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تسجيل مستخدم جديدTheory of charge density wave non-contact friction
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Franco Pellegrini
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A mechanism is proposed to describe the occurrence of distance-dependent dissipation peaks in the dynamics of an atomic force microscope tip oscillating over a surface characterized by a charge density wave state. The dissipation has its origin in the hysteretic behavior of the tip oscillations occurring at positions compatible with a localized phase slip of the charge density wave. This model is supported through static and dynamic numerical simulations of the tip surface interaction and is in good qualitative agreement with recently performed experiments on a NbSe$_2$ sample.
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Bulk electrical dissipation caused by charge-density-wave (CDW) depinning and sliding is a classic subject. We present a novel local, nanoscale mechanism describing the occurrence of mechanical dissipation peaks in the dynamics of an atomic force mic
roscope tip oscillating above the surface of a CDW material. Local surface 2$pi$ slips of the CDW phase are predicted to take place giving rise to mechanical hysteresis and large dissipation at discrete tip surface distances. The results of our static and dynamic numerical simulations are believed to be relevant to recent experiments on NbSe$_2$; other candidate systems in which similar effects should be observable are also discussed.
Bulk electrical dissipation caused by charge-density-wave (CDW) depinning and sliding is a classic subject. We present a novel local, nanoscale mechanism describing the occurrence of mechanical dissipation peaks in the dynamics of an atomic force mic
roscope tip oscillating above the surface of a CDW material. Local surface 2$pi$ slips of the CDW phase are predicted to take place giving rise to mechanical hysteresis and large dissipation at discrete tip surface distances. The results of our static and dynamic numerical simulations are believed to be relevant to recent experiments on NbSe$_2$; other candidate systems in which similar effects should be observable are also discussed.
We investigate the charge density wave transport in a quasi-one-dimensional conductor, orthorhombic tantalum trisulfide ($o$-TaS$_3$), by applying a radio-frequency ac voltage. We find a new ac-dc interference spectrum in the differential conductance
, which appear on both sides of the zero-bias peak. The frequency and amplitude dependences of the new spectrum do not correspond to those of any usual ac-dc interference spectrum (Shapiro steps). The results suggest that CDW phase dynamics has a hidden degree of freedom. We propose a model in which $2pi$ phase solitons behave as liquid. The origin of the new spectrum is that the solitons are depinned from impurity potentials assisted by an ac field when small dc field is applied. Our results provide a new insight as regards our understanding of an elementary process in CDW dynamics.
The quasi-one-dimensional (quasi-1D) TaSe3 attracts considerable attention for its intriguing superconductivity and possible interplay with nontrivial topology and charge density wave (CDW) state. However, unlike the isostructural analogues, CDW has
not been observed for TaSe3 despite its quasi-1D character that is supposed to promote Peierls instabilities and CDW. Here we synthesize TaSe3 mesowires (MWs) using a one-step approach. For the MW of ~300 nm thick, a distinct CDW transition occurs at 65 K in the resistivity measurement, which has not been reported before and is further evidenced by the Raman characterization and susceptibility measurement. For comparison, we have also prepared bulk single crystal TaSe3. Although no anomaly appears in the resistivity and magnetoresistance measurements, the carrier type detected by Hall effect varies from n-type to p-type below 50 K, suggesting a reconstruction of Fermi surface that could be associated with CDW. The enhancement of CDW in the MWs is attributed to the reduced dimensionality. TaSe3 is demonstrated to be a promising platform to study the correlation and competition of CDW and superconductivity in the quasi-1D systems.
The two charge-density wave (CDW) transitions in NbSe$_3$ %at wave numbers at $bm{q_1}$ and $bm{q_2}$, occurring at the surface were investigated by scanning tunneling microscopy (STM) on emph{in situ} cleaved $(bm{b},bm{c})$ plane. The temperature d
ependence of first-order CDW satellite spots, obtained from the Fourier transform of the STM images, was measured between 5-140 K to extract the surface critical temperatures (T$_s$). The low T CDW transition occurs at T$_{2s}$=70-75 K, more than 15 K above the bulk T$_{2b}=59$K while at exactly the same wave number. %determined by x-ray diffraction experiments. Plausible mechanism for such an unusually high surface enhancement is a softening of transverse phonon modes involved in the CDW formation.% The large interval of the 2D regime allows to speculate on % %the special Berezinskii-Kosterlitz-Thouless type of the surface transition expected for this incommensurate CDW. This scenario is checked by extracting the temperature dependence of the order % %parameter correlation functions. The regime of 2D fluctuations is analyzed according to a Berezinskii-Kosterlitz-Thouless type of surface transition, expected for this incommensurate 2D CDW, by extracting the temperature dependence of the order parameter correlation functions.
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