High pressure study of the normal and superconducting states of the layered pnictide oxide Ba_1−<i>x</i>Na_<i>x</i>Ti₂Sb₂O with<i>x</i>= 0, 0.10, and 0.15

Abstract

Here we present a systematic study of the effects of pressure on the\nsuperconducting and spin/charge density wave (SDW/CDW) transitions of\nBa$_{1-x}$Na$_x$Ti$_2$Sb$_2$O (x = 0, 0.10, and 0.15) by means of resistivity\nmeasurements. For x = 0 and 0.10, external pressure results in a decease of the\nSDW/CDW transition temperature T$_c$; however, no measurable change is observed\nfor the x = 0.15. The pressure effect on the superconducting transition\ntemperature is different for all three samples. For BaTi$_2$Sb$_2$O (x=0),\nT$_c$ increases significantly from 1.2 K at zero pressure to $\\sim$ 2.9 K at\n16.1 kbars. The 10 % Na-doped sample shows an initial T$_c$ increase up to 4.2\nK with pressure which saturates at higher pressure values. For higher Na\nconcentrations (x=0.15), T$_c$ continuously decreases with increasing pressure.\n