Unveiling the double-peak structure of quantum oscillations in the specific heat

Quantum oscillation phenomenon is an essential tool to understand the electronic structure of quantum matter. Here we report the first systematic study of quantum oscillations in the electronic specific heat $C_{el}$ in natural graphite. We show that the crossing of a single spin Landau level and the Fermi energy give rise to a double-peak structure, in striking contrast to the single peak expected from Lifshitz-Kosevich theory. Intriguingly, the double-peak structure is predicted by the kernel term for $C_{el}/T$ in the free electron theory. The $C_{el}/T$ represents a spectroscopic tuning fork of width 4.8 $k_B T$ which can be tuned at will to resonance. Using a coincidence method, the double-peak structure can be used to accurately determine the Lande $g$-factor of quantum materials. More generally, the tuning fork can be used to reveal any peak in fermionic density of states tuned by magnetic field, such as Lifshitz transition in heavy-fermion compounds.Comment: 22 pages, 5 figure

Is the Physiological Composition of the Vaginal Microbiome Altered in High-Risk HPV Infection of the Uterine Cervix?

Background: Cervical cancer is the fourth most common malignancy and fourth leading cause of cancer death in women worldwide. More than 99.7% of cases are caused by human papillomavirus (HPV), while HPV types 16 and 18 cause over 70% of all cervical cancer cases. In this preliminary study, we aimed to investigate the presence of HPV infection and diversity of bacteria associated with bacterial vaginosis. Methods: Cervical swabs (n = 21) taken from women aged 21–47 years, in seventeen cases, with different degrees of cervical abnormality, and from four healthy women, were tested for the presence of HPV DNA, as well as the bacterial strains associated with bacterial vaginosis, using the real-time PCR method. Results: HPV16 was the dominant genotype in 53% (9/17) of patients with confirmed precancerous lesions (ASCUS, LSIL, and HSIL). In specimens with confirmed cytological abnormalities and hrHPV infection, we detected a wide diversity of microbes, while the most common species were Gardnerella vaginalis, Atopobium vaginae, Prevotella bivia, Ureaplasma parvum, Ureaplasma urealyticum, Leptotrichia amnionii, Bacteroides ureolyticus, and Sneathia sanguinegens. The presence of pathogens did not differ, depending on the degree of precancerous lesions or HPV type. Conclusion: In our work, HPV16 dominated in patients with cervical precancerous lesions. We also suggest an increased bacterial diversity of the vaginal microbiome in patients with cervical lesions, for which the HPV virus is largely responsible

s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi3 single crystals

International audienceThe magnetic penetration depth $\lambda$ has been measured in MgCNi$_{3}$ single crystals using both a high precision Tunnel Diode Oscillator technique (TDO) and Hall probe magnetization (HPM). In striking contrast to previous measurements in powders, $\delta\lambda$(T) deduced from TDO measurements increases exponentially at low temperature, clearly showing that the superconducting gap is fully open over the whole Fermi surface. An absolute value at zero temperature $\lambda(0)=$230$\,$nm is found from the lower critical field measured by HPM. We also discuss the observed difference of the superfluid density deduced from both techniques. A possible explanation could be due to a systematic decrease of the critical temperature at the sample surface

Strongly dissimilar vortex-liquid regimes in single-crystalline NdFeAs(O,F) and (Ba,K)Fe2As2: A comparative study

International audienceThe extent of the vortex-liquid state in underdoped single crystals of the oxypnictide superconductors NdFeAs(O,F) and (Ba,K)Fe2As2 is investigated using specific heat (C-p) and Hall-probe magnetization experiments. In both materials, the vortex liquid lies entirely in the regime where the three-dimensional lowest Landau-level (3D-LLL) approximation is valid and both systems present a very small shift in the specific heat anomaly with increasing field. The irreversibility line, defined as the onset of diamagnetic response, is very rapidly shifted toward lower temperatures in NdFeAs(O,F) but remains close to the C-p anomaly in (Ba,K)Fe2As2. These measurements strongly suggest that a vortex-liquid phase occupies a large portion of the mixed-state phase diagram of NdFeAs(O,F) but not in (Ba,K)Fe2As2. This difference can be attributed to different Ginzburg numbers Gi, the latter being about 100 times larger in NdFeAs(O,F) than in (Ba,K)Fe2As2. The angular dependence of the upper critical field, derived from 3D-LLL scaling of the irreversibility lines, presents deviations from the standard 3D effective-mass model in both materials with an anisotropy being about three times smaller in (Ba,K)Fe2As2 (gamma similar to 2.5) than in Nd(F,O)FeAs (gamma similar to 7.5)