Multiband superconductivity with unexpected deficiency of nodal quasiparticles in CeCu2Si2

Superconductivity in the heavy-fermion compound CeCu2Si2 is a prototypical example of Cooper pairs formed by strongly correlated electrons. For more than 30 years, it has been believed to arise from nodal d-wave pairing mediated by a magnetic glue. Here, we report a detailed study of the specific heat and magnetization at low temperatures for a high-quality single crystal. Unexpectedly, the specific-heat measurements exhibit exponential decay with a two-gap feature in its temperature dependence, along with a linear dependence as a function of magnetic field and the absence of oscillations in the field angle, reminiscent of multiband full-gap superconductivity. In addition, we find anomalous behavior at high fields, attributed to a strong Pauli paramagnetic effect. A low quasiparticle density of states at low energies with a multiband Fermi-surface topology would open a new door into electron pairing in CeCu2Si2.Comment: 5 pages, 4 figures (main text) + 5 pages, 6 figures (supplemental material), published in Phys. Rev. Let

Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2

This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconductor CeCu$_2$Si$_2$ ($T_{\rm c} \sim 0.6$ K). We discuss the superconducting gap structure and the origin of the anomalous pair-breaking phenomena, leading e.g., to the suppression of the upper critical field $H_{\rm c2}$, found in the high-field region. The data show that the anomalous pair breaking becomes prominent below about 0.15 K in any field direction, but occurs closer to $H_{\rm c2}$ for $H \parallel c$. The presence of this anomaly is confirmed by the fact that the specific-heat and magnetization data satisfy standard thermodynamic relations. Concerning the gap structure, field-angle dependences of the low-temperature specific heat within the $ab$ and $ac$ planes do not show any evidence for gap nodes. From microscopic calculations in the framework of a two-band full-gap model, the power-law-like temperature dependences of $C$ and $1/T_1$, reminiscent of nodal superconductivity, have been reproduced reasonably. These facts further support multiband full-gap superconductivity in CeCu$_2$Si$_2$.Comment: 10 pages, 8 figures, published in Phys. Rev.

Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material

Optical control of crystal structures is a promising route to change physical properties including topological nature of a targeting material. Time-resolved X-ray diffraction measurements using the X-ray free-electron laser are performed to study the ultrafast lattice dynamics of VTe$_2$, which shows a unique charge-density-wave (CDW) ordering coupled to the topological surface states as a first-order phase transition. A significant oscillation of the CDW amplitude mode is observed at a superlattice reflection as well as Bragg reflections. The frequency of the oscillation is independent of the fluence of the pumping laser, which is prominent to the CDW ordering of the first-order phase transition. Furthermore, the timescale of the photoinduced 1$T^{\prime\prime}$ to 1$T$ phase transition is independent of the period of the CDW amplitude mode

当科が報告したインシデントレポートの分析

当院では 2010年7月からコンピューターを用いたインシデント報告システムを導入し,職員が匿名でインシデントを報告できる体制となっている.本体制運用開始後10年間に当科で報告されたインシデントレポート55件を患者影響レベルに従って8段階に分類した.レベル0は6件(10.9%),レベル1は14件 (25.5%),レベル2は13件(23.6%),レベル 3a は10件(18.2%),レベル3bは8件(14.5%),レベル4aは0件(0%),レベ4bは3件(5.4%),レベ5は1 件(1.8%)であった.当科におけるレベル別報告件数の比率は，重大なアクシデントと中等度のエラーと300のヒヤリ・ハットの比率が1：29：300であるというハインリッヒの法則に則っていなかった.しかし当科では2010年から2020年にかけてヒヤリ・ハット報告数は増加しているため,インシデントを報告する習慣が身につきつつあると考えられた.今後,より積極的に報告を行うように，職員へのさらなる啓蒙活動が医療事故の防止のために重要であると考えられた.In July 2010,we introduced a computerized incident reporting system, which allows staff to report incidents anonymously. The 55 incidents reported in our department during the first 10 years of operation of this system were classified into 8 levels according to the patient impact level. Level 0 was 6 incidents (10.9%),level 1 was 14 incidents (25.5%),level 2 was 13 incidents (23.6%),level 3a was 10 incidents (18.2%),level 3b was 8 incidents (14.5%),level 4a was 0 incidents (0%),level 4b was 3 incidents (5.4%),and level 5 was 1 incident (1.8%).The ratio of the number of reports by level in our department did not follow Heinrich\u27s law, which states that the ratio of serious incidents to moderate errors and 300 near-misses is 1:29:300.However,the number of Hiyari-Hatto reports increased from 2010 to 2020 in our department, suggesting that the habit of reporting incidents is becoming more common. In the future, it will be important to educate the staff to report more actively in order to prevent medical accidents