Electrical conductivity and charge density wave formation in 4HbTaS2under pressure

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Abstract
The two charge density wave (CDW) transitions in 4Hb TaS2 have been followed under pressure. The two transition temperatures were lowered when pressure was applied; the 315K atmospheric pressure transition associated with CDW formation in the octahedral layers was suppressed by 35 kbar, the 22K transition associated with CDW formation in the trigonal prismatic layers was suppressed at 8.5 kbar. The fall in the 22K transition correlates with the rise in superconducting transition temperature. The behaviour of the resistivity at the CDW transitions is discussed and charge transfer from the octahedral layers to the trigonal prismatic layers is proposed. The effect of pressure on CDW formation in trigonal prismatic material is related to its superconducting behaviour under pressure through the microscopic CDW theory of Chan and Heine (1973).