Electronic Specific Heat of La_{2-x}Sr_{x}CuO_{4}: Pseudogap Formation and Reduction of the Superconducting Condensation Energy

To examine the so-called small pseudogap and the superconducting (SC) condensation energy U(0), the electronic specific heat Cel was measured on La_{2-x}Sr_{x}CuO_{4} up to ~120K. In samples with doping level p (=x) less than ~0.2, small pseudogap behavior appears in the \gamma (=Cel/T) vs. T curve around the mean-field critical temperature for a d-wave superconductor Tco (=2*\Delta_{0}/(4~5)k_B), where \Delta_{0} is the maximum gap at T<<Tc. The condensation energy U(0) is largely reduced in the pseudogap regime (p< ~0.2). The reduction of U(0) can be well reproduced by introducing an effective SC energy scale \Delta_{eff}=\beta*p*\Delta_{0} (\beta=4.5) instead of \Delta_{0}. The effective SC energy scale is discussed in relation to the coherent pairing gap formed over the nodal Fermi arc.Comment: 8page

Pseudogap and Superconducting Fluctuation in High-Tc Cuprates: Theory beyond 1-loop Approximation

The pseudogap phenomena induced by the SC fluctuation are investigated in details. We perform a calculation beyond the 1-loop approximation. The SC fluctuation is microscopically derived on the basis of the repulsive Hubbard model. The vertex corrections are collected in the infinite order with use of the quasi-static approximation. The single-particle excitations, NMR 1/T_{1}T, spin susceptibility and superconducting transition temperature are discussed. The important role of the vertex correction is pointed out for the single particle spectral function. On the other hand, the validity of the 1-loop order theory is confirmed for other quantities. We shed light on the essential nature of SC fluctuation leading to the pseudogap from the comparison with spin and charge fluctuations

Strong-coupling Superconductivity in the Cuprate Oxide

Superconductivity in the cuprate oxide is studied by Kondo-lattice theory based on the t-J model with the el-ph interaction arising from the modulation of the superexchange interaction by phonons. The self-energy of electrons is decomposed into the single-site and multisite ones. It is proved by using the mapping of the single-site one in the t-J model to its corresponding one in the Anderson model that the single-site self-energy is that of a normal Fermi liquid, even if a superconducting (SC) order parameter appears or the multisite one is anomalous. The electron liquid characterized by the single-site self-energy is a normal Fermi liquid. The Fermi liquid is further stabilized by the RVB mechanism. The stabilized Fermi liquid is a relevant unperturbed state that can be used to study superconductivity and anomalous Fermi-liquid behaviors. The so-called spin-fluctuation-mediated exchange interaction, which includes the superexchange interaction as a part, is the attractive interaction that binds d-wave Cooper pairs. An analysis of the spin susceptibility implies that, because of the el-ph interaction, the imaginary part of the exchange interaction has a sharp peak or dip at \pm\omega^*, where \omega^*\simeq \omega_ph in the normal state and \epsilon_G/2 \lessim \omega^* \lessim \epsilon_G /2+ \omega_ph in the SC state, where \omega_ph is the energy of relevant phonons and \epsilon_G is the SC gap. If the imaginary part has a sharp peak or dip at \pm\omega^*, the dispersion relation of quasi-particles has kink structures near \pm\omega^* above and below the chemical potential, the density of states has dip-and-hump structures near \pm \omega^* outside the coherence peaks in the SC state, and the anisotropy of the gap deviates from the simple d-wave anisotropy.Comment: 19 pages, 12 figure

Outcomes and practice patterns of medical management of blunt thoracic aortic injury from the Aortic Trauma Foundation global registry

Objective: Blunt thoracic aortic injury (BTAI) is the second leading cause of death from blunt trauma. In the present study, we aimed to determine the outcomes of medical management (MM) for BTAI. We hypothesized from the results of several previously reported studies, that patients with a minimal aortic injury (BTAI grades 1 and 2) could safely be treated with definitive MM alone. Methods: The Aortic Trauma Foundation international prospective multicenter registry was used to examine the demographics, injury characteristics, management, and outcomes of patients with BTAI. We analyzed a subset of patients for whom MM was initiated as definitive therapy. Results: From November 2016 to April 2020, 432 patients (median age, 41 years; 76% male; median injury severity score, 34) with BTAI (Society for Vascular Surgery grade 1, 23.6%; grade 2, 14.4%; grade 3, 51.2%; grade 4, 10.9%) were evaluated. Of the 432 patients, 245 (57%) had received MM in the initial period and 114 (26.4%) had received MM as the planned definitive therapy (grade 1, 59.6%; grade 2, 23.7%; grade 3, 15.8%; grade 4, 0.9%). The most common mechanism of BTAI was a motor vehicle collision (60.4%). Hypotension was present on arrival in 74 patients (17.2%). Continuous titratable infusion of antihypertensive medication was used for 49.1%, followed by intermittent bolus administration (29.8%), with beta-blockers (74.6%) the most common agent used. Treatments were targeted to a goal systolic blood pressure for 83.3%, most often to a target goal systolic blood pressure &lt;120 mm Hg (66.3%). The MM goals based on blood pressure control were attained in 64.0% (73 of 114). Twelve patients (10.5%; grade 1, 1; grade 2, 0; grade 3, 10; grade 4, 1) had required subsequent intervention after MM. Eleven patients (9.6%) had undergone thoracic endovascular aortic repair and one (0.9%) had required open repair for a grade 4 injury. The overall in-hospital mortality for patients selected for definitive MM was 7.9%. No aortic-related deaths had occurred in the patients receiving definitive MM. Conclusions: Approximately one in four patients with BTAI will receive MM as definitive therapy. The variation in the pharmacologic therapies used is considerable. MM for patients with minimal aortic injury (BTAI grades 1 and 2) is safe and effective, with a low overall intervention rate and no aortic-related deaths. These findings support the use of definitive MM for grade 2 BTAI

Energy gaps in high-transition-temperature cuprate superconductors

The spectral energy gap is an important signature that defines states of quantum matter: insulators, density waves, and superconductors have very different gap structures. The momentum resolved nature of angle-resolved photoemission spectroscopy (ARPES) makes it a powerful tool to characterize spectral gaps. ARPES has been instrumental in establishing the anisotropic d-wave structure of the superconducting gap in high-transition temperature (Tc) cuprates, which is different from the conventional isotropic s-wave superconducting gap. Shortly afterwards, ARPES demonstrated that an anomalous gap above Tc, often termed the pseudogap, follows a similar anisotropy. The nature of this poorly understood pseudogap and its relationship with superconductivity has since become the focal point of research in the field. To address this issue, the momentum, temperature, doping, and materials dependence of spectral gaps have been extensively examined with significantly improved instrumentation and carefully matched experiments in recent years. This article overviews the current understanding and unresolved issues of the basic phenomenology of gap hierarchy. We show how ARPES has been sensitive to phase transitions, has distinguished between orders having distinct broken electronic symmetries, and has uncovered rich momentum and temperature dependent fingerprints reflecting an intertwined & competing relationship between the ordered states and superconductivity that results in multiple phenomenologically-distinct ground states inside the superconducting dome. These results provide us with microscopic insights into the cuprate phase diagram.Comment: A review article for ARPES studies on high-Tc cuprates. 6 figure