Abstract

Motivated by experiments on rhombohedral tetralayer graphene showing signs of superconductivity emerging from a valley-polarized normal state, we analyze theoretically how scanning tunneling spectroscopy can be used to probe the superconducting order parameter. We develop a microscopic tunneling approach that captures arbitrary, including finite-momentum, superconducting order parameters and low-symmetry normal-state Hamiltonians. We show that broken time-reversal symmetry in a single valley leads to distinctive weak-tunneling features for commensurate and incommensurate Cooper-pair momenta. We further uncover an unconventional spatial dependence of the Andreev conductance that can distinguish three topologically distinct classes of single-q pairing states, and compute signatures of a competing translational-symmetry-breaking three-q moiré superconductor.

Abstract

Motivated by experiments on rhombohedral tetralayer graphene showing signs of superconductivity emerging from a valley-polarized normal state, we analyze theoretically how scanning tunneling spectroscopy can be used to probe the superconducting order parameter. We develop a microscopic tunneling approach that captures arbitrary, including finite-momentum, superconducting order parameters and low-symmetry normal-state Hamiltonians. We show that broken time-reversal symmetry in a single valley leads to distinctive weak-tunneling features for commensurate and incommensurate Cooper-pair momenta. We further uncover an unconventional spatial dependence of the Andreev conductance that can distinguish three topologically distinct classes of single-q pairing states, and compute signatures of a competing translational-symmetry-breaking three-q moiré superconductor.

Abstract

Motivated by experiments on rhombohedral tetralayer graphene showing signs of superconductivity emerging from a valley-polarized normal state, we analyze theoretically how scanning tunneling spectroscopy can be used to probe the superconducting order parameter. We develop a microscopic tunneling approach that captures arbitrary, including finite-momentum, superconducting order parameters and low-symmetry normal-state Hamiltonians. We show that broken time-reversal symmetry in a single valley leads to distinctive weak-tunneling features for commensurate and incommensurate Cooper-pair momenta. We further uncover an unconventional spatial dependence of the Andreev conductance that can distinguish three topologically distinct classes of single-q pairing states, and compute signatures of a competing translational-symmetry-breaking three-q moiré superconductor.

Abstract

Motivated by experiments on rhombohedral tetralayer graphene showing signs of superconductivity emerging from a valley-polarized normal state, we analyze theoretically how scanning tunneling spectroscopy can be used to probe the superconducting order parameter. We develop a microscopic tunneling approach that captures arbitrary, including finite-momentum, superconducting order parameters and low-symmetry normal-state Hamiltonians. We show that broken time-reversal symmetry in a single valley leads to distinctive weak-tunneling features for commensurate and incommensurate Cooper-pair momenta. We further uncover an unconventional spatial dependence of the Andreev conductance that can distinguish three topologically distinct classes of single-q pairing states, and compute signatures of a competing translational-symmetry-breaking three-q moiré superconductor.