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Strain-induced splitting of the CCDW-NCCDW phase transition in 1T-TaS$_2$

M. M. Tyumentsev, V. E. Minakova, N. I. Fedotov, S. V. Zaitsev-Zotov

Abstract

The effects of uniaxial and biaxial tensile strain on the $ρ_{xx}$ and $ρ_{yy}$ components of the resistivity tensor, and the commensurable-nearly commensurate CDW (CCDW-NCCDW) transition temperature in 1T-TaS$_2$ are studied. At room temperature, uniaxial tensile strain increases the resistivity tensor components by a comparable magnitude both parallel and perpendicular to the strain axis. In the case of biaxial strain, up to 20~K decrease in the CCDW-NCCDW phase transition temperature is observed. In the case of uniaxial strain, a new phase with two different CCDW-NCCDW phase transition temperatures is observed, the splitting exceeds 10 K. The occurrence of such a phase is associated with the transition of the CDW into the commensurate state along the tensile strain direction while maintaining nearly commensurability along the perpendicular one. The results allow to justify various models widely used in analysis of transport properties of 1T-TaS$_2$ in commensurate and nearly commensurate states.

Strain-induced splitting of the CCDW-NCCDW phase transition in 1T-TaS$_2$

Abstract

The effects of uniaxial and biaxial tensile strain on the and components of the resistivity tensor, and the commensurable-nearly commensurate CDW (CCDW-NCCDW) transition temperature in 1T-TaS are studied. At room temperature, uniaxial tensile strain increases the resistivity tensor components by a comparable magnitude both parallel and perpendicular to the strain axis. In the case of biaxial strain, up to 20~K decrease in the CCDW-NCCDW phase transition temperature is observed. In the case of uniaxial strain, a new phase with two different CCDW-NCCDW phase transition temperatures is observed, the splitting exceeds 10 K. The occurrence of such a phase is associated with the transition of the CDW into the commensurate state along the tensile strain direction while maintaining nearly commensurability along the perpendicular one. The results allow to justify various models widely used in analysis of transport properties of 1T-TaS in commensurate and nearly commensurate states.
Paper Structure (4 sections, 5 equations, 6 figures)

This paper contains 4 sections, 5 equations, 6 figures.

Table of Contents

  1. Introduction
  2. Experimental methods
  3. Experimental results
  4. Discussion

Figures (6)

  • Figure 1: Temperature dependence of the resistivity of a bulk 1T-TaS$_2$ crystal. The arrows show directions of the measurements. Insets show STM images at in (a) NCCDW ($T=300$ K) and (b) CCDW ($T=78$ K) states. Scale bars are 5 nm.
  • Figure 2: Photos of the sample # 2 mounted on the biaxial tensile strain device at three different magnifications: a) The sample with contacts (scale bar is 200 $\mu$m); b) Polyimide cross with the sample on the heat exchange finger; contact numerations is shown by numbers (scale bar is 2 mm); c) Polyimide cross with the sample mounted in the tensile strain device (scale bar is 1 cm).
  • Figure 3: a) Step-like deformation applied sequentially along two axes; b) respective dependence of the resistances $R_x$, $R_y$ upon a step-like deformation change, measured in sample #1. Sample thickness = 280 nm. $T=300$ K.
  • Figure 4: Dependence of transition temperatures in 1T-TaS$_2$ on the nominal biaxial strain of the substrate for samples # 1 and # 2.
  • Figure 5: Temperature dependencies of the resistances $R_x$, $R_y$ measured in sample # 2 along orthogonal directions under various strains: a) relaxed sample, b) uniaxial strain, c) biaxial strain. The sample and axes are shown in Fig.\ref{['fig:samp']}.
  • ...and 1 more figures