First principles study and comparison of vibrational and thermodynamic properties of XBi(X=In,Ga,B,Al)

In the present work, vibrational and thermodynamic properties of XBi（X = B, Al, Ga, In） compounds are compared and investigated. The calculation is carried out using density functional theory（DFT） within the generalized gradient approximation（GGA） in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory（DFPT） as implemented in Quantum ESPRESSO（QE） code. Thermodynamic properties involving phonon density of states（DOS） and specific heat at constant volume are investigated using quasiharmonic approximation（QHA） package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm^-1, 150 cm^-1, 300 cm^-1, and 150 cm^-1, respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T-3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.

Deterministic loading of an individual atom:Towards scalable implementation of multi-qubit

We report the realization of a deterministic single-atom preparation by the method of all-optical feedback. Using a fast-real-time feedback, the light-induced atom desorption effect and blue detuned light-induced atom collision process can increase a success probability of single-atom preparation up to more than 99%. We investigate the dynamics of loading single atom trapped in a trap with a size of hundreds of micrometers into a pair of microscopic tweezers. The detailed experimental results show that the feedback loading is spatially insensitive, which implies that it is possible to use the feedback protocol to simultaneously implement the loading of large number of qubits arrays.

Gd^(3+) ion induced UV upconversion emission and temperature sensing in Tm^(3+)/Yb^(3+):Y_(2)O_(3) phosphor

Cubic phase Tm^(3+)/Yb^(3+):Y_(2)O_(3) and Tm^(3+)/Yb^(3+)/Gd^(3+):Y_(2)O_(3) phosphors were prepared by low temperature combustion technique for upconversion emission in UV-visible range.The 980 nm excitation has generated UV emission at 314 nm in tridoped phosphor due to the energy transfer from Tm^(3+) to Gd^(3+)ion.Characteristic emission bands from Tm^(3+) are also observed in both the phosphors.Thermally coupled Stark sublevels ^(1)G_(4(a))(476 nm) and ^(1)G_(4(b))(488 nm) of Tm^(3+) ion were utilised for optical thermometry using fluorescent intensity ratio(FIR) method.The result shows that maximum absolute sensitivity in tridoped phosphor is observed to be 1.33 × 10^(-3) K^(-1) at 298 K.Moreover,temperature rise of phosphor at various pump power densities was also measured and it is estimated to achieve 407 K at the pump power density of 38.46 W/cm^(2).