Relaxation time spectrum of low-energy excitations in one- and two-dimensional materials with charge or spin density waves

Abstract

The long-time thermal relaxation of (TMTTF)2Br, Sr14Cu24O41 and Sr2Ca12Cu24O41 single crystals at temperatures below 1 K and magnetic field up to 10 T is investigated. The data allow us to determine the relaxation time spectrum of the low energy excitations caused by the charge-density wave (CDW) or spin-density wave (SDW). The relaxation time is mainly determined by a thermal activated process for all investigated materials. The maximum relaxation time increases with increasing magnetic field. The distribution of barrier heights corresponds to one or two Gaussian functions. The doping of Sr14−xCaxCu24O41 with Ca leads to a drastic shift of the relaxation time spectrum to longer time. The maximum relaxation time changes from 50 s (x = 0) to 3000 s (x = 12) at 0.1 K and 10 T. The observed thermal relaxation at x=12 clearly indicates the formation of the SDW ground state at low temperatures.

Impurities in the weakly coupled quantum spin chains Sr2CuO3 and SrCuO2

“…Since our measurements along both the orientations were performed on same crystal specimen, the minor differences at low-temperatures, in particular in the zero-field data, are not intrinsic. From previous investigations it is known that in insulating magnetic crystals (e.g., the spin ice compound Dy 2 Ti 2 O 7 37 and several low-dimensional quantum magnets 38 ), the slow relaxation of low-energy excitations can introduce some dependence of the measured specific heat on extrinsic parameters, such as, the measurement duration, thermal anchoring of the sample, applied magnetic field, etc. 38,39 .…”

“…From previous investigations it is known that in insulating magnetic crystals (e.g., the spin ice compound Dy 2 Ti 2 O 7 37 and several low-dimensional quantum magnets 38 ), the slow relaxation of low-energy excitations can introduce some dependence of the measured specific heat on extrinsic parameters, such as, the measurement duration, thermal anchoring of the sample, applied magnetic field, etc. 38,39 . A combination of these factors might be related to the observed orientation dependence of specific heat at low-temperatures.…”

Impurities in weakly coupled quantum spin chains Sr$_{2}$CuO$_{3}$ and SrCuO$_{2}$

“…Since our measurements along both the orientations were performed on same crystal specimen, the minor differences at low-temperatures, in particular in the zero-field data, are not intrinsic. From previous investigations it is known that in insulating magnetic crystals (e.g., the spin ice compound Dy 2 Ti 2 O 7 37 and several low-dimensional quantum magnets 38 ), the slow relaxation of low-energy excitations can introduce some dependence of the measured specific heat on extrinsic parameters, such as, the measurement duration, thermal anchoring of the sample, applied magnetic field, etc. 38,39 .…”

“…From previous investigations it is known that in insulating magnetic crystals (e.g., the spin ice compound Dy 2 Ti 2 O 7 37 and several low-dimensional quantum magnets 38 ), the slow relaxation of low-energy excitations can introduce some dependence of the measured specific heat on extrinsic parameters, such as, the measurement duration, thermal anchoring of the sample, applied magnetic field, etc. 38,39 . A combination of these factors might be related to the observed orientation dependence of specific heat at low-temperatures.…”