GPUQT: An efficient linear-scaling quantum transport code fully implemented on graphics processing units

Abstract

We present GPUQT, a quantum transport code fully implemented on graphics processing units. Using this code, one can obtain intrinsic electronic transport properties of large systems described by a real-space tight-binding Hamiltonian together with one or more types of disorder. The DC Kubo conductivity is represented as a time integral of the velocity auto-correlation or a time derivative of the mean square displacement. Linear scaling (with respect to the total number of orbitals in the system) computation time and memory usage are achieved by using various numerical techniques, including sparse matrix–vector multiplication, random phase approximation of trace, Chebyshev expansion of quantum evolution operator, and kernel polynomial method for quantum resolution operator. We describe the inputs and outputs of GPUQT and give a few examples to demonstrate its usage, paying attention to the interpretations of the results. Program summaryProgram Title: GPUQTProgram Files doi:http://dx.doi.org/10.17632/xbf5kbkzx7.1Licensing provisions: GPLv3Programming language: CUDANature of problem: Obtain intrinsic electronic transport properties of large systems described by real-space tight-binding Hamiltonians.Solution method: The DC conductivity is represented as a time integral of the velocity auto-correlation (VAC) or a time derivative of the mean square displacement (MSD). The calculations achieve linear scaling (with respect to the number of orbitals in the system) computation time and memory usage by using various numerical techniques, including sparse matrix–vector multiplication, random phase approximation of trace, Chebyshev expansion of quantum evolution operator, and kernel polynomial method for quantum resolution operator.Restrictions: The number of orbitals is restricted to about 20 million due to the limited amount of device memory in current GPUs.