Ground-state properties of a triangular triple quantum dot connected to superconducting leads

We study ground-state properties of a triangular triple quantum dot connected to two superconducting (SC) leads. In this system orbital motion along the triangular configuration causes various types of quantum phases, such as the SU(4) Kondo state and the Nagaoka ferromagnetic mechanism, depending on the electron filling. The ground state also evolves as the Cooper pairs penetrate from the SC leads. We describe the phase diagram in a wide range of the parameter space, varying the gate voltage, the couplings between the dots and leads, and also the Josephson phase between the SC gaps. The results are obtained in the limit of large SC gap, carrying out exact diagonalization of an effective Hamiltonian. We also discuss in detail a classification of the quantum states according to the fixed point of the Wilson numerical renormalization group (NRG). Furthermore, we show that the Bogoliubov zero-energy excitation determines the ground state of a $\pi$ Josephson junction at small electron fillings.Comment: 6 pages, 7 figure

Field resilient superconductivity in atomic layer crystalline materials

The recent study [S. Yoshizawa et al., Nature Communications 12, 1 (2021)] reported the field resilient superconductivity, that is, the enhancement of an in-plane critical magnetic field $H^{||}_{\rm c2}$ exceeding the paramagnetic limiting field in an atomic layer crystalline ($\sqrt{7}\times\sqrt{3}$)-In on a Si(111) substrate. The present article elucidates the origin of the observed field resilient noncentrosymmetric superconductivity in the highly crystalline two dimensional material. We developed the quasiclassical theory by incorporating the Fermi surface anisotropy together with an anisotropic spin splitting specific to atomic layer crystalline systems. The enhancement of the rescaled $H^{||}_{\rm c2}$ by the critical temperature at zero field occurs not only due to the disorder effect but also to an anisotropic non-ideal Rashba spin texture depending on the field direction. We also study the parity mixing effect to show the enhancement of $H^{||}_{\rm c2}$ is limited in the moderately clean regime because of the fragile $s$-wave pairing against nonmagnetic scattering in the case of the dominant odd parity component of a pair wavefunction. Furthermore, from the analysis of the transition line, we identify the field resilience factor taking account of the scattering and suppression of paramagnetic effects and discuss the origin of the field resilient superconductivity. Through the fitting of the $H^{||}_{\rm c2}$ data, the normal state electron scattering is discussed, mainly focusing on the role of atomic steps on a Si(111) surface.Comment: 13 pages, 6 figures, 1 tabl

MIBG Predicts Falls in PD

Background: Falls are associated with poor prognosis in patients with Parkinson's disease (PD). Although several factors related to falls were reported in patients with PD, objective predictors of falls are not identified. We aimed to determine whether 123I-meta-iodobenzylguanidine (MIBG) cardiac scintigraphy could be a useful biomarker to predict falls. Methods: Forty-five patients with PD were enrolled in this study. These subjects were followed up more than 5 years after MIBG scintigraphy and were divided into two groups: one with decreased uptake of MIBG and the other without decreased uptake of MIBG. The cut-off value for the delayed heart-to-mediastinum ratio was 1.8. Kaplan-Meier analysis and a log-rank test were performed to test the predictive power of MIBG cardiac scintigraphy for falls. Univariate analysis was selected because we did not have appropriate data for adjustment, such as motor and cognitive assessment. Results: The group with decreased uptake of MIBG had a significantly higher incidence of falls than that without decreased uptake of MIBG (P = 0.022, log-rank test). Conclusions: Although the limitations of this study were lack of several key factors including motor and cognitive assessment, MIBG cardiac scintigraphy may be used to predict falls in patients with PD

A new quantitative index in the diagnosis of Parkinson syndrome by dopamine transporter single photon emission computed tomography

Objective Dopamine transporter single-photon emission computed tomography (DAT SPECT) has been widely used to diagnose Parkinson syndrome. Using the standardized uptake value (SUV) of DAT SPECT, we propose “functional dopamine transporter volume (f-DTV)” as a new quantitative index to evaluate the three-dimensional volume of functional dopamine transporters and assess its diagnostic ability in differentiating dopaminergic neurodegenerative diseases (dNDD) from non-dNDD. Methods Seventy-nine patients were enrolled (42 dNDD, 37 non-dNDD; 38 men; age, 24–88 years). We analyzed seven quantitative indices. The specific binding ratio (SBR) was calculated using a program specialized for DAT SPECT (SBR_Bolt). The SUVmax, SUVpeak, and SUVmean were calculated using a quantification program for bone SPECT. SBR_SUV was calculated by dividing striatal SUVmean by the average of background SUVmean. The cutoff value of the active dopamine transporter level was examined using three methods (threshold of 40% of SUVmax, SUV 2, and SUV 3) to calculate the active dopamine transporter volume (ADV). The f-DTV was calculated by multiplying ADV and SUVmean. We assessed the correlations between SBR_Bolt and SBR_SUV, and compared the mean value of each index between the dNDD and non-dNDD groups. The abilities of SBR_Bolt, SBR_SUV, SUVmax, SUVpeak, SUVmean, ADV, and f-DTV in differentiating dNDD from non-dNDD were determined by the area under the receiver operating curve (AUC) generated by the receiver operating characteristics analysis. Results The SBR_Bolt and SBR_SUV highly correlated each other (r = 0.71). The cutoff value of the active dopamine transporter level was determined as SUV 3. All seven quantitative indices showed lower values in the dNDD group than in the non-dNDD group, and the difference between the two groups was statistically significant (p<0.05). Sensitivity, specificity, and AUC of f-DTV were slightly lower than those of SBR_Bolt (71%, 79%, and 0.81, respectively, for f-DTV, and 81%, 84%, 0.88, respectively, for SBR_Bolt). The difference in AUC between f-DTV and SBR_Bolt was not statistically significant. Conclusions This study demonstrates the utility of f-DTV as a novel quantitative index for evaluating the three-dimensional volume of functional dopamine transporters, and that f-DTV has almost the same diagnostic ability to differentiate dNDD from non-dNDD using DAT SPECT