Observation of Quantum Griffiths Singularity and Ferromagnetism at Superconducting LaAlO3/SrTiO3(110) Interface

Diverse phenomena emerge at the interface between band insulators LaAlO3 and SrTiO3, such as superconductivity and ferromagnetism, showing an opportunity for potential applications as well as bringing fundamental research interests. Particularly, the two-dimensional electron gas formed at LaAlO3/SrTiO3 interface offers an appealing platform for quantum phase transition from a superconductor to a weakly localized metal. Here we report the superconductor-metal transition in superconducting two-dimensional electron gas formed at LaAlO3/SrTiO3(110) interface driven by a perpendicular magnetic field. Interestingly, when approaching the quantum critical point, the dynamic critical exponent is not a constant but a diverging value, which is a direct evidence of quantum Griffiths singularity raised from quenched disorder at ultralow temperatures. Furthermore, the hysteretic property of magnetoresistance was firstly observed at LaAlO3/SrTiO3(110) interfaces, which suggests potential coexistence of superconductivity and ferromagnetism

Doppler Effect of Mechanical Waves and Light

We discussed the Doppler Effect of mechanical waves when the relative velocity is not in the direction of wave vector; and we found that the observed frequency changes with time, which is different from the results when the relative velocity is along the wave vector direction. We showed a simple derivation of Doppler Effect equation for the light by using time dilation principle and showed that the motion of light source and observer has the same effect on the frequency shift.El presente artículo presenta una discusión del Efecto Doppler en ondas mecánicas cuando se presenta una velocidad relativa que no se encuentra en dirección del vector de onda; se encontró que las frecuencias observadas varían respecto al tiempo, lo cual es diferente de los resultados respecto a la velocidad relativa a lo largo de la dirección del vector de onda. Se muestra una variación simple de la ecuación del efecto Doppler para la luz usando el principio de dilatación y mostrando que el movimiento de la fuente de luz y el observador presentan el mismo efecto en el cambio de frecuencia

Two forms of Wien's displacement law

The possible confusion of two form of Wien's law is clarified from the view points of physical significance and mathematics. In physics, because the spectral energy density distribution with frequency can't be simply converted to the distribution with wavelength by using c=ëf the wavelength corresponding to the maximum spectral energy density can�t be obtained by using m c / fm ë = where fm is the frequency corresponding to the maximum spectral energy density. In mathematics, because in the variables transformation from df to dëby using c=ëf there is an extra term �c/ë2 the spectral energy density function is changed, so is its maximum position. We use a simple parabolic distribution function as an example to explain this problem more clearly.La posible confusion de dos formas de la ley de Wien es clarificada desde los puntos de vista del significado fisico y matematico. En Fisica, debido a que la distribucion espectral de la energia con la frecuencia no puede simplemente ser convertida a la distribucion con longitud de onda usando c=�Éf la longitud de onda correspondiente al maximo de la densidad de energia espectral no puede ser obtenida por el uso de m c / fm �É = donde fm es la frecuencia correspondiente al maximo de densidad de energia espectral. En matematicas, debido a que en las variables de transformacion para pasar de df a d�É por el uso de c=�Éf hay un termino extra .c/�É2 la funcion de densidad de energia espectral es cambiada, asi tambien lo es su posicion maxima. Usamos una simple distribucion parabolica como ejemplo para explicar este problema mas claramente

A spin–orbit scattering–enhanced high upper critical field at the LaAlO3/KTaO3(111) superconducting interface

Spin–orbit interaction is essential to enhance the in-plane upper critical field of two-dimensional superconductors. Here, we report the LaAlO _3 /KTaO _3 (111) superconducting interface ( T _c,0 ≈ 0.475 K) with a high in-plane upper critical field (∼1.6 T), which is approximately 1.8 times the Pauli paramagnetic limit. The H $-$ T superconducting phase diagram is well-fitted by the Klemm–Luther–Beasley (KLB) theory, and the relevant spin–orbit scattering (SOS) length is approximately 32 nm. Furthermore, normal-state magnetotransport measurements show signatures of weak antilocalization caused by strong spin–orbit coupling in LaAlO _3 /KTaO _3 (111). The spin diffusion length derived from magnetotransport measurements was 40 nm at 2 K, which is comparable with the SOS length. The conformity of the phase diagram with the KLB theory and the consistency of normal state spin diffusion length and superconducting SOS length indicate that the high in-plane upper critical field at the LaAlO _3 /KTaO _3 (111) superconducting interface is enhanced by SOS