Chiral superfluid states in hybrid graphene heterostructures

The use of high quality hexagonal boron nitride (hBN) as a dielectric material has made possible the realization of graphene devices with very high mobility. In addition hBN can be made as thin as few atomic layers and, as recently demonstrated experimentally, can be used to isolate electrically two graphene layers only few nanometers apart. The combined use of graphene and hBN has therefore opened the possibility to create novel electronic structures. In this work we study the "hybrid" heterostructure formed by one sheet of single layer graphene (SLG) and one sheet of bilayer graphene (BLG) separated by a thin film of hBN. In general it is expected that interlayer interactions can drive the system to a spontaneously broken symmetry state characterized by interlayer phase coherence. The peculiarity of the SLG-BLG heterostructure is that the electrons in the layers (SLG and BLG) have different chiralities. We find that the difference of chirality between electrons in the two layers causes the spontaneously broken symmetry state to be N-fold degenerate. Moreover, we find that some of the degenerate states are chiral superfluid states, topologically distinct from the usual layer-ferromagnetism. The chiral nature of the ground state opens the possibility to realize protected midgap states. The N-fold degeneracy of the ground state makes the physics of SLG-BLG hybrid systems analogous to the physics of helium-3, in particular given the recent discovery of chiral superfluid states in this system.Comment: 5 pages, 4 figure

Surface States of Topological Insulators

We develop an effective bulk model with a topological boundary condition to study the surface states of topological insulators. We find that the Dirac point energy, the band curvature and the spin texture of surface states are crystal face-dependent. For a given face on a sphere, the Dirac point energy is determined by the bulk physics that breaks p-h symmetry in the surface normal direction and is tunable by surface potentials that preserve T symmetry. Constant energy contours near the Dirac point are ellipses with spin textures that are helical on the S/N pole, collapsed to one dimension on any side face, and tilted out-of-plane otherwise. Our findings identify a route to engineering the Dirac point physics on the surfaces of real materials.Comment: 4.1 pages, 2 figures and 1 tabl

A General Information Theoretical Proof for the Second Law of Thermodynamics

We show that the conservation and the non-additivity of the information, together with the additivity of the entropy make the entropy increase in an isolated system. The collapse of the entangled quantum state offers an example of the information non-additivity. Nevertheless, the later is also true in other fields, in which the interaction information is important. Examples are classical statistical mechanics, social statistics and financial processes. The second law of thermodynamics is thus proven in its most general form. It is exactly true, not only in quantum and classical physics but also in other processes, in which the information is conservative and non-additive.Comment: 4 page

Improving the Excited Nucleon Spectrum in Hard-Wall AdS/QCD

We show that the nucleon spectrum in a hard-wall AdS/QCD model can be improved by use of a relatively large IR cutoff. All of the spin-1/2 nucleon masses listed in PDG can be fit quite well within 11%. The average error is remarkably only 4.66%.Comment: 11 pages, 2 figures. v2: references added. v3: add a section about the pion-nucleon coupling, published versio

Hip Arthroscopic Surgery for Femoroacetabular Impingement: A Prospective Analysis of the Relationship Between Surgeon Experience and Patient Outcomes.

Background:Hip arthroscopic surgery is a rapidly growing procedure, but it may be associated with a steep learning curve. Few studies have used patient-reported outcome (PRO) surveys to investigate the relationship between surgeon experience and patient outcomes after the arthroscopic treatment of femoroacetabular impingement (FAI). Hypothesis:Patients undergoing hip arthroscopic surgery for the treatment of FAI in the early stages of a surgeon's career will have significantly worse outcomes and longer procedure times compared with patients treated after the surgeon has gained experience. Study Design:Cohort study; Level of evidence, 2. Methods:Patients undergoing hip arthroscopic surgery for FAI and labral injuries were prospectively enrolled during a sports medicine fellowship-trained surgeon's first 15 months of practice. Patients were stratified into an early group, consisting of the first 30 consecutive cases performed by the surgeon, and a late group, consisting of the second 30 consecutive cases. Radiographic and physical examinations were performed preoperatively and postoperatively. PRO surveys, including the 12-item Short Form Health Survey (SF-12), the modified Harris Hip Score (mHHS), and the Hip disability and Osteoarthritis Outcome Score (HOOS), were administered preoperatively and at a minimum of 1 year postoperatively. Results:There was no difference between the early and late groups for patient age (37.2 ± 11.5 vs 35.3 ± 10.8 years, respectively; P = .489), body mass index (25.6 ± 4.0 vs 25.1 ± 4.5 kg/m2, respectively; P = .615), or sex (P = .465). There was a significantly increased procedure time (119.3 ± 21.0 vs 99.0 ± 28.6 minutes, respectively; P = .002) and traction time (72.7 ± 21.4 vs 59.0 ± 16.7 minutes, respectively; P = .007) in the early group compared with the late group. Mean postoperative PRO scores significantly improved in both groups compared with preoperative values for all surveys except for the SF-12 mental component summary. No differences were found in PRO score improvements or complication rates between the early and late groups. Conclusion:The total procedure time and traction time decrease after a surgeon's first 30 hip arthroscopic surgery cases for FAI and labral tears, but patient outcomes can similarly improve regardless of surgeon experience in the early part of his or her career

Tunnelling of condensate magnetization in a double-well potential

We study quantum dynamical properties of a spin-1 atomic Bose-Einstein condensate in a double-well potential. Adopting a mean field theory and single spatial mode approximation, we characterize our model system as two coupled spins. For certain initial states, we find full magnetization oscillations between wells not accompanied by mass (or atom numbers) exchange. We identify dynamic regimes of collective spin variables arising from nonlinear self-interactions that are different from the usual Josephson oscillations. We also discuss magnetization beats and incomplete oscillations of collective spin variables other than the magnetization. Our study points to an alternative approach to observe coherent tunnelling of a condensate through a (spatial) potential barrier.Comment: 5 pages, 5 figures, submitted to Physical Review

Massive uncharged and charged particles' tunneling from the Horowitz-Strominger Dilaton black hole

Originally, Parikh and Wilczek's work is only suitable for the massless particles' tunneling. But their work has been further extended to the cases of massive uncharged and charged particles' tunneling recently. In this paper, as a particular black hole solution, we apply this extended method to reconsider the tunneling effect of the H.S Dilaton black hole. We investigate the behavior of both massive uncharged and charged particles, and respectively calculate the emission rate at the event horizon. Our result shows that their emission rates are also consistent with the unitary theory. Moreover, comparing with the case of massless particles' tunneling, we find that this conclusion is independent of the kind of particles. And it is probably caused by the underlying relationship between this method and the laws of black hole thermodynamics.Comment: 6 pages, no figure, revtex 4, accepted by Int. J. Mod. Phys