Moving Dirac nodes by chemical substitution.

Dirac fermions play a central role in the study of topological phases, for they can generate a variety of exotic states, such as Weyl semimetals and topological insulators. The control and manipulation of Dirac fermions constitute a fundamental step toward the realization of novel concepts of electronic devices and quantum computation. By means of Angle-Resolved Photo-Emission Spectroscopy (ARPES) experiments and ab initio simulations, here, we show that Dirac states can be effectively tuned by doping a transition metal sulfide, [Formula: see text], through Co/Ni substitution. The symmetry and chemical characteristics of this material, combined with the modification of the charge-transfer gap of [Formula: see text] across its phase diagram, lead to the formation of Dirac lines, whose position in k-space can be displaced along the [Formula: see text] symmetry direction and their form reshaped. Not only does the doping x tailor the location and shape of the Dirac bands, but it also controls the metal-insulator transition in the same compound, making [Formula: see text] a model system to functionalize Dirac materials by varying the strength of electron correlations.

Two-Fluid Coexistence in a Spinless Fermions Chain with Pair Hopping.

We show that a simple one-dimensional model of spinless fermions with pair hopping displays a phase in which a Luttinger liquid of paired fermions coexists with a Luttinger liquid of unpaired fermions. Our results are based on extensive numerical density-matrix renormalization-group calculations and are supported by a two-fluid model that captures the essence of the coexistence region.

Superradiant Phase Transition in Electronic Systems and Emergent Topological Phases.

We derive a general criterion for determining the onset of superradiant phase transition in electronic bands coupled to a cavity field, with possibly electron-electron interactions. For longitudinal superradiance in 2D or genuine 1D systems, we prove that it is always prevented, thereby extending existing no-go theorems. Instead, a superradiant phase transition can occur to a nonuniform transverse cavity field and we give specific examples in noninteracting models, either through Fermi surface nesting or parabolic band touching. Investigating the resulting time-reversal symmetry breaking superradiant states, we find in the former case Fermi surface lifting down to four Dirac points on a square lattice model, with topologically protected zero modes, and in the latter case topological bands with nonzero Chern number on an hexagonal lattice.

Unveiling Odd-Frequency Pairing around a Magnetic Impurity in a Superconductor.

We study the unconventional superconducting correlations caused by a single isolated magnetic impurity in a conventional s-wave superconductor. Because of the local breaking of time-reversal symmetry, the impurity induces unconventional superconductivity, which is even in both space and spin variables but odd under time inversion. We derive an exact proportionality relation between the even-frequency component of the local electron density of states and the imaginary part of the odd-frequency local pairing function. By applying this relation to scanning tunneling microscopy spectra taken on top of magnetic impurities immersed in a Pb/Si(111) monolayer, we show experimental evidence of the occurrence of the odd-frequency pairing in these systems and explicitly extract its superconducting function from the data.

Characterization of a Low-Cost Plastic Fiber Array Detector for Proton Beam Dosimetry.

The Pencil Beam Scanning (PBS) technique in proton therapy uses fast magnets to scan the tumor volume rapidly. Changing the proton energy allows changing to layers in the third dimension, hence scanning the same volume several times. The PBS approach permits adapting the speed and/or current to modulate the delivered dose. We built a simple prototype that measures the dose distribution in a single step. The active detection material consists of a single layer of scintillating fibers (i.e., 1D) with an active length of 100 mm, a width of 18.25 mm, and an insignificant space (20 µm) between them. A commercial CMOS-based camera detects the scintillation light. Short exposure times allow running the camera at high frame rates, thus, monitoring the beam motion. A simple image processing method extracts the dose information from each fiber of the array. The prototype would allow scaling the concept to multiple layers read out by the same camera, such that the costs do not scale with the dimensions of the fiber array. Presented here are the characteristics of the prototype, studied under two modalities: spatial resolution, linearity, and energy dependence, characterized at the Center for Proton Therapy (Paul Scherrer Institute); the dose rate response, measured at an electron accelerator (Swiss Federal Institute of Metrology).

Braiding of Majorana Fermions in a Cavity.

We study the dynamical process of braiding Majorana bound states (MBS) in the presence of the coupling to photons in a microwave cavity. We show theoretically that the π/4 phase associated with the braiding of MBS, as well as the parity of the ground state are imprinted into the photonic field of the cavity, which can be detected by dispersive readout techniques. These manifestations are purely dynamical, they occur in the absence of any splitting of the MBS that are exchanged, and they disappear in the static setups studied previously. Conversely, the cavity can affect the braiding phase, which in turn should allow for cavity controlled braiding.

Proposal for a quantum magnetic RC circuit.

We propose a setup that is the spin analog of the charge-based quantum RC circuit. We define and compute the spin capacitance and the spin resistance of the circuit for both ferromagnetic and antiferromagnetic systems. We find that the antiferromagnetic setup has universal properties, but the ferromagnetic setup does not. We discuss how to use the proposed setup as a quantum source of spin excitations, and put forward two possible experimental realizations, using either ultracold atoms in optical lattices or artificially engineered atomic-spin chains.

Interplay between classical magnetic moments and superconductivity in quantum one-dimensional conductors: toward a self-sustained topological Majorana phase.

We study a one-dimensional interacting electronic liquid coupled to a 1D array of classical magnetic moments and to a superconductor. We show that at low energy and temperature the magnetic moments and the electrons become strongly entangled and that a magnetic spiral structure emerges. For strong enough coupling between the electrons and magnetic moments, the 1D electronic liquid is driven into a topological superconducting phase supporting Majorana fermions without any fine-tuning of external parameters. Our analysis applies at low enough temperature to a quantum wire in proximity to a superconductor when the hyperfine interaction between electrons and nuclear spins is taken into account, or to a chain of magnetic adatoms adsorbed on a superconducting surface.

Ultra-low power high temperature and radiation hard complementary metal-oxide-semiconductor (CMOS) silicon-on-insulator (SOI) voltage reference.

This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of -40-200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage V(REF) depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 µW at room temperature and only 75 µW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of V(REF) and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2.

Spin and Majorana polarization in topological superconducting wires.

We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit coupling (SOC), which supports Majorana fermions when subject to a Zeeman magnetic field and in the proximity of a superconductor. Using both analytical and numerical techniques we calculate the electronic spin texture of the Majorana end states. We find that the spin polarization of these states depends on the relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we define and calculate a local "Majorana polarization" and "Majorana density" and argue that they can be used as order parameters to characterize the topological transition between the trivial system and the system exhibiting Majorana bound modes. We find that the local Majorana polarization is correlated to the transverse spin polarization, and we propose to test the presence of Majorana fermions in a 1D system by a spin-polarized density of states measurement.

Tunable Kondo effect in a double quantum dot coupled to ferromagnetic contacts.

We investigate the effects induced by ferromagnetic contacts attached to a serial double quantum dot. Spin polarization generates effective magnetic fields and suppresses the Kondo effect in each dot. The superexchange interaction J(AFM), tuned by the interdot tunneling rate t, can be used to compensate the effective fields and restore the Kondo resonance when the contact polarizations are aligned. As a consequence, the direction of the spin conductance can be controlled and even reversed using electrostatic gates alone. Our results demonstrate a new approach for controlling spin-dependent transport in carbon nanotube double dot devices.

Majorana edge states in interacting one-dimensional systems.

We show that one-dimensional electron systems in the proximity of a superconductor that support Majorana edge states are extremely susceptible to electron-electron interactions. Strong interactions generically destroy the induced superconducting gap that stabilizes the Majorana edge states. For weak interactions, the renormalization of the gap is nonuniversal and allows for a regime in which the Majorana edge states persist. We present strategies of how this regime can be reached.

Disordered one-dimensional bose-fermi mixtures: the Bose-Fermi glass.

We analyze an interacting Bose-Fermi mixture in a 1D disordered potential by using a combination of renormalization group and variational methods. We obtain the complete phase diagram in the incommensurate case as a function of bosonic and interspecies interaction strengths, in the weak disorder limit. We find that the system is characterized by several phase transitions between superfluid and various glassy insulating states, including a new Bose-Fermi glass phase, where both species are coupled and localized. We show that the dynamical structure factor, as measured through Bragg scattering experiments, can distinguish between the various localized phases and probe their dynamics.

Isolated pairs of Majorana zero modes in a disordered superconducting lead monolayer.

Majorana zero modes are fractional quantum excitations appearing in pairs, each pair being a building block for quantum computation. Some signatures of Majorana zero modes have been reported at endpoints of one-dimensional systems, which are however required to be extremely clean. An alternative are two-dimensional topological superconductors, such as the Pb/Co/Si(111) system shown recently to be immune to local disorder. Here, we use scanning tunneling spectroscopy to characterize a disordered superconducting monolayer of Pb coupled to underlying Co-Si magnetic islands. We show that pairs of zero modes are stabilized: one zero mode positioned in the middle of the magnetic domain and its partner extended all around the domain. The zero mode pair is remarkably robust, isolated within a hard superconducting gap. Our theoretical scenario supports the protected Majorana nature of this zero mode pair, highlighting the role of magnetic or spin-orbit coupling textures.

[Prospective evaluation of the effects of a practical introduction to urology session on the recruitment of urology intern in Paris: final results]. / Evaluation prospective des effets du stage d'initiation pratique sur le recrutement des internes d'urologie 'a Paris: résultats définitifs.

OBJECTIVES: To evaluate the effects of a practical introduction to urology session on the recruitment of Parisian interns since introduction of the National Classifying Examination. MATERIALS AND METHODS: Since 2004, all surgery interns appointed in Paris have participated in a practical introduction to urology session before starting work in hospital. They were asked to complete a questionnaire. The prospective survey studied: age, gender, urology training as a medical student and the intern's preferences in relation to 11 surgical specialties. Interns were recontacted annually to determine their choice of specialization. RESULTS: Population. 255 interns participated, including 145 females (56.9%) and 110 males (43.1%). The mean age was 24.6 +/- 5 years (range: 22-31). 173 interns were attached to a Parisian teaching hospital (67.8%) and 82 (32.2%) were attached to a provincial teaching hospital. 52 interns (21.2%) had completed at least one attachment in a urology department during their medical training. Surgical specialties. Orthopaedics was most frequently listed (n = 48 ; 28.9%). Urology was chosen by 32 interns (12.5%), 28 of whom had completed an urology attachment during their medical training. At the end of the introductory training sessions, 18 interns were tempted by urology. At one year, 31/34 interns (91.2%) confirmed their choice in favour of urology. CONCLUSION: A practical training sessions very early in the training of young surgeons is a good solution to introduce them to urology. Based on a more informed choice, the most motivated interns are encouraged to preferentially choose this discipline.

Two-dimensional topological superconductivity in Pb/Co/Si(111).

Just like insulators can present topological phases characterized by Dirac edge states, superconductors can exhibit topological phases characterized by Majorana edge states. In particular, one-dimensional topological superconductors are predicted to host zero-energy Majorana fermions at their extremities. By contrast, two-dimensional superconductors have a one-dimensional boundary which would naturally lead to propagating Majorana edge states characterized by a Dirac-like dispersion. In this paper we present evidences of one-dimensional dispersive in-gap edge states surrounding a two-dimensional topological superconducting domain consisting of a monolayer of Pb covering magnetic Co-Si islands grown on Si(111). We interpret the measured dispersive in-gap states as a spatial topological transition with a gap closure. Our method could in principle be generalized to a large variety of heterostructures combining a Rashba superconductor with a magnetic layer in order to be used as a platform for engineering topological quantum phases.

[How to anticipate specialization at the Examen National Classant (National Entrance Examination) to encourage interns to choose urology]. / Comment anticiper la filiarisation à l'Examen National Classant pour motiver les internes vers l'urologie?

OBJECTIVES: To analyse the value of an introduction to urology session to recruit interns following the Examen National Classant (ENC) (National Entrance Examination). MATERIALS AND METHODS: Over a 2-year period, interns appointed to surgery in Paris participated in a one-day introduction to urology session before starting work as surgical interns. A questionnaire at the beginning of internship recorded: age, gender, teaching hospital, student attachment in urology and desired specialization as a function of the surgical training programmes proposed by the ENC. Items concerning the desired specialization were resubmitted to the interns at the end of the session. RESULTS: Population. 166 interns, 98 females (59%) and 68 males (41%) with a mean age of 24.8 +/- 5 years (range: 22-31) participated in this study. 110 interns had trained at a Parisian teaching hospital (66.2%) and 56 (33.8%) had trained at a provincial teaching hospital. 31 interns (18.7%) had completed at least one urology attachment during their medical training. Desired specialization: Orthopaedics was the discipline most frequently cited (n=48; 28.9%). Urology was selected by 19 interns (11.4%), 17 of whom had completed an urology attachment during their medical training. At the end of the introduction to urology session, another 15 interns initially oriented towards other specializations were interested in urology training. CONCLUSION: Specialization of certain surgical disciplines during internship could become inevitable in the medium term. In this case, the organization of national introduction to urology sessions in each ENC allocation region would be a solution to encourage motivated interns to immediately choose urology as their surgical speciality by preference rather than by default.

[Results of the AMS 800 artificial urinary sphincter in men, based on a series of 47 patients]. / Résultats du sphincter urinaire artificiel AMS 800 chez l'homme: à propos d'une série de 47 patients.

INTRODUCTION: Male urinary incontinence due to sphincter incompetence is usually secondary to prostate surgery. After failure of other treatments, severe sphincter incompetence requires placement of an artificial urinary sphincter The authors present the results of the AMS 800 artificial urinary sphincter based on a series of 47 consecutively operated patients. PATIENTS AND METHODS: From 1990 to 2003, 47 AMS 800 were inserted by the same operator and according to the same technique. The aetiologies of urinary incontinence were: radical prostatectomy (45% of cases), transurethral resection of the prostate (36%), open prostatectomy (10.5%), and others (8.5%). RESULTS: The mean age of the patients was 65 years. The mean follow-up was 36 months. The mean time to insertion was 3 years and 10 months (range: 5 months-15 years). 23.4% of patients presented one or several complications (mechanical failure: 19%; infection; 10.6%; erosion: 4%; bladder stones: 2%), 21% of patients required one or several surgical revisions after a mean interval of 25.5 months (range: 2-80 months). The actuarial 5-year revision rate was 25.5%. With a mean follow-up of 36 months, 98% of patients had a functioning artificial urinary sphincter and 83% still had their original artificial urinary sphincter Social continence and patient satisfaction rates were 87% and 95.7%, respectively. CONCLUSION: These results are comparable to those of similar published series. The AMS 800 is associated with high continence and patient satisfaction rates and currently remains the reference treatment for refractory sphincter incompetence in men.

[Improvement of the recruitment of surgery interns derived from the Epreuves Nationales Classantes (National-Ranking Exam): practical solution applied to urology]. / Amélioration du recrutement des internes de chirurgie issus des Epreuves Nationales Classantes: solution pratique appliquée a la filière urologique.

OBJECTIVES: To analyse the value of an urology initiation session proposed to young interns to improve recruitment of the discipline since the introduction of the new National-Ranking Exam (NRE). MATERIALS AND METHODS: In October 2004, the 77 interns appointed to surgery in Paris on the basis of the ENC participated in a one-day urology initiation session organized by the AFUF, at the AP-HP School of Surgery. All interns were given a questionnaire at the beginning of the session to record the following data: age, gender, teaching hospital, a student attachment in urology and desired specialization as a function of the surgical training programmes proposed by the ENC. Items concerning the desired specialization were resubmitted to the interns at the end of the session. RESULTS: Population. 77 interns, 48 females (62.3%) and 29 males (37.7%) with a mean age of 25.2 +/- 5 years (range: 23-31). 55 interns had trained at a Parisian teaching hospital (67%) and 22 (28.6%) had trained at a provincial teaching hospital. 16 interns (20.8%) had completed at least one urology attachment during their medical training. Desired specialization. Orthopaedics was the discipline most frequently cited (n = 20; 26%). Urology was chosen by 8 interns (10.40%), who had all completed an urology attachment during their medical training. At the end of the urology initiation session, another 8 interns expressed the desire to specialize in urology. Of the 16 potential urology interns, 9 (56.2%) confirmed that their decision was final. CONCLUSION: Urology occupies a special place and remains a popular surgical speciality among students. Organization of practical sessions constitutes a solution to inform, create an emulation and motivate surgery interns to choose urology.