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Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.

Fermi surfaces in superconductivity Recent quantum oscillation experiments on high transition temperature ( T c ) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Sebastian et al . report experiments on YBa 2 Cu 3 O 6.51 that reveal more than one carrier pocket. They find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Experiments on YBa 2 Cu 3 O 6.51 reveal more than one carrier pocket, and evidence is found for the existence of a much larger pocket of heavier mass carriers having a thermodynamically dominant role in this hole-doped superconductor. To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing 1 , 2 , 3 , 4 , 5 , 6 . Recent quantum oscillation experiments on high-transition-temperature (high- T c ) copper oxide superconductors 7 , 8 , 9 , 10 have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization 11 . The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d -wave superconductivity 12 , 13 , 14 , 15 . Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa 2 Cu 3 O 6.51 that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.

Since the discovery of superconductivity 1 , there has been a drive to understand the mechanisms by which it occurs. The BCS (Bardeen–Cooper–Schrieffer) model successfully treats the electrons in conventional superconductors as pairs coupled by phonons (vibrational modes of oscillation) moving through the material 2 , but there is as yet no accepted model for high-transition-temperature, organic or ‘heavy fermion’ superconductivity. Experiments that reveal unusual properties of those superconductors could therefore point the way to a deeper understanding of the underlying physics. In particular, the response of a material to a magnetic field can be revealing, because this usually reduces or quenches superconductivity. Here we report measurements of the heat capacity and magnetization that show that, for particular orientations of an external magnetic field, superconductivity in the heavy-fermion material CeCoIn 5 is enhanced through the magnetic moments (spins) of individual electrons. This enhancement occurs by fundamentally altering how the superconducting state forms, resulting in regions of superconductivity alternating with walls of spin-polarized unpaired electrons; this configuration lowers the free energy and allows superconductivity to remain stable. The large magnetic susceptibility of this material leads to an unusually strong coupling of the field to the electron spins, which dominates over the coupling to the electron orbits.

The nature of the Fermi surface observed in the recently discovered family of unconventional insulators starting with SmB6 is a subject of intense inquiry. Here we shed light on this question by accessing quantum oscillations in the high magnetic field-induced metallic regime above ≈47 T in YbB12, which we compare with the unconventional insulating regime. In the field-induced metallic regime, we find prominent quantum oscillations in the electrical resistivity characterised by multiple frequencies and heavy effective masses. The close similarity in Lifshitz-Kosevich low-temperature growth of quantum oscillation amplitude in insulating YbB12 to field-induced metallic YbB12, points to an origin of quantum oscillations in insulating YbB12 from in-gap neutral low energy excitations. Higher frequency Fermi surface sheets of heavy quasiparticle effective mass emerge in the field-induced metallic regime of YbB12 in addition to multiple heavy Fermi surface sheets observed in both insulating and metallic regimes. f-electron hybridisation is thus observed to persist from the unconventional insulating to the field-induced metallic regime of YbB12, in contrast to the unhybridised conduction electron Fermi surface observed in unconventional insulating SmB6. Our findings thus require an alternative model for YbB12, of neutral in-gap low energy excitations, wherein the f-electron hybridisation is retained.

Numerous phenomenological parallels have been drawn between f - and d - electron systems in an attempt to understand their display of unconventional superconductivity. The microscopics of how electrons evolve from participation in large moment antiferromagnetism to superconductivity in these systems, however, remains a mystery. Knowing the origin of Cooper paired electrons in momentum space is a crucial prerequisite for understanding the pairing mechanism. Of special interest are pressure-induced superconductors CeIn 3 and CeRhIn 5 in which disparate magnetic and superconducting orders apparently coexist—arising from within the same f -electron degrees of freedom. Here, we present ambient pressure quantum oscillation measurements on CeIn 3 that crucially identify the electronic structure—potentially similar to high-temperature superconductors. Heavy hole pockets of f -character are revealed in CeIn 3 , undergoing an unexpected effective mass divergence well before the antiferromagnetic critical field. We thus uncover the softening of a branch of quasiparticle excitations located away from the traditional spin fluctuation-dominated antiferromagnetic quantum critical point. The observed Fermi surface of dispersive f -electrons in CeIn 3 could potentially explain the emergence of Cooper pairs from within a strong moment antiferromagnet.

BackgroundInfluenza vaccination (FV) is recommended for patients with cancer. Recent data suggested that the administration of the FV was associated with an increase in immune-related adverse events (irAEs) among patients on immune checkpoint inhibitors (ICIs). Myocarditis is an uncommon but serious complication of ICIs and may also result from infection with influenza. There are no data testing the relationship between FV and the development of myocarditis on ICIs.MethodsPatients on ICIs who developed myocarditis (n = 101) (cases) were compared to ICI-treated patients (n = 201) without myocarditis (controls). A patient was defined as having the FV if they were administered the FV from 6 months prior to start of ICI to anytime during ICI therapy. Alternate thresholds for FV status were also tested. The primary comparison of interest was the rate of FV between cases and controls. Patients with myocarditis were followed for major adverse cardiac events (MACE), defined as the composite of cardiogenic shock, cardiac arrest, hemodynamically significant complete heart block and cardiovascular death.ResultsThe FV was administered to 25% of the myocarditis cases compared to 40% of the non-myocarditis ICI-treated controls (p = 0.01). Similar findings of lower rates of FV administration were noted among myocarditis cases when alternate thresholds were tested. Among the myocarditis cases, those who were vaccinated had 3-fold lower troponin levels when compared to unvaccinated cases (FV vs. No FV: 0.12 [0.02, 0.47] vs. 0.40 [0.11, 1.26] ng/ml, p = 0.02). Within myocarditis cases, those administered the FV also had a lower rate of other irAEs when compared to unvaccinated cases (36 vs. 55% p = 0.10) including lower rates of pneumonitis (12 vs. 36%, p = 0.03). During follow-up (175 [IQR 89, 363] days), 47% of myocarditis cases experienced a MACE. Myocarditis cases who received the FV were at a lower risk of cumulative MACE when compared to unvaccinated cases (24 vs. 59%, p = 0.002).ConclusionThe rate of FV among ICI-related myocarditis cases was lower than controls on ICIs who did not develop myocarditis. In those who developed myocarditis related to an ICI, there was less myocardial injury and a lower risk of MACE among those who were administered the FV.

Our principle objective was to examine the personal and professional impact of service user (SU) suicide on mental health professionals (MHPs). We also wished to explore putative demographic or clinical factors relating to SUs or MPHs that could influence the impact of SU suicide for MHPs and explore factors MHPs report as helpful in reducing distress following SU suicide. A mixed-method questionnaire with quantitative and thematic analysis was utilised. Quantitative data indicated SU suicide was associated with personal and professional distress with sadness (79.5%), shock (74.5%) and surprise (68.7%) particularly evident with these phenomena lasting less than a year for more than 90% of MHPs. MHPs also reported guilt, reduced self-confidence and a fear of negative publicity. Thematic analysis indicated that some MHPs had greater expertise when addressing SU suicidal ideation and in supporting colleagues after experiencing a SU suicide. Only 17.7% of MHPs were offered formal support following SU suicide. SU suicide impacts MHPs personally and professionally in both a positive and negative fashion. A culture and clear pathway of formal support for MHPs to ascertain the most appropriate individualised support dependent on the distress they experience following SU suicide would be optimal.

Central retinal venous occlusion usually occurs in elderly patients with known risk factors such as raised intraocular pressure, arterial hypertension, atherosclerotic disease, or diabetes mellitus. [...]central retinal venous occlusion infrequently occurs in individuals with hyperviscosity from leukaemia, polycythaemia, Waldenstrom's macroglobulinaemia, sickle cell disease, and periphlebitis. 1 However, it has also been described in patients with antiphospholipid antibodies 2 and rarely in patients with thrombotic thrombocytopenic purpura (TTP) (pentad of fever, microangiopathic haemolytic anaemia, thrombocytopenia, neurological abnormalities, and renal impairment).