Thermal drag in spin ladders coupled to phonons

Abstract

We study the spin-phonon drag effect in the magnetothermal transport of spin-1/2 two-leg ladders coupled to lattice degrees of freedom. Using a bond operator description for the triplon excitations of the spin ladder and magnetoelastic coupling to acoustic phonons, we employ the time convolutionless projection operator method to derive expressions for the diagonal and off-diagonal thermal conductivities of the coupled two-component triplon-phonon system. We find that for magnetoelastic coupling strengths and diagonal scattering rates relevant to copper-oxide spin-ladders the drag heat conductivity can be of similar magnitude as the diagonal triplon heat conductivity. Moreover, we show that the drag and diagonal conductivities display very similar overall temperature dependences. Finally, the drag conductivity is shown to be rather susceptible to external magnetic fields.Comment: 9 pages, 4 figures, submitted to Phys. Rev.

Spin and thermal conductivity of quantum spin chains and ladders

“…In order to analyze the total thermal conductivity measured experimentally, one assumes κ total = κ ph + κ mag , where κ ph and κ mag represent the phononic and magnetic contribution, respectively. Such a separation is an approximation and should be understood as an operational means to extract mean-free paths -in general, spin-drag effects can lead to additional contributions to κ total [21,23,25]. In the high-temperature limit, one needs to keep only the leading terms in a 1/T expansion of Eqs.…”

“…The contribution of magnetic excitations to the full thermal conductivity in these low-dimensional systems manifests itself via a prominent anisotropy of the thermal conductivity measured along different crystal axes [16,17]. Open and timely questions include a comprehensive and quantitative theoretical explanation for the magnitude of the thermal conductivity, a theory of relevant scattering channels beyond pure spin systems (see, e.g., [20][21][22][23][24][25][26]), a full understanding of the spin-phonon coupling including spin-drag effects [23][24][25], and the understanding of a series of experiments studying the effect of doping with nonmagnetic or magnetic impurities and disorder onto the thermal conductivity (see, e.g., [111,112]). Here we solely focus on pure spin Hamiltonians.…”

“…18 and 19 for a review), which is further complicated by the need to account for phonons and impurities (see Refs. [20][21][22][23][24][25][26] for work in this direction).…”

Real-time and real-space spin and energy dynamics in one-dimensional spin-12systems induced by local quantum quenches at finite temperatures

“…64 While it is tempting to relate the experimental observation of large thermal conductivities in certain spinchain materials [58][59][60] to conserved currents for the underlying spin Hamiltonians, many other effects need to be taken into account to obtain a full description, including phonons, [65][66][67][68] impurities, [69][70][71] or spin-drag effects. 68,72 It is at present still an open question whether anomalous transport due to exact conservation laws of onedimensional spin models survives these perturbations in such a way that the proximity of a realistic system to integrable models can be viewed as the core reason for the large one-dimensional heat conductivities.…”

Proposal for measuring the finite-temperature Drude weight of integrable systems

“…While the prediction of anomalous transport in integrable models is very intriguing, its direct relevance to solid-state experiments is unclear since there, external scattering channels such as phonons or impurities will usually dominate the behavior [49][50][51][52][53][54]. Nevertheless, there has been an impressive series of experiments focussing mostly on thermal transport in quantum magnets [55][56][57][58][59][60][61][62][63][64][65][66][67][68], reporting remarkably large thermal conductivities in 1D systems [55,69].…”