arXiv subjects

Indranil Paul

Publications and source records attributed to Indranil Paul.

21 records · Page 2Linked to original sources

arXiv2002

Structural Transition of Wigner Crystal on Liquid Substrate

The physics of an electron solid, held on a cryogenic liquid surface by a pressing electric field, is examined in a low-density regime that has not been explored before. We consider the effect of the pressing field in distorting the surface at the position of each electron and hence inducing an attractive force between the electrons. The system behavior is described in terms of an interplay between the repulsive Coulomb interaction and the attractive surface-induced interaction between individual electrons. For small densities and large enough pressing fields, we find a parameter regime where a square lattice is more favorable than the usual triangular lattice; we map out the first-order transition curve separating the two lattice geometries at zero temperature. In addition, our description allows an alternate static perspective on the charge-density wave instability of the system, corresponding to the formation of multi-electron dimples.

cond-mat.mes-hall↗

arXiv2002

Thermal Transport for Many Body Tight-Binding Models

We clarify some aspects of the calculation of the thermal transport coefficients. For a tight-binding Hamiltonian we discuss the approximate nature of the charge current and the thermal current obtained by Peierls substitution which is also identical to the equation of motion technique. We address the issue of choosing an appropriate basis for making the Peierls construction for transport calculations. We propose a criteria for finding an optimum Wannier basis where the difference between the exact current and the approximate one is minimum. Using the equations of motion we derive the thermal current for a generalized Hubbard model with density interaction. We identify a part which is the contribution from the long range interactions to the heat current. For the Hubbard model we derive expressions for the transport coefficients in the limit of infinite dimensions.

cond-mat.str-el↗

arXiv2002

Thermoelectric Behaviour Near Magnetic Quantum Critical Point

We use the coupled 2d-spin-3d-fermion model proposed by Rosch {\sl et. al.} (Phys. Rev. Lett. {\bf 79}, 159 (1997)) to study the thermoelectric behaviour of a heavy fermion compound when it is close to an antiferromagnetic quantum critical point. When the low energy spin fluctuations are quasi two dimensional, as has been observed in ${\rm YbRh}_2{\rm Si}_2$ and $ {\rm CeCu}_{6-x}{\rm Au}_x $, with a typical 2d ordering wavevector and 3d Fermi surface, the ``hot'' regions on the Fermi surface have a finite area. Due to enhanced scattering with the nearly critical spin fluctuations, the electrons in the hot region are strongly renormalized. We argue that there is an intermediate energy scale where the qualitative aspects of the renormalized hot electrons are captured by a weak-coupling perturbative calculation. Our examination of the electron self energy shows that the entropy carried by the hot electrons is larger than usual. This accounts for the anomalous logarithmic temperature dependence of specific heat observed in these materials. We show that the same mechanism produces logarithmic temperature dependence in thermopower. This has been observed in $ {\rm CeCu}_{6-x}{\rm Au}_x $. We expect to see the same behaviour from future experiments on ${\rm YbRh}_2{\rm Si}_2$.

cond-mat.str-el↗