Pressure-and temperature-dependent luminescence from Tm^(3+) ions doped in GdYTaO_(4)

Luminescent properties of Tm^(3+)-doped GdYTaO_(4) are studied for exploring their potential applications in temperature and pressure sensing.Two main emission peaks from ^(3)H_(4)→^(3)H_(6) transition of Tm^(3+)are investigated.Intensity ratio between the two peaks evolves exponentially with temperature and has a highest sensitivity of 0.014 K^(−1) at 32 K.The energy difference between the two peaks increases linearly with pressure increasing at a rate of 0.38 meV/GPa.Intensity ratio between the two peaks and their emission lifetimes are also analyzed for discussing the pressure-induced variation of the sample structure.Moreover,Raman spectra recorded under high pressures indicate an isostructural phase transition of GdYTaO_(4) occurring at 4.46 GPa.

Influence of Polar Pressure Transmission Medium on the Pressure Coefficient of Excitonic Interband Transitions in Monolayer WSe_2

The influence of the pressure transmission medium（PTM）on the excitonic interband transitions in monolayer tungsten diselenide（WSe2）is investigated using photoluminescence（PL）spectra under hydrostatic pressure up to 5GPa.Three kinds of PTMs,condensed argon（Ar）,1：1 n-pentane and isopentane mixture（PM）,and4：1 methanol and ethanol mixture（MEM,a PTM with polarity）,are used.It is found that when either Ar or PM is used as the PTM,the PL peak of exciton related to the direct K-K interband transition shows a pressure-induced blue-shift at a rate of 32±4 or 32±1 meV/GPa,while it turns to be 50±9meV/GPa when MEM is used as the PTM.The indirect A-K interband transition presents almost no shift with increasing pressure up to approximatel.y 5 GPa when Ar and PM are used as the PTM,while it shows a red-shift at the rate of-17±7meV/GPa by using MEM as the PTM.These results reveal that the optical interband transitions of monolayer WSe2 are very sensitive to the polarity of the PTM.The anomalous pressure coefficient obtained using the polar PTM of MEM is ascribed to the existence of hydrogen-like bonds between hydroxyl in MEM and Se atoms under hydrostatic pressure.

Optical Properties of Atomic Defects in Hexagonal Boron Nitride Flakes under High Pressure

We investigate the pressure spectral characteristics and the effective tuning of defect emissions in hexagonal boron nitride(hBN) at low temperatures using a diamond anvil cell(DAC). It is found that the redshift rate of emission energy is up to 10 meV/GPa, demonstrating a controllable tuning of single photon emitters through pressure.Based on the distribution character of pressure coefficients as a function of wavelength, different kinds of atomic defect states should be responsible for the observed defect emissions.