ Control of Diamagnetism by Electric Current in Ca_{3}(Ru_{1-x}Ti_{x})_{2}O_{7} [Phys. Rev. Lett. 122, 196602 (2019)].

Retraction of DOI: 10.1103/PhysRevLett.122.

Momentum-resolved superconducting energy gaps of SrRuO from quasiparticle interference imaging.

SrRuO has long been the focus of intense research interest because of conjectures that it is a correlated topological superconductor. It is the momentum space (-space) structure of the superconducting energy gap [Formula: see text] on each band that encodes its unknown superconducting order parameter. However, because the energy scales are so low, it has never been possible to directly measure the [Formula: see text] of SrRuO Here, we implement Bogoliubov quasiparticle interference (BQPI) imaging, a technique capable of high-precision measurement of multiband [Formula: see text] At = 90 mK, we visualize a set of Bogoliubov scattering interference wavevectors [Formula: see text] consistent with eight gap nodes/minima that are all closely aligned to the [Formula: see text] crystal lattice directions on both the α and β bands.

In Situ Control of Diamagnetism by Electric Current in Ca_{3}(Ru_{1-x}Ti_{x})_{2}O_{7}.

Nonequilibrium steady state conditions induced by a dc current can alter the physical properties of strongly correlated electron systems. In this regard, it was recently shown that dc current can trigger novel electronic states, such as current-induced diamagnetism, which cannot be realized in equilibrium conditions. However, reversible control of diamagnetism has not been achieved yet.

Evolution of Superconductivity with Sr-Deficiency in Antiperovskite Oxide SrSnO.

Bulk superconductivity was recently reported in the antiperovskite oxide SrSnO, with a possibility of hosting topological superconductivity. We investigated the evolution of superconducting properties such as the transition temperature T and the size of the diamagnetic signal, as well as normal-state electronic and crystalline properties, with varying the nominal Sr deficiency x. Polycrystalline SrSnO was obtained up to x = 0:6 with a small amount of SrO impurities.

RETRACTED: Current-induced strong diamagnetism in the Mott insulator CaRuO.

Mott insulators can host a surprisingly diverse set of quantum phenomena when their frozen electrons are perturbed by various stimuli. Superconductivity, metal-insulator transition, and colossal magnetoresistance induced by element substitution, pressure, and magnetic field are prominent examples. Here we report strong diamagnetism in the Mott insulator calcium ruthenate (CaRuO) induced by dc electric current.

Strong peak in Tc of Sr2RuO4 under uniaxial pressure.

SrRuO is an unconventional superconductor that has attracted widespread study because of its high purity and the possibility that its superconducting order parameter has odd parity. We study the dependence of its superconductivity on anisotropic strain. Applying uniaxial pressures of up to ~1 gigapascals along a 〈100〉 direction (a axis) of the crystal lattice results in the transition temperature (T) increasing from 1.

Superconductivity in the antiperovskite Dirac-metal oxide SrSnO.

Investigations of perovskite oxides triggered by the discovery of high-temperature and unconventional superconductors have had crucial roles in stimulating and guiding the development of modern condensed-matter physics. Antiperovskite oxides are charge-inverted counterpart materials to perovskite oxides, with unusual negative ionic states of a constituent metal. No superconductivity was reported among the antiperovskite oxides so far.

Compact AC susceptometer for fast sample characterization down to 0.1 K.

We report a new design of an AC magnetic susceptometer compatible with the Physical Properties Measurement System (PPMS) by Quantum Design, as well as with its adiabatic demagnetization refrigerator option. With the elaborate compact design, the susceptometer allows simple and quick sample mounting process. The high performance of the susceptometer down to 0.

Strong increase of T(c) of Sr₂RuO₄ under both tensile and compressive strain.

A sensitive probe of unconventional order is its response to a symmetry-breaking field. To probe the proposed p(x) ± ip(y) topological superconducting state of Sr2RuO4, we have constructed an apparatus capable of applying both compressive and tensile strains of up to 0.23%.

Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4.

Recently, "application of electric field (E-field)" has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature.

Extremely large magnetoresistance in the nonmagnetic metal PdCoO2.

Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO(2). In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35,000% for the field along the [11[over ¯]0] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction.

First-order superconducting transition of Sr2RuO4.

By means of the magnetocaloric effect, we examine the nature of the superconducting-normal (S-N) transition of Sr(2)RuO(4), a most promising candidate for a spin-triplet superconductor. We provide thermodynamic evidence that the S-N transition of this oxide is of first order below approximately 0.8 K and only for magnetic field directions very close to the conducting plane, in clear contrast to the ordinary type-II superconductors exhibiting second-order S-N transitions.

Quantum oscillations and high carrier mobility in the delafossite PdCoO(2).

We present de Haas-van Alphen and resistivity data on single crystals of the delafossite PdCoO(2). At 295 K we measure an in-plane resistivity of 2.6  μΩ cm, making PdCoO(2) the most conductive oxide known.

Edge states of Sr2RuO4 detected by in-plane tunneling spectroscopy.

Tunneling spectroscopy has been performed on Sr(2)RuO(4) searching for the edge states peculiar to topological superconductivity. Conductance spectra exhibit broad humps with three types of peak shape: domelike peak, split peak, and two-step peak. By comparing the experiments with predictions for unconventional superconductivity, these varieties are shown to originate from multiband chiral p-wave symmetry with weak anisotropy of pair amplitude.

Evidence of superconductivity on the border of quasi-2D ferromagnetism in Ca2RuO4 at high pressure.

The layered perovskite Ca(2)RuO(4) is a spin-one Mott insulator at ambient pressure and exhibits metallic ferromagnetism at least up to ∼ 80 kbar with a maximum Curie temperature of 28 K. Above ∼ 90 and up to 140 kbar, the highest pressure reached, the resistivity and ac susceptibility show pronounced downturns below ∼ 0.4 K in applied magnetic fields of up to ∼ 10 mT.